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Nemesis
YetAnotherOne writes: "Intersting article on yahoo about the possibility that our Sun has a companion star, Nemesis. This would explain some bizarre theory that mass extinction on Earth has a periodicity of 26 million years. Nemesis' perihelion pass would cause Oort cloud comets to rain in!"
> Granted it's supposedly a red dwarf which wouldn't
> give off too much light, but at 1-3 lys away, it should
> show up fairly brightly, I would guess.
There's also the possibility that it is a brown dwarf, barely visible at all. A previously unknown brown dwarf was recently discovered only 13 ly from Earth, purely by chance as I recall.
>but at 1-3lys away, it should show up fairly brightly, I would guess.
Nope, young low mass brown dwarfs *may* be visible (they glow from the heat of gravitational contraction and not thermonuclear burning) but any brown dwarf older than 1 Gigayear would be virtually undetectable even within 0.4 light years. There could be many candidates in the solar neighbourhood, but they're just so damn faint...
Time to but a bigger telescope!
This binary system idea seems to be a point attractor for weird and complex theories.
This is my favorite:
http://www.darkstar1.co.uk/
It explains everything from Sumerians to Sirius. All for your viewing pleasure.
The Assayer - free-information book reviews
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No. The shifts in the wavelength spectrum are caused by changes in relative velocity (same as an ambulance siren rising in pitch as the ambulance drives towards you, then falling as it passes and moves away). The distance to the star makes no difference to the size of the shift - only it's velocity relative to us is important. The reason it doesn't help in this case is that the star, if it exists, has a very long orbital period around the sun, making it's closest approach into the Oort Cloud only once every 26 million years. So, you'll only see the spectrum change from blue- to red-shifted if you observe it over tens of millions of years.
I'm sure that we won't be able to watch the blue to red-shift occur, but rather that we could possibly see what side of the orbit we were on (in order to see how many million years we have left).
But aside from that, I was wondering why something so close wouldn't have a higher luminosity than other stars that are much further away. Granted it's supposedly a red dwarf which wouldn't give off too much light, but at 1-3lys away, it should show up fairly brightly, I would guess.
Dancin Santa
As for the 26 million year period itself, Scientific American offers some information.
intersting stuff!
Chris Cothrun
Curator of Chaos
Bleh!
This would mean that once every 30 million years that hypothetical companion star of the Sun would pass through the Oort cloud (a hypothetical cloud of proto-comets at a great distance from the Sun). During such a passage, the proto-comets in the Oort cloud would be stirred around. Some tens of thousands of years later, here on Earth we would notice a dramatic increase in the the number of comets passing the inner solar system. If the number of comets increases dramatically, so does the risk of the Earth colliding with the nucleus of one of those comets.
When examining the Earth's geological record, it appears that about once every 30 million years a mass extinction of life on Earth has occurred. The most well-known of those mass extinctions is of course the dinosaur extinction some 65 million years ago. About 15 million years from now it's time for the next mass extinction, according to this hypothesis.
This hypothetical "death companion" of the Sun was suggested in 1985 by Daniel P. Whitmire and John J. Matese, Univ of Southern Louisiana. It has even received this name: Nemesis. One awkward fact of the Nemesis hypothesis is that there is no evidence whatever of a companion star of the Sun. It need not be very bright or very massive, a star much smaller and dimmer than the Sun would suffice, even a brown or a black dwarf (a planet-like body insufficiently massive to start "burning hydrogen" like a star). It is possible that this star already exists in one of the catalogues of dim stars without anyone having noted something peculiar, namely the enormous apparent motion of that star against the background of more distant stars (i.e. its parallax). If it should be found, few will doubt that it is the primary cause of periodic mass extinctions on Earth.
But this is also a notion of mythical power. If an anthropologist of a previous generation had heard such a story from his informants, the resulting scholarly tome would doubtless use words like 'primitive' or 'pre-scientific'. Consider this story:
This is why some scientists thought this Nemesis theory was a joke when they first heard of it -- an invisible Sun attacking the Earth with comets sounds like delusion or myth. It deserves an additional dollop of skepticism for that reason: we are always in danger of deceiving ourselves. But even if the theory is speculative, it's serious and respectable, because its main idea is testable: you find the star and examine its properties.
However, since the examination of the entire sky in the far IR by IRAS with no "Nemesis" found, the existence of "Nemesis" is not very likely.
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