Essentially the Nemesis theory comes from research done by David Raup and Jack Sepkoski. Back in 1984 they published a paper claiming that there was a statistically relevant periodicity over the last 250 million years. Basically they identified 12 big extinction events, averaging 26 million years between each of them.
Now, 1984 is a long time ago. We didn’t even really have cell phones back in ’84, but more recent research supports the Raup and Sepkoski work. In a new study Adrian Melott of the University of Kansas and Richard Bambach of the National Museum of Natural History in Washington, D.C. confirmed the extinction cycle, although they noted that sometimes extinctions happen in the middle of a cycle and occasionally a peak will happen when nothing happens at all.
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| Any time this doesn’t happen is a good time. Credit |
And before you get your knickers in a bunch, remember that 26 million years is a darned long time. The entirety of human history is only about 6,000 years old and homo sapiens have really only been around for 2.5 million years. Depending on who you talk to we have between 16 and 21 million years until the next peak.
But the scientists couldn’t find a source for the regularity of the extinction events, what was it that was causing it all? The period of the cycle gave them an idea.
“If you see something with a very regular cycle that’s like 10 million or 100 million years, you tend to think of things astronomical,” said Melott later about the study. “For example, the galaxy takes about 250 million years to orbit once.”
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Raup and Sepkoski knew that at least two of the extinction events coincided with large impact events and so they suggested that there could be some kind of extra-terrestrial source causing them.
See, beyond our solar system is a vast cloud of icy objects called the Oort Cloud- the birthplace of comets. Most of the comets that end up in our neck of the inner solar system seem to come from the same region of the Oort Cloud, and it’s been suggested that if our sun was part of a binary star system, where two stars orbit a common center of mass, this rotation could send comets towards us on a regular basis.
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Other evidence for nemesis lies in a recently discovered dwarf planet named Sedna. It’s a dwarf planet a little larger than Pluto, and has an orbit ranging from 76 to 975 times the distance between the Earth and the Sun (also known as an AU). Sedna takes over 11 thousand years to orbit the sun, but the strangest thing is that it’s existence doesn’t seem to make sense.
“Sedna shouldn’t be there,” said Sedna discover Mike Brown of Caltech,. “There’s no way to put Sedna where it is. It never comes close enough to be affected by the Sun, but it never goes far enough away from the Sun to be affected by other stars.
The very nature of the Oort Cloud around our solar system also support the idea of Nemesis. The edges of our Oort Cloud are sharp, which is usually noted in binary star systems. Most single star systems have Oort Clouds with diffuse edges.
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| Rendition of the mysterious Oort Cloud. Credit |
But is it really possible that there could be another sun beyond our solar system? Yes, but not the same type of sun that we have. Scientists say that a brown dwarf star could exist in our outer solar system, especially since they are so much smaller and cooler than our sun that they don’t shine brightly. Although they are thought to be common we have such difficulty seeing them in our telescopes that we only know of a few hundred of them.
If Nemesis did exist as a brown dwarf, it would be about 1 to 1.5 light years away from us right now. We’ll know for sure soon either way, because the current Wide-field Infrared Survey Explorer (WISE) should complete its mission by mid 2013. Wise is an infrared telescope searching the entirety of the night sky for sources of heat and should be able to spot a brown dwarf in our outer solar system.
Other scientists think it’s more likely that Nemesis is a low mass object like a planetoid rather than a red dwarf. Davy Kirkpatrick at NASA’s Infrared Processing and Analysis Center at Caltech thinks it will be about 3-5 times the mass of Jupiter (although it would be about the same size since degenerate pressure causes massive gas giants to only increase in density relative to their mass).
But these scientists think that while the object is affecting planetoids like Sedna, they don’t think that this object is really disrupting the Oort cloud and sending us comets though, and because of that they prefer a different name for it without any of the negative connotations of “Nemesis:” Tyche.
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| I guess this is a nicer looking statue? Maybe… I don’t think the Nemesis statue had her stepping atop another person. Credit |
But it’s important to note that however you look at the hypothesis the idea of periodic mass extinctions is still debated to this day. Even if there is a pattern, there’s no guarantee that they’re caused by foreign objects. In fact, the Permian–Triassic extinction event (also known as the Great Dying) seems to be caused not by a comet, but by the entirety of Siberia erupting in a mass of lava. Others argue that the fossil record isn’t long or accurate enough to really establish such a cycle in the first place.
Some researchers, including Melott, argue that such a wide orbit is inherently unstable and could not have lasted long enough to cause all the regular extinctions in the fossil record.
“If Nemesis existed and had this kind of an orbit, its orbit would not be regular,” Melott told SPACE.com. “Calculations indicate its orbit would change by 20 to 50 percent due to the gravitational attraction of stars as they pass by us, and the movement of the sun in the galaxy.” An object like Nemesis would have irregularities in its orbit and thus could not be the cause for such a regular cycle.
There are counter-theories in place about the sharp-edged Oort Cloud pattern with people arguing that it could be an angular effect of the galactic gravity plane, which is nearly the same theory to explain regular comet bombardments without Nemesis.
Plus WISE isn’t the only infrared sky survey to be completed, and none of the other surveys noticed anything like Nemesis.
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It’s also important to note that we’ve seen stuff like this before. Back in the early 1900’s people were looking for a huge planet in the outer solar system to explain the way that Neptune moved in its orbit. Some calculations at the time showed that it was being tugged by something massive, calculations that later turned out to be false. But at the time everyone was certain that there had to be something big out past Neptune.
Any way you look at it though, a million years is an awfully long time, and it’s even more difficult to think about things in terms of many millions of years. We have quite a long time to figure it out- before we’re due for a new peak of catastrophes.
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| Guess I’ll have to use my bomb shelter as a lounge area instead. Credit |