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from the supernovae-have-that-effect-on-planets dept.
Researchers consider whether supernovae killed off large ocean animals at dawn of Pleistocene
About 2.6 million years ago, an oddly bright light arrived in the prehistoric sky and lingered there for weeks or months. It was a supernova some 150 light years away from Earth. Within a few hundred years, long after the strange light in the sky had dwindled, a tsunami of cosmic energy from that same shattering star explosion could have reached our planet and pummeled the atmosphere, touching off climate change and triggering mass extinctions of large ocean animals, including a shark species that was the size of a school bus.
[...] The effects of such a supernova — and possibly more than one — on large ocean life are detailed in a paper just published in Astrobiology.
[...] A supernova 2.6 million years ago may be related to a marine megafaunal extinction at the Pliocene-Pleistocene boundary where 36 percent of the genera were estimated to become extinct. The extinction was concentrated in coastal waters, where larger organisms would catch a greater radiation dose from the muons.
According to the authors of the new paper, damage from muons would extend down hundreds of yards into ocean waters, becoming less severe at greater depths: "High energy muons can reach deeper in the oceans being the more relevant agent of biological damage as depth increases," they write.
Indeed, a famously large and fierce marine animal inhabiting shallower waters may have been doomed by the supernova radiation.
"One of the extinctions that happened 2.6 million years ago was Megalodon," Melott said. "Imagine the Great White Shark in 'Jaws,' which was enormous — and that's Megalodon, but it was about the size of a school bus. They just disappeared about that time. So, we can speculate it might have something to do with the muons. Basically, the bigger the creature is the bigger the increase in radiation would have been."
Megalodon (Carcharocles megalodon).
Hypothesis: Muon Radiation Dose and Marine Megafaunal Extinction at the End-Pliocene Supernova (DOI: 10.1089/ast.2018.1902) (DX)
(Score: 2) by MichaelDavidCrawford on Friday December 14 2018, @03:29PM (5 children)
We know this because of the abundance of such heavy elements as Uranium. First-gen stars won't have any heavy elements because it consumes energy to make them - everything heavier than iron consumes energy to make, while making anything lighter creates energy.
Among the things I keep myself awake all night is, what would happen to us if a nearby star went supernova? It's not like we could outrun it.
For that to be a problem, a star would have to be both blue and bright: only massive stars are blue, while only nearby stars are bright. How many bright blue stars are within the same distance as this one was?
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(Score: 3, Informative) by bzipitidoo on Friday December 14 2018, @05:28PM
> First-gen stars won't have any heavy elements because it consumes energy to make them
They will have smaller quantities of heavy elements, but there will be some.
> Among the things I keep myself awake all night is, what would happen to us if a nearby star went supernova? It's not like we could outrun it.
Fortunately, for tens of thousands of years, there won't any big, aging stars near enough to kill us by going supernova. The "kill zone" is thought to be about 50 light years. Betelgeuse gets a fair amount of talk, because it's expected to go supernova sometime in the next million years. But it's 640 light years away, so no problem. Another possibility is to be so unfortunate as to have the pole of a more distant supermassive star aimed our way when it blows. Eta Carinae could do us in that way, but its poles aren't pointing at us, so no worries there. The disk shape of the galaxy and the natural tendency of the poles of stars to be aligned with that of the galaxy means there's very little that could be pointed at us.
Nuclear war and global warming are more pressing problems.
(Score: 3, Interesting) by legont on Friday December 14 2018, @05:51PM (3 children)
Actually, just a supernova is not powerful enough to create uranium, gold and such in quantities we have. I'd take two supernovas creating neutron stars that would then collide. https://wtop.com/the-space-place/2017/10/wondrous-discovery-kilonova-may-explain-gold-platinum-uranium-created/ [wtop.com]
No wonder we are so violent;)
What would be interesting to see is the light of a supernova nearby so a defined doomsday would be set. Do you think we'd join forces and do something about it?
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(Score: 3, Interesting) by HiThere on Friday December 14 2018, @07:34PM (2 children)
Uranium is too common for the source to be an event both that rare and that small. A galactic core explosion might to it, or smaller or more common phenomenon.
FWIW, the normal percentages of elements cause me to think that we might live in a second generation galaxy.
P.S. Reply to a post further above...
First generation (in the universe) stars would have only Hydrogen and Helium, and scant, scant, scant traces of heavier elements to work with. OTOH, I accept that first generation (in this galaxy) stars would have a much richer blend. I think the term "first generation stars" is used in a confusingly ambiguous way, sometimes meaning one of those concepts and sometimes the other.
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(Score: 3, Interesting) by legont on Friday December 14 2018, @09:21PM (1 child)
It's the first time I've heard about "galactic core explosion". https://www.starburstfound.org/superwave/Galactic.html [starburstfound.org]
How close is this to the mainstream? The article above implies rather frequent showers from our center. Way more frequent than supernovas in the vicinty.
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
(Score: 3, Interesting) by HiThere on Saturday December 15 2018, @12:27AM
Well, really I should have referred to "Seyfert Galaxies" or some such, but Niven's phrase stuck in my memory, even if he was quite wrong. (He wasn't attempting to be right, just plausible and interesting...which it was.)
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