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Space Science

Nemesis 13

Posted by michael from the call-in-liv-tyler dept.
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!"
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Nemesis More

Nemesis

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  • Nightfall? (Score:1)

    by Anonymous Coward
    Reminds me of an Asimov story of a rare solar eclipse on a planet with three suns. A group of people found that periodically civilization would be thrown back to the stone age and build itself back up, believed to be caused by the sky going black. No one believed them until night fell.

    Anyway, I have to ask:
    When was the last catastrophic comet shower?
    One million years ago? 26 million years ago?

    One of them mentioned they didn't expect the human species to last 26 million years. So, what would cause the end of the human species before then? Mad cow disease? An asteroid (like "Deep Impact" or "Armageddon")? Borg invasion? Evolution?

    I realize this guy wants desperately to have his theory proved/disproved conclusively, but it's going to be hard to find funding if his findings will have little impact on Joe/Jane Public. Especially given the general state of the economy and that any effect it will have on Earth will not be seen while any of us are alive.

  • Nemesis? (Score:1)

    by Anonymous Coward
    I think I remember reading that book
    • Nemesis
    by Isaac Asimov. I think that star is on a collision course with Earth. Also, all we need to do is send Super Luminal ships back and forth in front of the star to change the path of Nemesis enough to save our planet. Those Rotorians cannot escape us!
  • Asimov's book on Halley's Comet when it came around in the 80s discussed the Nemesis theory.

    --
    Marc A. Lepage (aka SEGV)
  • Last I heard, this idea was right out the window. The current idea about the "periodic" extinctions (they're not, really) is that they are caused by the solar system moving through the galactic plane.
  • This theory has been around since the early 1990s.
  • > 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/ [darkstar1.co.uk]

    It explains everything from Sumerians to Sirius. All for your viewing pleasure.
  • Actually it's nearly 20 years old. Muller wrote a book [amazon.com] about it. When I took physics from him at Berkeley ca. 1983, he was talking like it would get found in a survey fairly soon. It's also hard to know how much faith to put in the supposed periodicities of the mass extinctions -- it depends on stuff like which dates you decide are reliable enough to include in the analysis.


    The Assayer [theassayer.org] - free-information book reviews

  • Wouldn't a star orbiting that close have a fairly easily recognizable wavelength shift, red if leaving, blue if coming?

    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

  • A little bit of thought (Score:3)

    by crisco ( 4669 ) on Monday April 09, 2001 @11:03AM (#309820) Homepage
    The sun's orbital period around the galaxy is approx. 250 Million years(from this page [otterbein.edu]). Presumeably we pass though the galactic plane twice? That doesn't match the supposed 26 million year period. This page [morrison.co.us] offers some alternate explanations, including the idea that it isn't the galactic plane but several dust clouds that we might pass through (dust being relative, certainly containing particles large enough to change conditions here on earth maybe?).

    As for the 26 million year period itself, Scientific American [sciam.com] offers some information.

    intersting stuff!

    Chris Cothrun
    Curator of Chaos

  • Suppose our Sun was not alone but had a companion star. Suppose that this companion star moved in an elliptical orbit, its solar distance varying between 90,000 a.u. (1.4 light years) and 20,000 a.u., with a period of 30 million years. Also suppose this star is dark or at least very faint, and because of that we haven't noticed it yet.

    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:

    There is another Sun in the sky, a Demon Sun we cannot see. Long ago, even before great grandmother's time, the Demon Sun attacked our Sun. Comets fell, and a terrible winter overtook the Earth. Almost all life was destroyed. The Demon Sun has attacked many times before. It will attack again.

    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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