Dangers to Earth from Ancient Supernovas and Supernova Ejecta and the Dangers to Earth Introduction The following combines two articles that were originally published as webpages to illustrate the possible source of high-energy phenomena from space that would have the potential to change the Earth’s rotation axis – yet without leaving any physical scar on the surface. The articles are not primarily written for astronomers (although I hope they would find the discussion of interest) but for the interest of the general reader and the catastrophist researcher. The articles build on the concepts touched-upon in my 2006 book: Under Ancient Skies. [1] I hope that the discussion here will give some answer to those nineteenth-century academics who declared that pole-shifts and axis-tilts cannot happen; negative pronouncements that even today hold back discussion by modern science. The first article concentrates primarily upon the dangers posed by fast supernova ejecta, while the second also briefly explores other high-energy phenomena recently discovered by astronomers. Thanks to new space-based telescopes, the discoveries are coming so fast that they appear in publication faster than one can write about them. The possibility and likelihood of pole shifts or changes to the Earth’s obliquity (axis tilts) were advanced by various enthusiasts during the twentieth century, principally following the dubious astronomy of Ivan Velikovsky or the ‘crustal slippage’ ideas of Charles Hapgood – or even Dodwell’s unpublished proof of the Bible. All of these were based on 1950’s science predating many of the scientific advances in geology and astronomy from the 1960s onwards, yet they continue to appear in ‘popular’ science books up to the present day. Many of these modern authors fail to appreciate that a pole shift and an axis tilt are not the same thing at all and have quite different causes. At the base of scientific scepticism lie the pronouncements of eminent nineteenth century and early twentieth century physicists. Note as a typical example the remarks made in 1876 by Sir John Evans; the eminent Professor Twisden; and (below) the Reverend Hill, then a physics tutor at Cambridge: Internal changes cannot alter the axis, only the distribution and the motion of matter about it. If the mass began to revolve about a new axis, every particle would begin to move in a new direction. What is there to cause this? When a cannon ball strikes a metal plate obliquely, the shock may deflect it into a new direction. The Earth’s equator is moving faster than a cannon ball. Where is the force that could deflect every portion of it and every portion of the Earth into new directions of motion? [2] Also since the 1960s the study of the Earth’s free wobble modes: the Chandler wobble and the Core wobble have advanced to a point where we may see more clearly the forces that are needed to trigger them. The Chandler wobble is observed to cause small pole shifts and is triggered by internal changes in the mass distribution of the planet; The Core wobble requires a substantial external force from space to excite it but it could trigger a change of the obliquity. We therefore need to investigate what those forces from the wider cosmos might be. 1 Dunbavin, Paul (2006) Under Ancient Skies, Ancient Astronomy and terrestrial Catastrophism, Third Millennium, Nottingham ISBN: 0-9525029-2-5 2 Evans, J. Quart. Journ. Geol. Soc. 1876, xxxxii, proc., p108 (and later responses) Dangers to Earth from Ancient Supernovas Paul Dunbavin (2019) Summary: This article is less about supernovas and star-mergers themselves, rather the possibility of fast-ejecta from them impacting the Earth. For the benefit of the general reader scientific terms are kept to a minimum and explained where necessary or may be pursued in the suggested links. Astrophysical research papers are not usually written for the benefit of the general reader or even for the cross-disciplinary researcher, but for their specialist colleagues. It should not therefore be assumed that the present author fails to understand the terminology and equations in the cited sources; but neither should it be assumed that he understands all of them! In proposing a theory that the Earth’s axis has changed in recent prehistory – be it either a pole-shift or a more extensive change to the obliquity or length-of-day – requires a mechanism to explain how it could happen; the question cannot be ducked. Even a giant asteroid impact like that which caused the extinction of the dinosaurs would not possess enough energy to significantly disturb the Earth’s axis and rotation. This has long been sufficient cause for geologists and physicists to dismiss the entire subject of pole shifts and axis-tilts as pseudo-science. The historiography of this subject was discussed in my book Under Ancient Skies. It is true; there have been many naïve pole-shift theories which do not acknowledge the vast energy that would be required. Yet there are clues that something did disturb the Earth’s rotation at the close of the ice-age and also again in the mid-Holocene (see: Raised Beaches and Submerged Forests - Curious Anomalies) To propose a theory of changes to the axis requires an external force that could significantly alter the Earth’s angular momentum yet without leaving an obvious impact scar; and without causing a mass extinction event. As discussed in Under Ancient Skies there are three principal candidates that might offer an answer to this conundrum: 1) Small-fast meteors ejected by ancient supernovae, stellar mergers and active galaxies. 2) Gravitational waves from mergers of compact stars in the close solar neighbourhood. 3) As yet unknown physics: dark-matter; gravity leaking from parallel universes, etc. Here we shall discuss only the first possibility. Since the 1990s there has been much discussion of the collision dangers from near-earth asteroids that we could detect. These might destroy cities and create dust-veils but would not possess enough energy to significantly change the axis of rotation. Comets could strike with higher velocities up to 72 km/sec for a head-on collision – but while calamitous for all life, even this would not be enough to make the world wobble on its axis. Fast hyperbolic asteroids like Oumuamua that may have been ejected from other solar systems may travel even faster, but they still do not possess enough energy. Kinetic energy increases with mass, but with the square of the velocity (E=1/2mv2) and so the real danger comes from small fast objects potentially ejected by ancient supernovas. To experiment with the scale of this you may like to try-out this useful calculator tool: A little experimentation will show that the velocity of the comet would need to be travelling at a significant fraction of the speed of light to approach the kinetic energy of the Earth’s rotation, calculated at 2.138x1029 joules. Could a supernova or a stellar-merger send objects of such relativistic velocities in our direction? Might they reach us from even more distant active galaxies? The origin of the charged particles in cosmic-rays from such events is generally accepted, but the possibility of more substantial pieces of high-energy matter is more speculative. See for example this example from a 2014 discovery. Astronomers identify two classes of stars that explode as supernovae. The first is ‘core collapse’ (types II, 1b and 1c); these are massive stars that leave a compact remnant of some kind, a pulsar or a black hole. Typical examples of this type would be the Crab Nebula in the constellation Taurus and its central pulsar; or SN1987A which exploded in the Large Magellanic Cloud in 1987; the most recent that has been observed in our Galactic neighbourhood. The Crab pulsar is observed to rotate 33 times per second, and the surrounding nebula is expanding at about 1500 km/s. Another example would be Cassiopeia A, a strong X-ray source, which should have been first-visible from Earth around 340 years ago but went unrecorded. The remnant is seen to be expanding away from a central pulsar at: “up to 31 million miles per hour [13800 km/s] (fast enough to travel from Earth to the Moon in 30 seconds!)”. For more information about Cassiopeia A, see this example from a NASA website which includes a Hubble photo. The second class of supernova is a ‘thermonuclear explosion’ (type 1a); less powerful but likely to be more common. We may compare these to a vast nuclear bomb. They are believed to be white dwarf stars that have accreted a shell of matter, usually pulled from a close companion star. When they reach maximum size (Chandrasekhar limit) they must contract further to a neutron star but this can cause a thermonuclear runaway that completely disrupts the progenitor star. They leave no central remnant behind and by definition they should all be of a similar energy. Tycho’s supernova SN1572 is one example, whose visible remnant has been variously calculated to be expanding asymmetrically at between 5,000 and 9,000 km/sec. [1] Another instance of this type of explosion within a close-binary system may be Kepler’s supernova of 1604, but its cause remains uncertain – a possible merger of two white dwarfs. SN1604 is described by astronomers as having been ‘unusually powerful’.[2] However, the estimated rate of expansion is comparatively low at 4200 km/s [3]. The recently discovered SNIa G1.9 + 03 may be another example of this type. Astronomers observe that stars don’t just explode without warning. Massive stars approaching their crisis will be surrounded by a dense planetary nebula ejected by novae in the later phases of their evolution. Within and beyond this will be the cloud of planetesimals, asteroids, meteors and comets that have circled the star ever-since it formed, equivalent to the Oort cloud around our Sun. These bodies are too small be detected but we know they must be present. Consider how many billions of icy comets and small asteroids orbit our own sun, completely unseen until one of them streaks through the sky as a comet. A prime example of an ‘overdue’ supernova is the star Eta Carinae, which survived a nova explosion observed in 1843 (a supernova ‘imposter’). The ejected matter is seen to be travelling at 32 million kilometres per hour! Astronomers cannot explain how the central star survived the nova as it is burning heavy elements in its core, its hydrogen fuel – long gone. It makes a startling image in the Hubble photographs. Fascinating as these spectacular examples are, it is probably the closer and less spectacular supernova remnants, those we can no longer see, which offer the more likely danger to us on Earth. The final collapse of a massive star occurs within a fraction of a second as it exhausts its silicon and lighter elements and has only iron remaining in its core. This cannot release further energy from nucleosynthesis to support itself and can only collapse down to incredible density as the iron is crushed to a rapidly-spinning ball of neutrons – a neutron-star. You may wonder how a collapse can cause an explosion. Various mechanisms are proposed and need not be discussed in detail here as we are more concerned with the remnant rather than the explosion. Most often discussed is that the collapsing matter ‘rebounds’ from the dense nucleus and collides with the in-falling matter triggering nuclear synthesis; and that the resulting burst of radiation and neutrinos would blow away the shell of the star. However another theory considers that the principle mechanism could be the rapid spinning-up of the core as it forms the central pulsar or black-hole; this throws-out the neutron-rich matter and the collapsing shell, in what is sometimes termed a ‘sausage instability’ (mass-shedding via outgoing spiral arms of matter). [4] Remember this all occurs within a fraction of a second! A naive illustration would be to swing a string of sausages round your head – it is the fast-moving outer links that are most likely to fly-off at a tangent! These ejecta collide with the in-falling stellar envelope and triggers further synthesis of heavy elements and vast release of radiation that we observe. The energy is carried away in a shock-wave that sweeps up everything surrounding the star and creates the visible nebula. The expansion of the ejected remnant then proceeds as the supernova fades. We may propose that when the shocked ejecta reaches the outer shell of meteors, asteroids and icycomets surrounding the exploding star then these would be disrupted into smaller fragments. Usually astronomers consider total disruption to gas and dust; and that the expansion ceases when the mass of the surrounding shell equals that of the unshocked interstellar medium. This may be so for most of the mass. However, bodies of optimum size and distance from the explosion may not be disrupted completely. If the explosion has enough energy to disrupt an asteroid then it must also be sufficient to propel away the fragments. Much depends upon how fast the collapsar is spinning. There is nothing in the interstellar vacuum of space that could then impede this shell of ejected meteors from expanding to infinity unless they encounter the gravity of another massive body (i.e. a star or planet). [A crude analogy for the non-astrophysicist: consider your garden blower as it easily blows-away the sand and leaves; the blower is strong and the leaves are light. However, if someone throws a pebble at you could you deflect it away with your leaf-blower? I don’t think so! How strong would your blower need to be; and how small must be the projectile for the blower to have any effect? How hard would you need to blow to completely disrupt the pebble?] A further source of fast ejecta from a supernova may originate from neutron-matter expelled from the dense core as it spins-up. Astronomers theorise that such matter should very rapidly decompress to heavy nuclei (r-process elements) and iron. Again, these are likely to clump rather than persist as dust and gas. Sometimes trails can be observed within supernova remnants, which are interpreted as fragments from the core travelling through the gaseous remnant. For each of these there must be many smaller unobservable clumps. What is to impede these ejected pseudo-comets from escaping to great distances? A complex collection of supernova remnants of various ages are found in the Vela nebula, revealed in a striking composite picture released by NASA. You may also like to read the interesting study of the vela complex by Bill Blair. If we take as an example the paper by Loeb-et-al; the authors consider the V-shaped wakes observed within the Vela supernova remnant that are loosely estimated to be moving away at around 3000 km/s. [5] They demonstrate that these could not be the ejected former planets of the parent star, as these should be totally disrupted and would long-since have faded from view. At the point where the fragments cease to be observable, the professional astronomers lose interest; the planetary fragments are assumed to vanish into the supernova remnant. The disrupted planetary fragments, travelling at even a fraction of the remnant’s expansion velocity, are still very fast compared to solar comets. Rather, the authors consider that the observed high-velocity fragments are more likely to have been formed in the dense core and then ejected as the central remnant spins-up (an asymmetric gravitational collapse). The neutronic matter re-forms into heavy nuclei, principally iron and nickel – but unlike a solar iron meteorite these should also contain short-lived isotopes of heavy elements and iron-60. The authors consider that there must be “many more, smaller fragments” that we cannot detect. [6] Again the professional astronomer seems to lose interest if the bodies are too small to be detectable with telescopes. In fact, the diffuse shell must continue to expand long after the remnant has faded and they will one-day reach us. How many other expanding shells of older supernovas are out there, whose nebulae have faded from view? Their ‘comets’ are still on their way towards us or have already passed through the solar system. Until quite recently, astrophysicists believed that all the elements heavier than iron were created in supernova explosions. However, it is now accepted that even the high density of a supernova corecollapse is not dense enough for the r-process to create these elements. To produce these requires the merger of two neutron-stars, or perhaps a neutron star and a white dwarf. These events generate intense magnetic fields that fling jets of matter away from both poles of the collapsing star at nearrelativistic speeds. These are also now believed to be the source of the gamma-ray bursts observed in distant galaxies; the bursts that are detected come from chance events where the polar jets are pointed directly at us. It is reasonable to expect that iron-rich meteor fragments might also be accelerated away by these intense magnetic fields. The next problem to consider is how often we may expect to encounter the diffuse shells of fastmoving meteors and comets; and how may we observe them in order to prove their existence? In our historical records, visible supernovae have occurred about ever 300-500 years on average, the most recent being that observed by Kepler in 1604. In all, there should be about two events per century for the Milky Way galaxy, which would give the above average for our observable region. [7] Events on the far side of the galaxy should represent no danger to us. Therefore, the expanding shells of ancient ejecta should arrive at the solar system with a similar regularity to the observed supernova events. Between these episodes we are unlikely to encounter supernova ejecta and it may be that no such encounter has occurred since the advent of telescopic astronomy. In most events, they may be expected to rapidly pass through the solar system without hitting a planet. Therefore we may postulate a collision-event perhaps every few thousand years; really energetic axis-tilting events should be even less common by a multiple of 180. Without precise observational data to cite, the speculation flag will inevitably be raised! When astronomers and popular commentators discuss the dangers from supernovas they tend to seek those that may explode within say, 500 light-years – the solar neighbourhood, such as the bright star Betelgeuse in Orion. The popular view is that as long as the supernova is more than say, 50 light-years away then we should be safe. The focus falls upon the gamma-ray burst or the intense flash of cosmic radiation and neutrinos that might reach us at the same time as we see its light; some others may consider the ‘bubble’ of charged particles, travelling typically at a fraction of light-speed that should reach us a few hundred years later. By contrast, many thousands of years may pass for the hypervelocity solid ejecta to reach us from stellar explosions. However, we may get some advance warning. The charged particles from the supernova, travelling at a fraction of the speed of light, should reach us well in advance of the solid bodies; we should therefore observe a change in the background cosmic ray flux. Perhaps astronomers could then calculate their point of origin and predict when the dangerous ‘comets’ will arrive. Then what should we do? A flux of small-fast-comets arrives at the Earth. This illustration was figure 10.1 of Under Ancient Skies We should also consider what the impact of a small-fast meteor on the Earth might look like; take as an example, a football-sized icycomet, perhaps with a solid core, travelling at the ejected supernova velocities discussed above. The composition is irrelevant, ice would be just as destructive as iron; it is the velocity that supplies the kinetic energy not the mass. There is no ideal research to cite here as such impacts have not been much considered by specialists. The best one can suggest is that it would drill deep into the crust, more like a bullet-hole than an impact crater. The impact would throw-out a tail of terrestrial rock far exceeding the small mass of the projectile, which would then dissolve deep within the earth. The best research we can consider would be the various theories for the formation of tektites, where we find strewn fields of these tiny impact-ejecta that are considered to be shocked glass formed from melted sedimentary rock as it re-enters the atmosphere. [8] Other than the tektites very little evidence would remain after a few thousand years; no crater, no tell-tale layer of Iridium, no evidence of a dust veil. We might however expect to find traces of heavy elements, and rare radioactive isotopes around the impact site – if we could find one! The consensus seems to be that very special and seldom-encountered high-energy events are required to explain the composition of tektites. For further information, the reader may like to pursue the following links: a basic introduction plus a more scholarly article: Conclusions A high energy impact event has the capacity to supply an impulse of kinetic energy in the direction of its travel. Depending upon the size, direction and velocity, this has the capacity to change the Earth’s angular momentum; and to excite the Chandler Wobble. Without ‘hard’ evidence then all we should expect to see in the geological record of the recent-past is evidence of the transient wobble and a pole shift; perhaps: a change of obliquity and a glitch in the length of the day. We might expect these effects to be of the order of arc-seconds or arc-minutes at most, but enough to be noticeable. This would manifest as sea-level and climate oscillations in the recent geological record; and in transitions from one stable regime to another. However, it must be stressed again that in order to change the Earth’s angular momentum by any significant amount, say, measured in full degrees or arc-minutes of latitude, then the impactor must arrive at a very high velocity perhaps approaching half the speed of light; and it would also have to be very small were it not also to cause a mass extinction event. To create impactors of such high energy we may therefore narrow down the source to those smaller chunks of heavy elements and iron ejected from the core of a supernova or star-merger event during its collapse. The only other source powerful enough might be the relativistic jets ejected from the poles of the collapsar during its rapid contraction phase; and one would have to be pointing in our direction from an ancient event. If it were closer then we could not escape the even more destructive effects of the gamma-rays! If something like this did reach us during Earth’s recent prehistory then astronomers should one-day be able to identify a candidate progenitor star, which should by now be detectable as a black-hole. Unfortunately, evidence of sea level and climate oscillations in recent prehistory can also be explained by other causes; and so without a clear worldwide pattern the sceptical geologists and climate specialists will not be convinced of catastrophic events from space. Astrophysicists are more openminded; they are accustomed to discussing hypothetical phenomena that they can’t touch; but geologists: they study rocks and they drill holes; it can be difficult to persuade them to look upwards. Relevant Hyperlinks https://www.calculatorsoup.com/calculators/physics/kinetic.php https://www.sciencemag.org/news/2014/07/physicists-spot-potential-source-oh-my-god-particles https://svs.gsfc.nasa.gov/30951 https://www.nasa.gov/mission_pages/WISE/multimedia/gallery/pia13119.html https://phys.org/news/2018-08-kepler-supernova-explosion-survivors-left.html https://www.universetoday.com/142734/hubble-has-a-brand-new-picture-of-the-massive-star-eta-carinae-itcould-detonate-as-a-supernova-any-day-now/ https://astronomynow.com/2018/08/03/astronomers-stunned-again-by-eta-carinae-the-star-that-will-notdie/ https://www.youtube.com/watch?v=cD0HshyLHdY [link broken] https://hubblesite.org/contents/media/videos/2018/33/1170-Video.html?keyword=Supernovae https://apod.nasa.gov/apod/ap190110.html http://blair.pha.jhu.edu/hstvela/hstvela.html http://earthsci.org/space/space/tektites/tektites.html http://www.jsg.utexas.edu/npl/outreach/tektites/ https://www.academia.edu/75124083/Dangers_to_Earth_from_Ancient_Supernovas Note that even broken links should be acknowledged if their temporary presence contained knowledge influential to the author’s conclusions. References: 1) Pilar Ruiz-Lapuente et al (2018) Tycho's supernova: the view from https://arxiv.org/abs/1807.03593 2) Pilar Ruiz-Lapuente et al (2018) No Surviving Companion in Kepler's Supernova, The Astrophysical Journal DOI: 10.3847/1538-4357/aac9c4 https://phys.org/news/201808-kepler-supernova-explosion-survivors-left.html 3) Vink, J. (2008) The Kinematics of Kepler's Supernova Remnant as revealed by Chandra https://arxiv.org/abs/0803.4011 4) A. Loeb, F.A. Rasio, J. Shaham (1993) Ejection of Fragments in Supernova Explosions, page 3; https://arxiv.org/abs/astro-ph/9405071 5) ibid, page 1 6) ibid, page 6 7) Colgate, SA (1971) The velocity and composition of supernova ejecta , page 74 https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720004110.pdf 8) Koeberl , C. (1994) Tektite origin by hypervelocity asteroidal or cometary impact: Target rocks, source craters, and mechanisms. in B.O. Dressler, R.A.F.Grieve, and V.L. Sharpton, eds., pp. 133–152, Large meteorite impacts and planetary evolution. Special Paper no. 293. Geological Society of America, Boulder, Colorado. https://www.univie.ac.at/geochemistry/koeberl/publikation_list/095-Tektite-origin-by-impact-GSA-SP2931994.pdf Tags: Ancient Astronomy, catastrophism, pole-shift, Chandler wobble, impact event, comet impact, Oumuamua, gravity wave, supernova ,remnant, stellar-merger This article is slightly reformatted from that published as an interactive webpage in 2019: https://www.academia.edu/75124083/Dangers_to_Earth_from_Ancient_Supernovas Citation: Dunbavin, Paul (2020) Dangers to Earth from Ancient Supernovas, in Prehistory Papers, pp 1-12, Third Millennium Publishing, Beverley, ISBN: 978-0-9525029-4-4 ************************************************ A second article follows below: Supernova Ejecta and the Dangers to Earth Paul Dunbavin (2022) Summary: As discussed in an earlier article ‘Dangers to Earth from Ancient Supernovas’ the risk of catastrophic collision with a comet or asteroid comes not just from objects orbiting our sun. There are other forces that may reach us from the galaxy or perhaps from the wider cosmos. While astronomers typically focus upon the objects that they can detect, optically or by any other method, the real danger may be from forces that we are unable to see or predict. In this article the focus should fall not on the stellar outbursts themselves rather upon their wider effects and the debris that they eject; and how these events could have caused catastrophic phenomena in Earth prehistory. It is not unreasonable to assume, given the advance of science and mensuration, that a day will arrive when astronomers can map every tiny asteroid and comet that orbits the sun, right out to the limits of the Oort cloud; and with the aid of supercomputers to predict their orbits far into the future. Those that might one day pose a threat could be watched and given a gentle ‘nudge’ to change their orbit and we may think ourselves safe again. The ‘Domesday comet’ is probably already on its way and will one day reach us. Perhaps in the meantime we may ponder how to divert it. But what about those visitors on a hyperbolic trajectory like Oumuamua and comet Borisov that originate from beyond our solar system? When I first wrote about extra-solar comets and oblique impacts in the early 1990s, the suggestion that comets might strike the Earth was still a toxic subject – until the impact of comet ShoemakerLevy-9 on Jupiter was witnessed on our TV screens. For most of the era of telescopic astronomy, keen amateur observers discovered solar asteroids and comets only when they passed close enough to be seen as tiny objects moving against the stellar background. There was what Stefan Michalowski called the ‘giggle factor’ attached to the possibility of impacts. [1] Eugene Shoemaker declared that the ‘giggle factor’ was gone when we witnessed a comet strike giant Jupiter. Sadly, denial has not gone away, because there remain other unseen dangers that could harm our planet or may have done so in the past. As astronomers probe the universe in new ways, they discover many new phenomena: quasars, pulsars, dark-matter halos, rogue planets, gamma-ray bursts, gravitational waves; all unheard of half a century ago. What next? Catastrophism in Earth history? Many enigmas and possible catastrophic episodes may be cited during human prehistory that demand an explanation as to what could have caused them. The confirmation that an asteroid strike in Yucatan caused the ancient demise of the dinosaurs has set the norm and any suggestion of catastrophic phenomena in more recent Earth history founders on the reply: where is the crater? Even the colossal asteroid impacts that cause mass extinctions would not have sufficient kinetic energy to appreciably affect the Earth’s axis or its orbit. This has long been sufficient for mainstream science to dismiss the idea of changes to Earth’s obliquity and pole shifts during recent prehistory as pseudo-science. This has now become a serious blind spot in our understanding of the past. Gradualist geology and climate science cannot explain the abrupt transitions between glacial periods, and at the end of the Ice Age; or the sharp transitions between stable climate regimes that have occurred during the Holocene. It cannot explain the rapid changes of sea level: the raised beaches and submerged forests that have transpired over the same period. It could not explain the references to astronomical phenomena described in various religious and mythological sources that suggest ancient pole shifts and axis tilts. Gradualist geology could not explain a possible change to the length of day since the earliest calendars. It could not explain climate and sea-level events, such as Joseph’s famine, or Atlantis – or Noah’s Flood. These examples from human prehistory demand a source of high-energy catastrophic events that do not leave an obvious impact crater. They were survivable events (i.e. they were not followed by a mass extinction) yet they possessed sufficient energy to have reset the rotation and climate of the Earth. Here are just a few suggestions based on the latest astronomy and physics. Hyperbolic Exocomets The appearance of comet Oumuamua passing close to us on its hyperbolic trajectory in 2017 has opened minds. Just two years later comet 2I/2019 Borisov was observed with an even higher excess velocity. With two such discoveries within just two years we have to wonder how many earlier examples could have been missed. [see note 1] Astronomers have long been aware of hyperbolic comets with a small excess velocity; but these could be explained as solar comets ejected by a close encounter with one of the planets, only to fall back millions of years later. [2] Oumuamua was a tiny object unnoticed until it was already on its way out of the solar system, most likely an asteroid ejected from its own star system. Its elongated shape (at most 1000 x 100 m) suggests that it is a fragment of a larger planetesimal torn-apart by whatever event projected it into interstellar space. Comet Borisov was somewhat larger and was enveloped in a coma more closely resembling a solar comet – apart from its excess velocity. Just recently (2022) I have noted the possibility of impacts by exocomets mentioned by one of the ‘television academics’, together with another guest who ventured the possibility of oblique ‘bouncing’ impacts that would leave little trace on the Earth’s surface. Such discussion could never have happened in earlier decades. When first I explored such matters in The Atlantis Researches back in the 1990s the concept of impact events was still derided as mere pseudo-science; one simply could not mention such things and be taken seriously. Supernovas and Remnants Astronomers regularly observe supernovas in distant galaxies although none have been observed in our own galaxy in the era of telescopic astronomy. An earlier article Dangers to Earth from Ancient Supernovas examined the question of what happens to the cloud of smaller bodies that must be orbiting a massive star before it goes nova. [3] These may comprise a range from planetesimal-sized objects down to meteorites small enough to hold in your hand. Pieces of the exploding star’s iron and silicon core might also be flung-out by the rapid spin-up of a supernova as it collapses. If these are propelled-away rapidly enough then their kinetic energy would exceed any threat from a solar asteroid. By the time the expanding shell of high-energy meteors reached us it would be so dispersed that they would be millions of kilometres apart. They should arrive with about the same regularity as we observe local supernovae (so about every few hundred years) with impacts being even less frequent. We should only detect such meteors during the brief few days when the shell of solid ejecta passes rapidly through the solar neighbourhood. Around every giant star there must be a region where planetesimals and asteroids orbit in a kind of perverse ‘Goldilocks zone’. The lifetime of a supergiant star is just a few million years; not long enough for planets to coalesce. Before it explodes the star must pass through an expansive Wolf-Rayet phase that would envelop the planetesimals in its gas cloud. Close-in to the final supernova explosion the asteroids would be reduced to dust to become part of the visible remnant, eventually to cool and merge with the interstellar medium. Further out, the expanding shock wave would pass by the asteroids leaving them battered but still in orbit about the collapsed star. Between these two extremes there must lie a zone where the planetesimals are disrupted yet are not reduced completely to dust; fragments of an optimal size would accelerated away by the wind of the supernova. Astronomers observe visible supernova remnants expanding at velocities of 1500 km/s (Crab Nebula) and even 13800 km/s (Cassiopeia A) Compare these to the relatively sedate orbital velocity of Halley’s Comet at 55 km/sec or even the unbound Oumuamua at 87.3 km/sec. One will often see, discussed in various astrophysical papers, the explanation that visible supernova remnants fade as they cool and expand until their density diminishes to that of the interstellar medium. This really amounts to a near-perfect vacuum colliding with an even more perfect vacuum a strange concept! The meteorites that regularly strike the Earth have orbited in the solar wind since the formation of the solar system and have not been halted. If a supernova remnant contains sweptup solid ejecta then, at the hyper-velocities considered, there is nothing in the interstellar medium that could prevent the shells of meteors from expanding long after the visible nebula has faded. Supernovae are not the only potential source of hypervelocity comets and asteroids that could reach the solar neighbourhood. Since the 1950s when Hoyle first proposed the theory of nuclear synthesis in stars the study of stellar collapse has been further refined. Physicists now recognise that even the high densities of a supernova core-collapse are insufficient to explain the abundance of the r- s- and p- process elements heavier than iron and nickel, such as gold, platinum and uranium. To form these heavy nuclei requires the high densities of a neutron star merger – themselves already collapsed supernova remnants. By inference, the presence of these heavy elements on Earth mandates that the primaeval solar nebula must have been preceded by a neutron-star merger. Gamma Ray Bursts Discovered accidentally in the 1960s by Vela satellites monitoring for nuclear tests, these were soon recognised as cosmic in origin, the product of explosions in distant galaxies. Two classes of gamma ray sources are now recognised: long bursts caused by implosion (hypernova) of high-mass luminous stars; and the short bursts attributed to the merger of neutron stars. Such collapses emit polar jets as the particles and radiation are channelled by the magnetic fields. The only reason we observe so many is that their magnitude is so bright that they are visible from the edge of the observable universe. Even then we only see that fraction whose jets are pointed directly towards us. Gamma ray bursts are statistically rare, loosely estimated at a few per million-years in any galaxy; but consider that there must be 180 times this estimate for events where the polar ‘beam’ is not pointed in our direction. Some theories require that the remnant left behind would be a magnetar – a fastspinning neutron star. Some theories even suggest that the Cambrian extinction some 488 million years ago was caused by a gamma ray burst in the solar neighbourhood. However, we need not dwell on the causal mechanism of such events (which is after-all only informed speculation by astrophysicists) rather to consider the solid ejecta and gravitational waves that they must release. FBOTs In 2018 astronomers discovered evidence in distant galaxies for a new class of supernova explosion. These have been termed Fast Blue Optical Transients (or FBOTs). Some have been given convenient nicknames; one explosion, known as “the Cow ”, was observed to be 10-times more powerful than any previously known supernova. [4] Another named “Koala” was almost as bright as a gamma-ray burst. [5] However, while gamma ray bursts may eject just a small mass of high-energy particles and radiation along the polar beams, the FBOTs may launch as much as 10% of our Sun’s mass at relativistic speeds approaching even the speed of light. Unlike a gamma-ray burst, the material ejected by an FBOT leaves the star in all directions. The name derives from the characteristic that the bright flash fades much more quickly than a normal supernova and they are hotter – the high temperature giving them their blue tint. Astronomers theorise that this new class of supernova needs a different mechanism to explain them. One suggestion is a black hole absorbing a white dwarf or a neutron star which then fades rapidly as the remnant falls within the event horizon; alternatively, they may be examples of a core collapse producing a black hole, but in this case the polar ‘beam’ of gamma rays is not pointed directly at us. The focus here has to be on the material expelled by the FBOT at relativistic speeds. Again, such ejecta must comprise small solid bodies, not just streams of hot gas. We may only speculate that the remnant, if we could observe one, would also fade more rapidly that any known remnant nebula. If such explosions can be observed in distant galaxies, then it follows that they must have occurred in the Milky Way galaxy and their nebulae have long ago dispersed and faded – but their shell of ejected meteors, travelling at relativistic speeds, continue to expand. If the supernova creates a central collapsar then its gravity may be enough to pull-back and retain much of the ejecta within the expanding remnant, but not when the parent star has been completely disrupted as in a Type I supernova. Ironically, the least powerful and most common class of supernova may present the greatest danger to us – and once the gaseous remnant has dispersed – totally undetectable by astronomers. Unnovas Another phenomenon related to the fast stars and FBOTs is the Unnova, sometimes misleadingly called a failed supernova. These are very far from failures; they are examples of the most massive stars (yellow hyper-giants of 20-60 solar masses) that try to explode by core-collapse but are too massive and are rotating relatively slowly, such that their light, or anything else, cannot escape from the event horizon. To our eyes the collapsing star would simply pop-out of existence. There are candidate stars that may be examples of this phenomenon; N6946-BH1 was observed to brighten and fade in 2009. The search for such stars has only come to the fore since the millennium as astronomers had been unable to find supernova remnants formed by the most massive supergiants. Once again, we should expect that meteors and comets in just the right orbit might be whipped around such a collapsing star and thus be accelerated into the galaxy at relativistic velocities. This is really no different from the way that hyperbolic solar comets are ejected from our own solar system by close passage to Jupiter or Saturn – except that the velocities are so much higher. We may have an example in one of our galactic neighbours: Cassiopeia A that exploded unnoticed in the mid-seventeenth century. Here astronomers observe not only the rapid expansion of the remnant at 21.6 million km/h, but also a region that is falling back at an equally impressive velocity of 6.9 million km/h; perhaps an indicator that it is under the intense gravitational pull of an invisible former companion star. [6] Consider for a moment how long it might take for supernova ejecta to reach us. To take again the example of Cassiopeia A; if an ejected meteor were travelling at the observed rate of expansion, then at its distance of 10,000 light years it should reach us about 220,000 years from now. The immediate danger would therefore come from a similar supernova that exploded at this distance two hundred and twenty thousand years ago and whose ejecta would only now be reaching us. Of course, the fast meteors and exocomets could approach from various distances and velocities; and from any direction. There is little or no prospect of predicting such arrivals until humans become capable of interstellar travel. Rogue Stars and Planets Other possibilities exist for sources of high-energy ejecta that could reach the earth. At the centre of our galaxy lies a supermassive black hole of 4 million solar masses called Sagittarius A-Star. We have all seen the excellent animations of the closest stars as they are observed to swing around it at velocities so fast that that they can be measured. In 2014 Sgr A* was observed to tear apart a gas cloud surrounding a small star. However, recent analysis would suggest that less than 1% of the matter orbiting the black hole actually falls within its event horizon; the rest is ejected into the galaxy. [7] In 2019 one such fast-star S5-HVs1 was observed to be leaving the galaxy at a velocity of 1700 km/sec. Its track indicates that it has survived a close encounter with Sagittarius A-star. Again we should ask: how many smaller unseen rogue planets, comets and meteors are passing by us at comparable velocities? Answer: there could be billions. No longer is it mere science fiction. Tektites Should one of the hypervelocity fragments from an ancient supernova strike the Earth then what kind of physical evidence might we expect it to leave behind? Certainly not a crater, any more than you would expect a bullet from a gun to leave a crater in soft material. However the science of bolide ballistics does give us useful analogies. Most likely they would drill a hole deep into the mantle before being dissolved, or perhaps a ricochet scar from an oblique impact. The most likely hard evidence would be a strewn field of micro-tektites (impact glass) around the point of entry. We are considering here a football-sized body, or even smaller, travelling so fast that that they could penetrate to the mantle. We should expect the impact site to be inconspicuous and disguised by infill or volcanic extrusions. [8] Tektite Strewn Fields. Most of the largest are millions of years old are linked to ancient craters. Examples of Holocene age are likely to be microtektite sites, too small to show on a large-scale map. Prime locations to search for hard evidence would be the smallest tektite fields that are not associated with any known crater; and always bear in mind that three-quarters of all impacts must occur in the ocean leaving even less accessible evidence. It may be easier to find one on the Moon, where there has been less geology to conceal them. We shall see. Very little physical evidence would remain on the Earth’s surface after a few hundred years but we may still detect short-lived radioactive isotopes that were synthesised in the parent supernova. New Physics If you wish then you can look into the more speculative and exotic phenomena that astronomers and physicists now consider possible. Gravitational Waves Long theorised but first detected in 2015, these are thought to be produced by the mergers of massive objects such as neutron stars and black holes. They must also occur when stars fall into Sagittarius Astar and when galaxies and supermassive black holes merge: a frightful concept! All the events so-far detected by the most sensitive gravitational wave detectors on earth result from mergers of collapsed stars in distant galaxies. Typically the amplitude of the waves is less than the width of a human hair and would go unnoticed – each of us has probably experienced numerous gravitational waves during our lifetime; it is no different to the radio waves and neutrinos that pass through us all the time. A gravitational wave is a stretching and squeezing of the space-time fabric produced by high gravity events. Atoms and particles, as well as planets (which are merely large groups of atoms for this example) would alternately stretch and squeeze according to the wavelength. It is important to visualise that it is the spacetime structure that deforms not the matter that occupies it. Precisely what we would feel from a gravitational wave that originated much closer to us could only be speculation and imagination at this point. Whatever else, the gravitational wave has a point of origin and a direction. It carries energy and it should affect the Earth in the same way as any other impulse. It would act to change the angular momentum of the planet, resulting in a nutation of the axis and could even alter the length of day. A change to the shape of the Earth (the squeezing and pulling) must also trigger a wobble and a pole shift. The real difference however, between this and the impulse delivered by an impact event, is that it should leave no crater or any other hard evidence on the surface. A gravitational wave would not have to be spectacular to cause geological effects; a variation of perhaps a few millimetres might be enough to trigger worldwide earthquakes and flows of magma in the core and mantle, thus altering the shape of the geoid and its rotational balance. The rest is then just known geophysics. Once again, it is important to appreciate that although physicists may talk as if they know what is going-on, they don’t! No-one really understands gravity! Mini-black-holes The only known process by which a black hole could be created is by the gravitational collapse of a massive star at the end of its life, such that the core falls within its event horizon and the required escape velocity exceeds the speed of light. To form a stellar black hole, the collapsed core must be of a minimum of about 2 solar masses, commencing as a supergiant of 25+ solar masses, The resultant black hole would occupy a diameter of about 25 km. However, there is no minimum size limit so long as the required density could be achieved. Scientists such as Jakub Scholtz and James Unwin propose that in the extreme conditions of the early universe, local unevenness could have created conditions where matter was clumped sufficiently for mini black holes to form. They suggest that the as yet unobserved Planet 9 could be a primordial black hole about the diameter of a tennis ball. [9] Some primordial black holes might be no bigger than fundamental particles. Once in existence, these would behave like any other massive object subject to gravity as the universe expanded; most falling into supermassive black holes and stars or orbiting them. This raises the obvious question why are there not one or two orbiting the sun; are they the missing ‘dark matter’, etc. Popular science-fiction would give us the notion that we would be sucked into such a black hole, but this is erroneous; from distance they would represent no more danger than a rock of similar mass. However, there is always the possibility that a close fly-by could produce tidal effects in the oceans and crust; and resultant catastrophism as has been proposed by other authors. The mini-black-hole theory is not one that that I favour but is listed here for completeness. Gravity Leaks? What is gravity? If you know then please tell the physicists. Modern astrophysicists can tell you how it behaves, building upon Einstein’s relativity; they can even suggest that the newly-confirmed Higgs Boson confers mass; and it is the mass (whatever that is) that bends the space-time fabric; but this merely transfers the problem to a deeper level of unknown. A stellar cast of physicists at LIGO sought to use gravitational waves as a way to probe whether gravity was ‘leaking’ from our universe into an adjacent parallel universe. They seem to be convinced that it does not; but what about gravity leaking into our universe from an adjacent one? This conundrum derives from the multiverse theory, whereby an infinite series of parallel universes or ‘branes’ must exist in parallel, splitting-off at quantum level. These other universes would be ‘stacked’ adjacent to our own in a fourth dimension, each a Planck distance apart – rather like twodimensional sheets of paper stacked in the third dimension. Gravity obeys an inverse square law; that is to say, it’s strength is inversely proportional to the square of the distance from the source. Therefore it is reasonable to suggest that its influence in the higher dimensions would obey the same law. The gravity that we experience is therefore just a fraction of the total force, which could explain why it is so weak compared to the other fundamental forces. This raises the possibility that the Earth may pass close to a source of mass (a planet or star) lying in an ‘adjacent’ universe and if it be close enough then its gravity would be felt in our own. These are the science fiction ‘gravity anomalies’ that you may see on an episode of Star Trek – gravitational pull emanating apparently from nowhere! Indeed it is such a difficult concept that there is not even adequate language to describe it. All we really need to consider is that the gravitational effect of a mass in an adjacent universe should be similar to gravity from a mass in our own universe. However, such physics as is published would suggest that the body must approach extremely close – almost passing through us – in the higher dimension in order for us to experience its effects. Perhaps we should not worry about this idea until a physicist can explain what dark matter is and where it is. Conclusions If we observe exocomets then there must also be many smaller exo-meteors. If we can watch highenergy phenomena occurring in distant galaxies then they must also occur in our own galaxy. Because we only see the rare phenomena during our short human timeframe we fail to perceive the long-term threat that they pose. It is rather like building your house close to a volcano and relying on the security that it has never erupted in your lifetime. We cannot do much about the future, but we can at least recognise the effect they might have had in the past and consider their effect on recent geology and human prehistory. It is unfortunate that so much discussion of catastrophism in prehistory during the twentieth century was so unempirical that it could be easily demolished by scientists. This has led to a neglect and unwillingness by mainstream geologists to consider the question for fear of professional ridicule. It is a subject that must be considered. All of the phenomena suggested above could cause cataclysmic episodes on the Earth and yet they would not leave any hard evidence on the surface. Let me pose you a troubling series of questions. How do you know that there is not a dark collapsar lurking, a few thousand light-years from earth, that ‘exploded’ millennia ago and sent a shell of meteors in our direction at unthinkable velocity? Is there a dark star awaiting discovery in our galactic locality, of just the right mass that may collapse further and send a gravitational wave in our direction disturbing our stable rotation as it passes through us? What would that feel like and what might its geological effects be? Is there a planet in an adjacent parallel universe that may pass close-enough in a higher dimension for its gravity to leak into our own? Are you waiting for a recognised ‘expert’ or professor to tell you whether such concepts are real or pseudo-science? Another definition of pseudoscience might be science that your expert has not yet thought of, or perhaps fears to mention lest their papers be rejected. Beware the giggle factor! Note 1: As this article was in preparation, evidence was released that a 0.45m diameter meteor estimated to be travelling at 210,000 km/h (58.33 km/sec) broke apart in the atmosphere over New Guinea in 2014. This discovery actually predated Oumuamua but was awaiting conclusive verification of the data. As may be noted from the above discussion this velocity is still far below the maximum that could be generated by stellar phenomena, but well above the commonly observed velocities for meteorites of solar system origin. The authors suggest that the bolide came from the inner part of a planetary system in the disk of the Milky Way galaxy. [10] Note 2: Again as this article was in preparation, evidence was published that a bolide discovered in Egypt in 1996 known as the Hypatia stone was probably an ancient meteorite of non-solar-system origin. The composition was so unusual that the researchers suggest it was most likely produced in a Type 1a supernova. The conservative research suggests that it formed in a region of interstellar dust within the proto-solar nebula, which preserved its origin, rather than suggesting that it formed around another star. [11] Alternatively, it could be evidence that not all meteors ejected from supernovas will be travelling at hypervelocity. Relevant Hyperlinks https://solarsystem.nasa.gov/asteroids-comets-and-meteors/comets/2I-Borisov/in-depth/ https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1991JBAA..101..119H&defaultprint=YES&filetype=.pdf https://arxiv.org/abs/2201.08911 https://www.thoughtco.com/eye-of-the-sahara-4164093 https://astrobites.org/2011/10/24/the-case-of-the-disappearing-star-un-novae-and-ultra-long-gamma-ray-transients/ https://en.wikipedia.org/wiki/N6946-BH1#/media/File:PIA21467.jpg https://en.wikipedia.org/wiki/Failed_supernova https://hubblesite.org/contents/media/images/2017/19/4039-Image.html?news=true https://www.nasa.gov/mission_pages/chandra/multimedia/black-hole-SagittariusA.html https://en.wikipedia.org/wiki/File:SgrA2018.gif https://www.universeguide.com/fact/hypervelocitystars http://www.sci-news.com/astronomy/s5-hvs1-hypervelocity-star-07799.html https://geologyscience.com/gallery/eye-of-the-sahara-or-richat-structure/ https://www.scientificamerican.com/gallery/the-smallest-known-black-hole/ https://arxiv.org/abs/1811.00364 https://www.forbes.com/sites/startswithabang/2019/03/15/this-is-why-the-multiverse-must-exist/?sh=15cca9566d08 https://public.nrao.edu/gallery/category/supernova-explosions-and-supernova-remnants/ https://www.space.com/38471-gravitational-waves-neutron-star-crashes-discovery-explained.html https://www.sciencedirect.com/science/article/pii/S0016703718301236 https://public.nrao.edu/gallery/category/supernova-explosions-and-supernova-remnants/ https://ntrs.nasa.gov/api/citations/19980007188/downloads/19980007188.pdf https://www.iac.es/en/outreach/news/astronomers-discover-first-supernova-explosion-wolf-rayet-star https://www.msn.com/en-gb/news/techandscience/this-tiny-space-rock-might-be-the-1st-physical-evidence-of-araresupernova/ar-AAXx692?ocid=msedgntp&cvid=c0c26c401fce47ecb84ab52edc4b1d1a https://www.academia.edu/75124083/Dangers_to_Earth_from_Ancient_Supernovas References 1 'Giggle factor' is no laughing matter to scientists, Posted 3/11/2003 8:53 PM, by Eric J. Lyman, Special for USA TODAY. 2 Hughes, D.W. (1991) On Hyperbolic Comets, J. Br. Astron. Soc. 101, 2, 1991 3 Dunbavin, Paul (2020) Dangers to Earth from Ancient Supernovas, in Prehistory Papers, pp 1-12, Third Millennium Publishing, Beverley, ISBN: 978-0-9525029-4-4 4 Swift spectra of AT2018cow: A White Dwarf Tidal Disruption Event? https://arxiv.org/abs/1808.08492 5 Ho, Anna Y. Q. et al (2020) The Koala: A Fast Blue Optical Transient with Luminous Radio Emission from a Starburst Dwarf Galaxy at<i>z</i>= 0.27, The Astrophysical Journal, 859, 1 https://iopscience.iop.org/article/10.3847/1538-4357/ab8bcf 6 Vink, J. et al (2022) The forward and reverse shock dynamics of Cassiopeia A https://arxiv.org/abs/2201.08911 7 Wang, Q.D. et al (2013) Dissecting X-ray-emitting Gas around the Center of our Galaxy, arXiv:1307.5845 [astro-ph.HE] or arXiv:1307.5845v2 [astro-ph.HE] https://doi.org/10.48550/arXiv.1307.5845Rogue stars (Wang?) https://arxiv.org/pdf/1307.5845.pdf 8 Petersen, Carolyn Collins. "What Is the Eye of the Sahara?" ThoughtCo, Aug. 27, 2020, thoughtco.com/eyeof-the-sahara-4164093. 9 Scholz, Jakob and Unwin, James (2019). What if Planet 9 is a primordial Black Hole? https://arxiv.org/pdf/1909.11090.pdf 10 Amir Siraj, Abraham Loeb, The 2019 Discovery of a Meteor of Interstellar Origin https://arxiv.org/abs/1904.07224 11 Jan D. Kramers, Georgy A. Belyanin, Wojciech J. Przybyłowicz, Hartmut Winkler, Marco A.G. Andreoli, The chemistry of the extraterrestrial carbonaceous stone “Hypatia”: A perspective on dust heterogeneity in interstellar space, Icarus, 382, 2022, 115043, ISSN 0019-1035 https://doi.org/10.1016/j.icarus.2022.115043 https://www.sciencedirect.com/science/article/pii/S0019103522001555 Tags: Ancient Astronomy, catastrophism, pole-shift, Chandler wobble, impact event, comet impact, Oumuamua, gravitational wave, supernova, supernova remnant, stellar-merger This is a format-adapted version of that originally published in 2022 as an interactive webpage . Citation: Dunbavin, Paul (2022) Supernova Ejecta and the Dangers to Earth, in Prehistory Papers II, pp 1-17, Third Millennium Publishing, Beverley, ISBN: 978-0-9525029-5-1 

Dangers to Earth from Ancient Supernovas and Supernova Ejecta and the Dangers to Earth Introduction The following combines two articles that were originally published as webpages to illustrate the possible source of high-energy phenomena from space that would have the potential to change the Earth’s rotation axis – yet without leaving any physical scar on the surface. The articles are not primarily written for astronomers (although I hope they would find the discussion of interest) but for the interest of the general reader and the catastrophist researcher. The articles build on the concepts touched-upon in my 2006 book: Under Ancient Skies. [1] I hope that the discussion here will give some answer to those nineteenth-century academics who declared that pole-shifts and axis-tilts cannot happen; negative pronouncements that even today hold back discussion by modern science. The first article concentrates primarily upon the dangers posed by fast supernova ejecta, while the second also briefly explores other high-energy phenomena recently discovered by astronomers. Thanks to new space-based telescopes, the discoveries are coming so fast that they appear in publication faster than one can write about them. The possibility and likelihood of pole shifts or changes to the Earth’s obliquity (axis tilts) were advanced by various enthusiasts during the twentieth century, principally following the dubious astronomy of Ivan Velikovsky or the ‘crustal slippage’ ideas of Charles Hapgood – or even Dodwell’s unpublished proof of the Bible. All of these were based on 1950’s science predating many of the scientific advances in geology and astronomy from the 1960s onwards, yet they continue to appear in ‘popular’ science books up to the present day. Many of these modern authors fail to appreciate that a pole shift and an axis tilt are not the same thing at all and have quite different causes. At the base of scientific scepticism lie the pronouncements of eminent nineteenth century and early twentieth century physicists. Note as a typical example the remarks made in 1876 by Sir John Evans; the eminent Professor Twisden; and (below) the Reverend Hill, then a physics tutor at Cambridge: Internal changes cannot alter the axis, only the distribution and the motion of matter about it. If the mass began to revolve about a new axis, every particle would begin to move in a new direction. What is there to cause this? When a cannon ball strikes a metal plate obliquely, the shock may deflect it into a new direction. The Earth’s equator is moving faster than a cannon ball. Where is the force that could deflect every portion of it and every portion of the Earth into new directions of motion? [2] Also since the 1960s the study of the Earth’s free wobble modes: the Chandler wobble and the Core wobble have advanced to a point where we may see more clearly the forces that are needed to trigger them. The Chandler wobble is observed to cause small pole shifts and is triggered by internal changes in the mass distribution of the planet; The Core wobble requires a substantial external force from space to excite it but it could trigger a change of the obliquity. We therefore need to investigate what those forces from the wider cosmos might be. 1 Dunbavin, Paul (2006) Under Ancient Skies, Ancient Astronomy and terrestrial Catastrophism, Third Millennium, Nottingham ISBN: 0-9525029-2-5 2 Evans, J. Quart. Journ. Geol. Soc. 1876, xxxxii, proc., p108 (and later responses) Dangers to Earth from Ancient Supernovas Paul Dunbavin (2019) Summary: This article is less about supernovas and star-mergers themselves, rather the possibility of fast-ejecta from them impacting the Earth. For the benefit of the general reader scientific terms are kept to a minimum and explained where necessary or may be pursued in the suggested links. Astrophysical research papers are not usually written for the benefit of the general reader or even for the cross-disciplinary researcher, but for their specialist colleagues. It should not therefore be assumed that the present author fails to understand the terminology and equations in the cited sources; but neither should it be assumed that he understands all of them! In proposing a theory that the Earth’s axis has changed in recent prehistory – be it either a pole-shift or a more extensive change to the obliquity or length-of-day – requires a mechanism to explain how it could happen; the question cannot be ducked. Even a giant asteroid impact like that which caused the extinction of the dinosaurs would not possess enough energy to significantly disturb the Earth’s axis and rotation. This has long been sufficient cause for geologists and physicists to dismiss the entire subject of pole shifts and axis-tilts as pseudo-science. The historiography of this subject was discussed in my book Under Ancient Skies. It is true; there have been many naïve pole-shift theories which do not acknowledge the vast energy that would be required. Yet there are clues that something did disturb the Earth’s rotation at the close of the ice-age and also again in the mid-Holocene (see: Raised Beaches and Submerged Forests - Curious Anomalies) To propose a theory of changes to the axis requires an external force that could significantly alter the Earth’s angular momentum yet without leaving an obvious impact scar; and without causing a mass extinction event. As discussed in Under Ancient Skies there are three principal candidates that might offer an answer to this conundrum: 1) Small-fast meteors ejected by ancient supernovae, stellar mergers and active galaxies. 2) Gravity waves from mergers of compact stars in the close solar neighbourhood 3) As yet unknown physics: dark-matter; gravity leaking from parallel universes, etc. Here we shall discuss only the first possibility. Since the 1990s there has been much discussion of the collision dangers from near-earth asteroids that we could detect. These might destroy cities and create dust-veils but would not possess enough energy to significantly change the axis of rotation. Comets could strike with higher velocities up to 72 km/sec for a head-on collision – but while calamitous for all life, even this would not be enough to make the world wobble on its axis. Fast hyperbolic asteroids like Oumuamua that may have been ejected from other solar systems may travel even faster, but they still do not possess enough energy. Kinetic energy increases with mass, but with the square of the velocity (E=1/2mv2) and so the real danger comes from small fast objects potentially ejected by ancient supernovas. To experiment with the scale of this you may like to try-out this useful calculator tool: A little experimentation will show that the velocity of the comet would need to be travelling at a significant fraction of the speed of light to approach the kinetic energy of the Earth’s rotation, calculated at 2.138x1029 joules. Could a supernova or a stellar-merger send objects of such relativistic velocities in our direction? Might they reach us from even more distant active galaxies? The origin of the charged particles in cosmic-rays from such events is generally accepted, but the possibility of more substantial pieces of high-energy matter is more speculative. See for example this example from a 2014 discovery. Astronomers identify two classes of stars that explode as supernovae. The first is ‘core collapse’ (types II, 1b and 1c); these are massive stars that leave a compact remnant of some kind, a pulsar or a black hole. Typical examples of this type would be the Crab Nebula in the constellation Taurus and its central pulsar; or SN1987A which exploded in the Large Magellanic Cloud in 1987; the most recent that has been observed in our Galactic neighbourhood. The Crab pulsar is observed to rotate 33 times per second, and the surrounding nebula is expanding at about 1500 km/s. Another example would be Cassiopeia A, a strong X-ray source, which should have been first-visible from Earth around 340 years ago but went unrecorded. The remnant is seen to be expanding away from a central pulsar at: “up to 31 million miles per hour [13800 km/s] (fast enough to travel from Earth to the Moon in 30 seconds!)”. For more information about Cassiopeia A, see this example from a NASA website which includes a Hubble photo. The second class of supernova is a ‘thermonuclear explosion’ (type 1a); less powerful but likely to be more common. We may compare these to a vast nuclear bomb. They are believed to be white dwarf stars that have accreted a shell of matter, usually pulled from a close companion star. When they reach maximum size (Chandrasekhar limit) they must contract further to a neutron star but this can cause a thermonuclear runaway that completely disrupts the progenitor star. They leave no central remnant behind and by definition they should all be of a similar energy. Tycho’s supernova SN1572 is one example, whose visible remnant has been variously calculated to be expanding asymmetrically at between 5,000 and 9,000 km/sec. [1] Another instance of this type of explosion within a close-binary system may be Kepler’s supernova of 1604, but its cause remains uncertain – a possible merger of two white dwarfs. SN1604 is described by astronomers as having been ‘unusually powerful’.[2] However, the estimated rate of expansion is comparatively low at 4200 km/s [3]. The recently discovered SNIa G1.9 + 03 may be another example of this type. Astronomers observe that stars don’t just explode without warning. Massive stars approaching their crisis will be surrounded by a dense planetary nebula ejected by novae in the later phases of their evolution. Within and beyond this will be the cloud of planetesimals, asteroids, meteors and comets that have circled the star ever-since it formed, equivalent to the Oort cloud around our Sun. These bodies are too small be detected but we know they must be present. Consider how many billions of icy comets and small asteroids orbit our own sun, completely unseen until one of them streaks through the sky as a comet. A prime example of an ‘overdue’ supernova is the star Eta Carinae, which survived a nova explosion observed in 1843 (a supernova ‘imposter’). The ejected matter is seen to be travelling at 32 million kilometres per hour! Astronomers cannot explain how the central star survived the nova as it is burning heavy elements in its core, its hydrogen fuel – long gone. It makes a startling image in the Hubble photographs. Fascinating as these spectacular examples are, it is probably the closer and less spectacular supernova remnants, those we can no longer see, which offer the more likely danger to us on Earth. The final collapse of a massive star occurs within a fraction of a second as it exhausts its silicon and lighter elements and has only iron remaining in its core. This cannot release further energy from nucleosynthesis to support itself and can only collapse down to incredible density as the iron is crushed to a rapidly-spinning ball of neutrons – a neutron-star. You may wonder how a collapse can cause an explosion. Various mechanisms are proposed and need not be discussed in detail here as we are more concerned with the remnant rather than the explosion. Most often discussed is that the collapsing matter ‘rebounds’ from the dense nucleus and collides with the in-falling matter triggering nuclear synthesis; and that the resulting burst of radiation and neutrinos would blow away the shell of the star. However another theory considers that the principle mechanism could be the rapid spinning-up of the core as it forms the central pulsar or black-hole; this throws-out the neutron-rich matter and the collapsing shell, in what is sometimes termed a ‘sausage instability’ (mass-shedding via outgoing spiral arms of matter). [4] Remember this all occurs within a fraction of a second! A naive illustration would be to swing a string of sausages round your head – it is the fast-moving outer links that are most likely to fly-off at a tangent! These ejecta collide with the in-falling stellar envelope and triggers further synthesis of heavy elements and vast release of radiation that we observe. The energy is carried away in a shock-wave that sweeps up everything surrounding the star and creates the visible nebula. The expansion of the ejected remnant then proceeds as the supernova fades. We may propose that when the shocked ejecta reaches the outer shell of meteors, asteroids and icycomets surrounding the exploding star then these would be disrupted into smaller fragments. Usually astronomers consider total disruption to gas and dust; and that the expansion ceases when the mass of the surrounding shell equals that of the unshocked interstellar medium. This may be so for most of the mass. However, bodies of optimum size and distance from the explosion may not be disrupted completely. If the explosion has enough energy to disrupt an asteroid then it must also be sufficient to propel away the fragments. Much depends upon how fast the collapsar is spinning. There is nothing in the interstellar vacuum of space that could then impede this shell of ejected meteors from expanding to infinity unless they encounter the gravity of another massive body (i.e. a star or planet). [A crude analogy for the non-astrophysicist: consider your garden blower as it easily blows-away the sand and leaves; the blower is strong and the leaves are light. However, if someone throws a pebble at you could you deflect it away with your leaf-blower? I don’t think so! How strong would your blower need to be; and how small must be the projectile for the blower to have any effect? How hard would you need to blow to completely disrupt the pebble?] A further source of fast ejecta from a supernova may originate from neutron-matter expelled from the dense core as it spins-up. Astronomers theorise that such matter should very rapidly decompress to heavy nuclei (r-process elements) and iron. Again, these are likely to clump rather than persist as dust and gas. Sometimes trails can be observed within supernova remnants, which are interpreted as fragments from the core travelling through the gaseous remnant. For each of these there must be many smaller unobservable clumps. What is to impede these ejected pseudo-comets from escaping to great distances? A complex collection of supernova remnants of various ages are found in the Vela nebula, revealed in a striking composite picture released by NASA. You may also like to read the interesting study of the vela complex by Bill Blair. If we take as an example the paper by Loeb-et-al; the authors consider the V-shaped wakes observed within the Vela supernova remnant that are loosely estimated to be moving away at around 3000 km/s. [5] They demonstrate that these could not be the ejected former planets of the parent star, as these should be totally disrupted and would long-since have faded from view. At the point where the fragments cease to be observable, the professional astronomers lose interest; the planetary fragments are assumed to vanish into the supernova remnant. The disrupted planetary fragments, travelling at even a fraction of the remnant’s expansion velocity, are still very fast compared to solar comets. Rather, the authors consider that the observed high-velocity fragments are more likely to have been formed in the dense core and then ejected as the central remnant spins-up (an asymmetric gravitational collapse). The neutronic matter re-forms into heavy nuclei, principally iron and nickel – but unlike a solar iron meteorite these should also contain short-lived isotopes of heavy elements and iron-60. The authors consider that there must be “many more, smaller fragments” that we cannot detect. [6] Again the professional astronomer seems to lose interest if the bodies are too small to be detectable with telescopes. In fact, the diffuse shell must continue to expand long after the remnant has faded and they will one-day reach us. How many other expanding shells of older supernovas are out there, whose nebulae have faded from view? Their ‘comets’ are still on their way towards us or have already passed through the solar system. Until quite recently, astrophysicists believed that all the elements heavier than iron were created in supernova explosions. However, it is now accepted that even the high density of a supernova corecollapse is not dense enough for the r-process to create these elements. To produce these requires the merger of two neutron-stars, or perhaps a neutron star and a white dwarf. These events generate intense magnetic fields that fling jets of matter away from both poles of the collapsing star at nearrelativistic speeds. These are also now believed to be the source of the gamma-ray bursts observed in distant galaxies; the bursts that are detected come from chance events where the polar jets are pointed directly at us. It is reasonable to expect that iron-rich meteor fragments might also be accelerated away by these intense magnetic fields. The next problem to consider is how often we may expect to encounter the diffuse shells of fastmoving meteors and comets; and how may we observe them in order to prove their existence? In our historical records, visible supernovae have occurred about ever 300-500 years on average, the most recent being that observed by Kepler in 1604. In all, there should be about two events per century for the Milky Way galaxy, which would give the above average for our observable region. [7] Events on the far side of the galaxy should represent no danger to us. Therefore, the expanding shells of ancient ejecta should arrive at the solar system with a similar regularity to the observed supernova events. Between these episodes we are unlikely to encounter supernova ejecta and it may be that no such encounter has occurred since the advent of telescopic astronomy. In most events, they may be expected to rapidly pass through the solar system without hitting a planet. Therefore we may postulate a collision-event perhaps every few thousand years; really energetic axis-tilting events should be even less common by a multiple of 180. Without precise observational data to cite, the speculation flag will inevitably be raised! When astronomers and popular commentators discuss the dangers from supernovas they tend to seek those that may explode within say, 500 light-years – the solar neighbourhood, such as the bright star Betelgeuse in Orion. The popular view is that as long as the supernova is more than say, 50 light-years away then we should be safe. The focus falls upon the gamma-ray burst or the intense flash of cosmic radiation and neutrinos that might reach us at the same time as we see its light; some others may consider the ‘bubble’ of charged particles, travelling typically at a fraction of light-speed that should reach us a few hundred years later. By contrast, many thousands of years may pass for the hypervelocity solid ejecta to reach us from stellar explosions. However, we may get some advance warning. The charged particles from the supernova, travelling at a fraction of the speed of light, should reach us well in advance of the solid bodies; we should therefore observe a change in the background cosmic ray flux. Perhaps astronomers could then calculate their point of origin and predict when the dangerous ‘comets’ will arrive. Then what should we do? A flux of small-fast-comets arrives at the Earth. This illustration was figure 10.1 of Under Ancient Skies We should also consider what the impact of a small-fast meteor on the Earth might look like; take as an example, a football-sized icycomet, perhaps with a solid core, travelling at the ejected supernova velocities discussed above. The composition is irrelevant, ice would be just as destructive as iron; it is the velocity that supplies the kinetic energy not the mass. There is no ideal research to cite here as such impacts have not been much considered by specialists. The best one can suggest is that it would drill deep into the crust, more like a bullet-hole than an impact crater. The impact would throw-out a tail of terrestrial rock far exceeding the small mass of the projectile, which would then dissolve deep within the earth. The best research we can consider would be the various theories for the formation of tektites, where we find strewn fields of these tiny impact-ejecta that are considered to be shocked glass formed from melted sedimentary rock as it re-enters the atmosphere. [8] Other than the tektites very little evidence would remain after a few thousand years; no crater, no tell-tale layer of Iridium, no evidence of a dust veil. We might however expect to find traces of heavy elements, and rare radioactive isotopes around the impact site – if we could find one! The consensus seems to be that very special and seldom-encountered high-energy events are required to explain the composition of tektites. For further information, the reader may like to pursue the following links: a basic introduction plus a more scholarly article: Conclusions A high energy impact event has the capacity to supply an impulse of kinetic energy in the direction of its travel. Depending upon the size, direction and velocity, this has the capacity to change the Earth’s angular momentum; and to excite the Chandler Wobble. Without ‘hard’ evidence then all we should expect to see in the geological record of the recent-past is evidence of the transient wobble and a pole shift; perhaps: a change of obliquity and a glitch in the length of the day. We might expect these effects to be of the order of arc-seconds or arc-minutes at most, but enough to be noticeable. This would manifest as sea-level and climate oscillations in the recent geological record; and in transitions from one stable regime to another. However, it must be stressed again that in order to change the Earth’s angular momentum by any significant amount, say, measured in full degrees or arc-minutes of latitude, then the impactor must arrive at a very high velocity perhaps approaching half the speed of light; and it would also have to be very small were it not also to cause a mass extinction event. To create impactors of such high energy we may therefore narrow down the source to those smaller chunks of heavy elements and iron ejected from the core of a supernova or star-merger event during its collapse. The only other source powerful enough might be the relativistic jets ejected from the poles of the collapsar during its rapid contraction phase; and one would have to be pointing in our direction from an ancient event. If it were closer then we could not escape the even more destructive effects of the gamma-rays! If something like this did reach us during Earth’s recent prehistory then astronomers should one-day be able to identify a candidate progenitor star, which should by now be detectable as a black-hole. Unfortunately, evidence of sea level and climate oscillations in recent prehistory can also be explained by other causes; and so without a clear worldwide pattern the sceptical geologists and climate specialists will not be convinced of catastrophic events from space. Astrophysicists are more openminded; they are accustomed to discussing hypothetical phenomena that they can’t touch; but geologists: they study rocks and they drill holes; it can be difficult to persuade them to look upwards. Relevant Hyperlinks https://www.calculatorsoup.com/calculators/physics/kinetic.php https://www.sciencemag.org/news/2014/07/physicists-spot-potential-source-oh-my-god-particles https://svs.gsfc.nasa.gov/30951 https://www.nasa.gov/mission_pages/WISE/multimedia/gallery/pia13119.html https://phys.org/news/2018-08-kepler-supernova-explosion-survivors-left.html https://www.universetoday.com/142734/hubble-has-a-brand-new-picture-of-the-massive-star-eta-carinae-itcould-detonate-as-a-supernova-any-day-now/ https://astronomynow.com/2018/08/03/astronomers-stunned-again-by-eta-carinae-the-star-that-will-notdie/ https://www.youtube.com/watch?v=cD0HshyLHdY [link broken] https://hubblesite.org/contents/media/videos/2018/33/1170-Video.html?keyword=Supernovae https://apod.nasa.gov/apod/ap190110.html http://blair.pha.jhu.edu/hstvela/hstvela.html http://earthsci.org/space/space/tektites/tektites.html http://www.jsg.utexas.edu/npl/outreach/tektites/ https://www.third-millennium.co.uk/under-ancient-skies Note that even broken links should be acknowledged if their temporary presence contained knowledge influential to the author’s conclusions. References: 1) Pilar Ruiz-Lapuente et al (2018) Tycho's supernova: the view from https://arxiv.org/abs/1807.03593 2) Pilar Ruiz-Lapuente et al (2018) No Surviving Companion in Kepler's Supernova, The Astrophysical Journal DOI: 10.3847/1538-4357/aac9c4 https://phys.org/news/201808-kepler-supernova-explosion-survivors-left.html 3) Vink, J. (2008) The Kinematics of Kepler's Supernova Remnant as revealed by Chandra https://arxiv.org/abs/0803.4011 4) A. Loeb, F.A. Rasio, J. Shaham (1993) Ejection of Fragments in Supernova Explosions, page 3; https://arxiv.org/abs/astro-ph/9405071 5) ibid, page 1 6) ibid, page 6 7) Colgate, SA (1971) The velocity and composition of supernova ejecta , page 74 https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720004110.pdf 8) Koeberl , C. (1994) Tektite origin by hypervelocity asteroidal or cometary impact: Target rocks, source craters, and mechanisms. in B.O. Dressler, R.A.F.Grieve, and V.L. Sharpton, eds., pp. 133–152, Large meteorite impacts and planetary evolution. Special Paper no. 293. Geological Society of America, Boulder, Colorado. https://www.univie.ac.at/geochemistry/koeberl/publikation_list/095-Tektite-origin-by-impact-GSA-SP2931994.pdf Tags: Ancient Astronomy, catastrophism, pole-shift, Chandler wobble, impact event, comet impact, Oumuamua, gravity wave, supernova ,remnant, stellar-merger This article is slightly reformatted from that published in 2019 as an interactive webpage at: https://www.third-millennium.co.uk/dangers-from-ancient-supernovas Citation: Dunbavin, Paul (2020) Dangers to Earth from Ancient Supernovas, in Prehistory Papers, pp 1-12, Third Millennium Publishing, Beverley, ISBN: 978-0-9525029-4-4 ************************************************ A second article follows below: Supernova Ejecta and the Dangers to Earth Paul Dunbavin (2022) Summary: As discussed in an earlier article ‘Dangers to Earth from Ancient Supernovas’ the risk of catastrophic collision with a comet or asteroid comes not just from objects orbiting our sun. There are other forces that may reach us from the galaxy or perhaps from the wider cosmos. While astronomers typically focus upon the objects that they can detect, optically or by any other method, the real danger may be from forces that we are unable to see or predict. In this article the focus should fall not on the stellar outbursts themselves rather upon their wider effects and the debris that they eject; and how these events could have caused catastrophic phenomena in Earth prehistory. It is not unreasonable to assume, given the advance of science and mensuration, that a day will arrive when astronomers can map every tiny asteroid and comet that orbits the sun, right out to the limits of the Oort cloud; and with the aid of supercomputers to predict their orbits far into the future. Those that might one day pose a threat could be watched and given a gentle ‘nudge’ to change their orbit and we may think ourselves safe again. The ‘Domesday comet’ is probably already on its way and will one day reach us. Perhaps in the meantime we may ponder how to divert it. But what about those visitors on a hyperbolic trajectory like Oumuamua and comet Borisov that originate from beyond our solar system? When I first wrote about extra-solar comets and oblique impacts in the early 1990s, the suggestion that comets might strike the Earth was still a toxic subject – until the impact of comet ShoemakerLevy-9 on Jupiter was witnessed on our TV screens. For most of the era of telescopic astronomy, keen amateur observers discovered solar asteroids and comets only when they passed close enough to be seen as tiny objects moving against the stellar background. There was what Stefan Michalowski called the ‘giggle factor’ attached to the possibility of impacts. [1] Eugene Shoemaker declared that the ‘giggle factor’ was gone when we witnessed a comet strike giant Jupiter. Sadly, denial has not gone away, because there remain other unseen dangers that could harm our planet or may have done so in the past. As astronomers probe the universe in new ways, they discover many new phenomena: quasars, pulsars, dark-matter halos, rogue planets, gamma-ray bursts, gravitational waves; all unheard of half a century ago. What next? Catastrophism in Earth history? Many enigmas and possible catastrophic episodes may be cited during human prehistory that demand an explanation as to what could have caused them. The confirmation that an asteroid strike in Yucatan caused the ancient demise of the dinosaurs has set the norm and any suggestion of catastrophic phenomena in more recent Earth history founders on the reply: where is the crater? Even the colossal asteroid impacts that cause mass extinctions would not have sufficient kinetic energy to appreciably affect the Earth’s axis or its orbit. This has long been sufficient for mainstream science to dismiss the idea of changes to Earth’s obliquity and pole shifts during recent prehistory as pseudo-science. This has now become a serious blind spot in our understanding of the past. Gradualist geology and climate science cannot explain the abrupt transitions between glacial periods, and at the end of the Ice Age; or the sharp transitions between stable climate regimes that have occurred during the Holocene. It cannot explain the rapid changes of sea level: the raised beaches and submerged forests that have transpired over the same period. It could not explain the references to astronomical phenomena described in various religious and mythological sources that suggest ancient pole shifts and axis tilts. Gradualist geology could not explain a possible change to the length of day since the earliest calendars. It could not explain climate and sea-level events, such as Joseph’s famine, or Atlantis – or Noah’s Flood. These examples from human prehistory demand a source of high-energy catastrophic events that do not leave an obvious impact crater. They were survivable events (i.e. they were not followed by a mass extinction) yet they possessed sufficient energy to have reset the rotation and climate of the Earth. Here are just a few suggestions based on the latest astronomy and physics. Hyperbolic Exocomets The appearance of comet Oumuamua passing close to us on its hyperbolic trajectory in 2017 has opened minds. Just two years later comet 2I/2019 Borisov was observed with an even higher excess velocity. With two such discoveries within just two years we have to wonder how many earlier examples could have been missed. [see note 1] Astronomers have long been aware of hyperbolic comets with a small excess velocity; but these could be explained as solar comets ejected by a close encounter with one of the planets, only to fall back millions of years later. [2] Oumuamua was a tiny object unnoticed until it was already on its way out of the solar system, most likely an asteroid ejected from its own star system. Its elongated shape (at most 1000 x 100 m) suggests that it is a fragment of a larger planetesimal torn-apart by whatever event projected it into interstellar space. Comet Borisov was somewhat larger and was enveloped in a coma more closely resembling a solar comet – apart from its excess velocity. Just recently (2022) I have noted the possibility of impacts by exocomets mentioned by one of the ‘television academics’, together with another guest who ventured the possibility of oblique ‘bouncing’ impacts that would leave little trace on the Earth’s surface. Such discussion could never have happened in earlier decades. When first I explored such matters in The Atlantis Researches back in the 1990s the concept of impact events was still derided as mere pseudo-science; one simply could not mention such things and be taken seriously. Supernovas and Remnants Astronomers regularly observe supernovas in distant galaxies although none have been observed in our own galaxy in the era of telescopic astronomy. An earlier article Dangers to Earth from Ancient Supernovas examined the question of what happens to the cloud of smaller bodies that must be orbiting a massive star before it goes nova. [3] These may comprise a range from planetesimal-sized objects down to meteorites small enough to hold in your hand. Pieces of the exploding star’s iron and silicon core might also be flung-out by the rapid spin-up of a supernova as it collapses. If these are propelled-away rapidly enough then their kinetic energy would exceed any threat from a solar asteroid. By the time the expanding shell of high-energy meteors reached us it would be so dispersed that they would be millions of kilometres apart. They should arrive with about the same regularity as we observe local supernovae (so about every few hundred years) with impacts being even less frequent. We should only detect such meteors during the brief few days when the shell of solid ejecta passes rapidly through the solar neighbourhood. Around every giant star there must be a region where planetesimals and asteroids orbit in a kind of perverse ‘Goldilocks zone’. The lifetime of a supergiant star is just a few million years; not long enough for planets to coalesce. Before it explodes the star must pass through an expansive Wolf-Rayet phase that would envelop the planetesimals in its gas cloud. Close-in to the final supernova explosion the asteroids would be reduced to dust to become part of the visible remnant, eventually to cool and merge with the interstellar medium. Further out, the expanding shock wave would pass by the asteroids leaving them battered but still in orbit about the collapsed star. Between these two extremes there must lie a zone where the planetesimals are disrupted yet are not reduced completely to dust; fragments of an optimal size would accelerated away by the wind of the supernova. Astronomers observe visible supernova remnants expanding at velocities of 1500 km/s (Crab Nebula) and even 13800 km/s (Cassiopeia A) Compare these to the relatively sedate orbital velocity of Halley’s Comet at 55 km/sec or even the unbound Oumuamua at 87.3 km/sec. One will often see, discussed in various astrophysical papers, the explanation that visible supernova remnants fade as they cool and expand until their density diminishes to that of the interstellar medium. This really amounts to a near-perfect vacuum colliding with an even more perfect vacuum a strange concept! The meteorites that regularly strike the Earth have orbited in the solar wind since the formation of the solar system and have not been halted. If a supernova remnant contains sweptup solid ejecta then, at the hyper-velocities considered, there is nothing in the interstellar medium that could prevent the shells of meteors from expanding long after the visible nebula has faded. Supernovae are not the only potential source of hypervelocity comets and asteroids that could reach the solar neighbourhood. Since the 1950s when Hoyle first proposed the theory of nuclear synthesis in stars the study of stellar collapse has been further refined. Physicists now recognise that even the high densities of a supernova core-collapse are insufficient to explain the abundance of the r- s- and p- process elements heavier than iron and nickel, such as gold, platinum and uranium. To form these heavy nuclei requires the high densities of a neutron star merger – themselves already collapsed supernova remnants. By inference, the presence of these heavy elements on Earth mandates that the primaeval solar nebula must have been preceded by a neutron-star merger. Gamma Ray Bursts Discovered accidentally in the 1960s by Vela satellites monitoring for nuclear tests, these were soon recognised as cosmic in origin, the product of explosions in distant galaxies. Two classes of gamma ray sources are now recognised: long bursts caused by implosion (hypernova) of high-mass luminous stars; and the short bursts attributed to the merger of neutron stars. Such collapses emit polar jets as the particles and radiation are channelled by the magnetic fields. The only reason we observe so many is that their magnitude is so bright that they are visible from the edge of the observable universe. Even then we only see that fraction whose jets are pointed directly towards us. Gamma ray bursts are statistically rare, loosely estimated at a few per million-years in any galaxy; but consider that there must be 180 times this estimate for events where the polar ‘beam’ is not pointed in our direction. Some theories require that the remnant left behind would be a magnetar – a fastspinning neutron star. Some theories even suggest that the Cambrian extinction some 488 million years ago was caused by a gamma ray burst in the solar neighbourhood. However, we need not dwell on the causal mechanism of such events (which is after-all only informed speculation by astrophysicists) rather to consider the solid ejecta and gravitational waves that they must release. FBOTs In 2018 astronomers discovered evidence in distant galaxies for a new class of supernova explosion. These have been termed Fast Blue Optical Transients (or FBOTs). Some have been given convenient nicknames; one explosion, known as “the Cow ”, was observed to be 10-times more powerful than any previously known supernova. [4] Another named “Koala” was almost as bright as a gamma-ray burst. [5] However, while gamma ray bursts may eject just a small mass of high-energy particles and radiation along the polar beams, the FBOTs may launch as much as 10% of our Sun’s mass at relativistic speeds approaching even the speed of light. Unlike a gamma-ray burst, the material ejected by an FBOT leaves the star in all directions. The name derives from the characteristic that the bright flash fades much more quickly than a normal supernova and they are hotter – the high temperature giving them their blue tint. Astronomers theorise that this new class of supernova needs a different mechanism to explain them. One suggestion is a black hole absorbing a white dwarf or a neutron star which then fades rapidly as the remnant falls within the event horizon; alternatively, they may be examples of a core collapse producing a black hole, but in this case the polar ‘beam’ of gamma rays is not pointed directly at us. The focus here has to be on the material expelled by the FBOT at relativistic speeds. Again, such ejecta must comprise small solid bodies, not just streams of hot gas. We may only speculate that the remnant, if we could observe one, would also fade more rapidly that any known remnant nebula. If such explosions can be observed in distant galaxies, then it follows that they must have occurred in the Milky Way galaxy and their nebulae have long ago dispersed and faded – but their shell of ejected meteors, travelling at relativistic speeds, continue to expand. If the supernova creates a central collapsar then its gravity may be enough to pull-back and retain much of the ejecta within the expanding remnant, but not when the parent star has been completely disrupted as in a Type I supernova. Ironically, the least powerful and most common class of supernova may present the greatest danger to us – and once the gaseous remnant has dispersed – totally undetectable by astronomers. Unnovas Another phenomenon related to the fast stars and FBOTs is the Unnova, sometimes misleadingly called a failed supernova. These are very far from failures; they are examples of the most massive stars (yellow hyper-giants of 20-60 solar masses) that try to explode by core-collapse but are too massive and are rotating relatively slowly, such that their light, or anything else, cannot escape from the event horizon. To our eyes the collapsing star would simply pop-out of existence. There are candidate stars that may be examples of this phenomenon; N6946-BH1 was observed to brighten and fade in 2009. The search for such stars has only come to the fore since the millennium as astronomers had been unable to find supernova remnants formed by the most massive supergiants. Once again, we should expect that meteors and comets in just the right orbit might be whipped around such a collapsing star and thus be accelerated into the galaxy at relativistic velocities. This is really no different from the way that hyperbolic solar comets are ejected from our own solar system by close passage to Jupiter or Saturn – except that the velocities are so much higher. We may have an example in one of our galactic neighbours: Cassiopeia A that exploded unnoticed in the mid-seventeenth century. Here astronomers observe not only the rapid expansion of the remnant at 21.6 million km/h, but also a region that is falling back at an equally impressive velocity of 6.9 million km/h; perhaps an indicator that it is under the intense gravitational pull of an invisible former companion star. [6] Consider for a moment how long it might take for supernova ejecta to reach us. To take again the example of Cassiopeia A; if an ejected meteor were travelling at the observed rate of expansion, then at its distance of 10,000 light years it should reach us about 220,000 years from now. The immediate danger would therefore come from a similar supernova that exploded at this distance two hundred and twenty thousand years ago and whose ejecta would only now be reaching us. Of course, the fast meteors and exocomets could approach from various distances and velocities; and from any direction. There is little or no prospect of predicting such arrivals until humans become capable of interstellar travel. Rogue Stars and Planets Other possibilities exist for sources of high-energy ejecta that could reach the earth. At the centre of our galaxy lies a supermassive black hole of 4 million solar masses called Sagittarius A-Star. We have all seen the excellent animations of the closest stars as they are observed to swing around it at velocities so fast that that they can be measured. In 2014 Sgr A* was observed to tear apart a gas cloud surrounding a small star. However, recent analysis would suggest that less than 1% of the matter orbiting the black hole actually falls within its event horizon; the rest is ejected into the galaxy. [7] In 2019 one such fast-star S5-HVs1 was observed to be leaving the galaxy at a velocity of 1700 km/sec. Its track indicates that it has survived a close encounter with Sagittarius A-star. Again we should ask: how many smaller unseen rogue planets, comets and meteors are passing by us at comparable velocities? Answer: there could be billions. No longer is it mere science fiction. Tektites Should one of the hypervelocity fragments from an ancient supernova strike the Earth then what kind of physical evidence might we expect it to leave behind? Certainly not a crater, any more than you would expect a bullet from a gun to leave a crater in soft material. However the science of bolide ballistics does give us useful analogies. Most likely they would drill a hole deep into the mantle before being dissolved, or perhaps a ricochet scar from an oblique impact. The most likely hard evidence would be a strewn field of micro-tektites (impact glass) around the point of entry. We are considering here a football-sized body, or even smaller, travelling so fast that that they could penetrate to the mantle. We should expect the impact site to be inconspicuous and disguised by infill or volcanic extrusions. [8] Tektite Strewn Fields. Most of the largest are millions of years old are linked to ancient craters. Examples of Holocene age are likely to be microtektite sites, too small to show on a large-scale map. Prime locations to search for hard evidence would be the smallest tektite fields that are not associated with any known crater; and always bear in mind that three-quarters of all impacts must occur in the ocean leaving even less accessible evidence. It may be easier to find one on the Moon, where there has been less geology to conceal them. We shall see. Very little physical evidence would remain on the Earth’s surface after a few hundred years but we may still detect short-lived radioactive isotopes that were synthesised in the parent supernova. New Physics If you wish then you can look into the more speculative and exotic phenomena that astronomers and physicists now consider possible. Gravitational Waves Long theorised but first detected in 2015, these are thought to be produced by the mergers of massive objects such as neutron stars and black holes. They must also occur when stars fall into Sagittarius Astar and when galaxies and supermassive black holes merge: a frightful concept! All the events so-far detected by the most sensitive gravitational wave detectors on earth result from mergers of collapsed stars in distant galaxies. Typically the amplitude of the waves is less than the width of a human hair and would go unnoticed – each of us has probably experienced numerous gravitational waves during our lifetime; it is no different to the radio waves and neutrinos that pass through us all the time. A gravitational wave is a stretching and squeezing of the space-time fabric produced by high gravity events. Atoms and particles, as well as planets (which are merely large groups of atoms for this example) would alternately stretch and squeeze according to the wavelength. It is important to visualise that it is the spacetime structure that deforms not the matter that occupies it. Precisely what we would feel from a gravitational wave that originated much closer to us could only be speculation and imagination at this point. Whatever else, the gravitational wave has a point of origin and a direction. It carries energy and it should affect the Earth in the same way as any other impulse. It would act to change the angular momentum of the planet, resulting in a nutation of the axis and could even alter the length of day. A change to the shape of the Earth (the squeezing and pulling) must also trigger a wobble and a pole shift. The real difference however, between this and the impulse delivered by an impact event, is that it should leave no crater or any other hard evidence on the surface. A gravitational wave would not have to be spectacular to cause geological effects; a variation of perhaps a few millimetres might be enough to trigger worldwide earthquakes and flows of magma in the core and mantle, thus altering the shape of the geoid and its rotational balance. The rest is then just known geophysics. Once again, it is important to appreciate that although physicists may talk as if they know what is going-on, they don’t! No-one really understands gravity! Mini-black-holes The only known process by which a black hole could be created is by the gravitational collapse of a massive star at the end of its life, such that the core falls within its event horizon and the required escape velocity exceeds the speed of light. To form a stellar black hole, the collapsed core must be of a minimum of about 2 solar masses, commencing as a supergiant of 25+ solar masses, The resultant black hole would occupy a diameter of about 25 km. However, there is no minimum size limit so long as the required density could be achieved. Scientists such as Jakub Scholtz and James Unwin propose that in the extreme conditions of the early universe, local unevenness could have created conditions where matter was clumped sufficiently for mini black holes to form. They suggest that the as yet unobserved Planet 9 could be a primordial black hole about the diameter of a tennis ball. [9] Some primordial black holes might be no bigger than fundamental particles. Once in existence, these would behave like any other massive object subject to gravity as the universe expanded; most falling into supermassive black holes and stars or orbiting them. This raises the obvious question why are there not one or two orbiting the sun; are they the missing ‘dark matter’, etc. Popular science-fiction would give us the notion that we would be sucked into such a black hole, but this is erroneous; from distance they would represent no more danger than a rock of similar mass. However, there is always the possibility that a close fly-by could produce tidal effects in the oceans and crust; and resultant catastrophism as has been proposed by other authors. The mini-black-hole theory is not one that that I favour but is listed here for completeness. Gravity Leaks? What is gravity? If you know then please tell the physicists. Modern astrophysicists can tell you how it behaves, building upon Einstein’s relativity; they can even suggest that the newly-confirmed Higgs Boson confers mass; and it is the mass (whatever that is) that bends the space-time fabric; but this merely transfers the problem to a deeper level of unknown. A stellar cast of physicists at LIGO sought to use gravitational waves as a way to probe whether gravity was ‘leaking’ from our universe into an adjacent parallel universe. They seem to be convinced that it does not; but what about gravity leaking into our universe from an adjacent one? This conundrum derives from the multiverse theory, whereby an infinite series of parallel universes or ‘branes’ must exist in parallel, splitting-off at quantum level. These other universes would be ‘stacked’ adjacent to our own in a fourth dimension, each a Planck distance apart – rather like twodimensional sheets of paper stacked in the third dimension. Gravity obeys an inverse square law; that is to say, it’s strength is inversely proportional to the square of the distance from the source. Therefore it is reasonable to suggest that its influence in the higher dimensions would obey the same law. The gravity that we experience is therefore just a fraction of the total force, which could explain why it is so weak compared to the other fundamental forces. This raises the possibility that the Earth may pass close to a source of mass (a planet or star) lying in an ‘adjacent’ universe and if it be close enough then its gravity would be felt in our own. These are the science fiction ‘gravity anomalies’ that you may see on an episode of Star Trek – gravitational pull emanating apparently from nowhere! Indeed it is such a difficult concept that there is not even adequate language to describe it. All we really need to consider is that the gravitational effect of a mass in an adjacent universe should be similar to gravity from a mass in our own universe. However, such physics as is published would suggest that the body must approach extremely close – almost passing through us – in the higher dimension in order for us to experience its effects. Perhaps we should not worry about this idea until a physicist can explain what dark matter is and where it is. Conclusions If we observe exocomets then there must also be many smaller exo-meteors. If we can watch highenergy phenomena occurring in distant galaxies then they must also occur in our own galaxy. Because we only see the rare phenomena during our short human timeframe we fail to perceive the long-term threat that they pose. It is rather like building your house close to a volcano and relying on the security that it has never erupted in your lifetime. We cannot do much about the future, but we can at least recognise the effect they might have had in the past and consider their effect on recent geology and human prehistory. It is unfortunate that so much discussion of catastrophism in prehistory during the twentieth century was so unempirical that it could be easily demolished by scientists. This has led to a neglect and unwillingness by mainstream geologists to consider the question for fear of professional ridicule. It is a subject that must be considered. All of the phenomena suggested above could cause cataclysmic episodes on the Earth and yet they would not leave any hard evidence on the surface. Let me pose you a troubling series of questions. How do you know that there is not a dark collapsar lurking, a few thousand light-years from earth, that ‘exploded’ millennia ago and sent a shell of meteors in our direction at unthinkable velocity? Is there a dark star awaiting discovery in our galactic locality, of just the right mass that may collapse further and send a gravitational wave in our direction disturbing our stable rotation as it passes through us? What would that feel like and what might its geological effects be? Is there a planet in an adjacent parallel universe that may pass close-enough in a higher dimension for its gravity to leak into our own? Are you waiting for a recognised ‘expert’ or professor to tell you whether such concepts are real or pseudo-science? Another definition of pseudoscience might be science that your expert has not yet thought of, or perhaps fears to mention lest their papers be rejected. Beware the giggle factor! Note 1: As this article was in preparation, evidence was released that a 0.45m diameter meteor estimated to be travelling at 210,000 km/h (58.33 km/sec) broke apart in the atmosphere over New Guinea in 2014. This discovery actually predated Oumuamua but was awaiting conclusive verification of the data. As may be noted from the above discussion this velocity is still far below the maximum that could be generated by stellar phenomena, but well above the commonly observed velocities for meteorites of solar system origin. The authors suggest that the bolide came from the inner part of a planetary system in the disk of the Milky Way galaxy. [10] Note 2: Again as this article was in preparation, evidence was published that a bolide discovered in Egypt in 1996 known as the Hypatia stone was probably an ancient meteorite of non-solar-system origin. The composition was so unusual that the researchers suggest it was most likely produced in a Type 1a supernova. The conservative research suggests that it formed in a region of interstellar dust within the proto-solar nebula, which preserved its origin, rather than suggesting that it formed around another star. [11] Alternatively, it could be evidence that not all meteors ejected from supernovas will be travelling at hypervelocity. Relevant Hyperlinks https://solarsystem.nasa.gov/asteroids-comets-and-meteors/comets/2I-Borisov/in-depth/ https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1991JBAA..101..119H&defaultprint=YES&filetype=.pdf https://arxiv.org/abs/2201.08911 https://www.thoughtco.com/eye-of-the-sahara-4164093 https://astrobites.org/2011/10/24/the-case-of-the-disappearing-star-un-novae-and-ultra-long-gamma-ray-transients/ https://en.wikipedia.org/wiki/N6946-BH1#/media/File:PIA21467.jpg https://en.wikipedia.org/wiki/Failed_supernova https://hubblesite.org/contents/media/images/2017/19/4039-Image.html?news=true https://www.nasa.gov/mission_pages/chandra/multimedia/black-hole-SagittariusA.html https://en.wikipedia.org/wiki/File:SgrA2018.gif https://www.universeguide.com/fact/hypervelocitystars http://www.sci-news.com/astronomy/s5-hvs1-hypervelocity-star-07799.html https://geologyscience.com/gallery/eye-of-the-sahara-or-richat-structure/ https://www.scientificamerican.com/gallery/the-smallest-known-black-hole/ https://arxiv.org/abs/1811.00364 https://www.forbes.com/sites/startswithabang/2019/03/15/this-is-why-the-multiverse-must-exist/?sh=15cca9566d08 https://public.nrao.edu/gallery/category/supernova-explosions-and-supernova-remnants/ https://www.space.com/38471-gravitational-waves-neutron-star-crashes-discovery-explained.html https://www.sciencedirect.com/science/article/pii/S0016703718301236 https://public.nrao.edu/gallery/category/supernova-explosions-and-supernova-remnants/ https://ntrs.nasa.gov/api/citations/19980007188/downloads/19980007188.pdf https://www.iac.es/en/outreach/news/astronomers-discover-first-supernova-explosion-wolf-rayet-star https://www.msn.com/en-gb/news/techandscience/this-tiny-space-rock-might-be-the-1st-physical-evidence-of-araresupernova/ar-AAXx692?ocid=msedgntp&cvid=c0c26c401fce47ecb84ab52edc4b1d1a References 1 'Giggle factor' is no laughing matter to scientists, Posted 3/11/2003 8:53 PM, by Eric J. Lyman, Special for USA TODAY. 2 Hughes, D.W. (1991) On Hyperbolic Comets, J. Br. Astron. Soc. 101, 2, 1991 3 Dunbavin, Paul (2020) Dangers to Earth from Ancient Supernovas, in Prehistory Papers, pp 1-12, Third Millennium Publishing, Beverley, ISBN: 978-0-9525029-4-4 4 Swift spectra of AT2018cow: A White Dwarf Tidal Disruption Event? https://arxiv.org/abs/1808.08492 5 Ho, Anna Y. Q. et al (2020) The Koala: A Fast Blue Optical Transient with Luminous Radio Emission from a Starburst Dwarf Galaxy at<i>z</i>= 0.27, The Astrophysical Journal, 859, 1 https://iopscience.iop.org/article/10.3847/1538-4357/ab8bcf 6 Vink, J. et al (2022) The forward and reverse shock dynamics of Cassiopeia A https://arxiv.org/abs/2201.08911 7 Wang, Q.D. et al (2013) Dissecting X-ray-emitting Gas around the Center of our Galaxy, arXiv:1307.5845 [astro-ph.HE] or arXiv:1307.5845v2 [astro-ph.HE] https://doi.org/10.48550/arXiv.1307.5845Rogue stars (Wang?) https://arxiv.org/pdf/1307.5845.pdf 8 Petersen, Carolyn Collins. "What Is the Eye of the Sahara?" ThoughtCo, Aug. 27, 2020, thoughtco.com/eyeof-the-sahara-4164093. 9 Scholz, Jakob and Unwin, James (2019). What if Planet 9 is a primordial Black Hole? https://arxiv.org/pdf/1909.11090.pdf 10 Amir Siraj, Abraham Loeb, The 2019 Discovery of a Meteor of Interstellar Origin https://arxiv.org/abs/1904.07224 11 Jan D. Kramers, Georgy A. Belyanin, Wojciech J. Przybyłowicz, Hartmut Winkler, Marco A.G. Andreoli, The chemistry of the extraterrestrial carbonaceous stone “Hypatia”: A perspective on dust heterogeneity in interstellar space, Icarus, 382, 2022, 115043, ISSN 0019-1035 https://doi.org/10.1016/j.icarus.2022.115043 https://www.sciencedirect.com/science/article/pii/S0019103522001555 Tags: Ancient Astronomy, catastrophism, pole-shift, Chandler wobble, impact event, comet impact, Oumuamua, gravitational wave, supernova, supernova remnant, stellar-merger This is a format-adapted version of that originally published in 2022 as an interactive webpage at: https://www.third-millennium.co.uk/supernova-ejecta-and-the-dangers-to-earth Citation: Dunbavin, Paul (2022) Supernova Ejecta and the Dangers to Earth, in Prehistory Papers II, pp 1-17, Third Millennium Publishing, Beverley, ISBN: 978-0-9525029-5-1