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Nemesis, the Sun's Binary Star Companion?
0xC2 writes "The Binary Companion or 'Nemesis' theory asserts that a yet-to-be discovered companion to our Sun may actually exist. Recent observations of two nearby stars (assumed companions) show debris disks 'strikingly like the Kuiper Belt int the outer part of our Solar System'. The Binary Research Institute site is devoted to the theory, and presents a concise introduction, list of evidence, and sample calculations in support of the theory. A fascinating read, although the physics and related calculations are not trivial." Has the 'unique theory on the internet' vibe to it, but interesting nonetheless.
An actual brown dwarf isn't likely given scarce evidence but there seems to be reason to believe there are one or more large Kupier Belt objects yet to be found. I've read about gravitational anomalies for years now but they just don't seem large enough to indicate a failed star close enough to call us a near miss binary system. I guess if all the outer planets merged we'd have the makings of a brown dwarf but as we are the system seems to be one of those rare single star systems.
SETI is the Search for Extra Terrestrial Intelligence, they do not involve themselves often in cosmological debates, instead they focus on mapping radio signals from numorus star systems. The radio signals they recieve however have led cosmologists to discover a number of special objects in space.
NASA might have been a better choice for inclusion in your parent post, or better yet a astonomological group.
It was David Raup and John Sepkoski who argued for 26-million year periodicity, using a statistical analysis of the fossil record; others argued that this was just a statistical artifact. These days, the idea looks hard to defend. The problem is that periodicity implies a common mechanism for mass extinctions. However, while some extinctions seem to have been caused by comet or asteroid impacts (such as the Triassic mass extinction that gave the dinosaurs their opportunity, and the Cretaceous mass extinction that later did in the dinosaurs), the mother of all mass extinctions, the Permian event, appears to have been caused by massive volcanic eruptions. Which is kind of a pity, because it's an interesting idea.
The linked article is not really about Nemesis, a distant companion to the Sun supposedly linked to regular massive exctinctions through its influence on the Oort cloud (where comets come from).
It is, however, about an unseen Sun companion responsible for the precession of the equinox. The precession of the equinox is the observation that as the Earth orbits the Sun, after a full year around the Sun the Earth does not realign itself with the distant stars, there is a difference of about 50 arcseconds. This correspond to a period of about 24,000 years.
Current theory for precession says the phenomenon is due to tidal effects due to the Moon acting on the non-perfectly-spherical Earth.
TFA makes the simple point that this could be also more easily explained if the Sun was revolving around an heretofore unseen companion for the same period. This would also explain a number of other more complex phenomena, such as why this the precession rate seems to slowly, but undoubtedly change with time, why the angular momentum of the Sun appears to be so low compared to that of the planets, etc.
TFA goes on to make prediction where this companion might be in the sky, and how far away it should be (between 0.01 and 0.03 of a LY), using nothing more complicated than basic Newtonian celestial mechanics.
Well, time will tell, and I'm not an astronomer, but the theory is actually very simple and testable (in the mid to long run), so either evidence will mount in this direction or it will be disproved.
For example we could measure precession rates on Mars. Since Mars has no large satellite, if it is found to have a precession rate similar to that of the Earth, then this will be very strong evidence that the tidal theory cannot be correct, and that the distant companion one is more likely to be. On the other hand if precession on Mars is very low, then this theory cannot be correct.
In short I think the guy might be wrong but he is no crackpot.
Wouldn't it be possible for a large metereor/meterorite (dammit, which is the correct term for one that actually hits?) to actually cause volcanic events? If a big one hits, and punchs a nice old hole in the crust, lots of mantle would come bubbling up, right? All kinds of tectonic aftershocks too. Or is that farfetched?
"I'm not sure if I can agree with your magnitude numbers for a brown dwarf."
I got the +17 number from here. For the record, 17 is pretty damned dim: Proxima Centauri has an absolute magnitude of 15.49. But even if you unrealisticly want to bump up Nemesis' absolute magnitude to 30, at 100,000 AU (twice your largest claim) it'd still have an apparent magnitude from earth of 24, still 16 times brighter than what modern ground-based telescopes can see. All you'd be doing is limiting the data that should be available on Nemesis to 80 years instead of 120.
"Each of these brown dwarfs are warm objects that emit a reasonable amount of infrared radiation. If it is a cold black dwarf similar to a larger Uranus--~60 K (and less than 13 Jupiter masses so that it can't have fusion)"
Aside from the fact that we'd still be able to see it, with 13 Jovian masses at 25,000 AU (half your smallest claim), the gravitational attraction on the sun would be 0.117 pm/s^2 (that's picometers). The center of the galaxy exerts an acceleration on the sun of 19,330 pm/s^s. Nemesis' gravitational influence would be indiscernible and meaningless compared to the gravitational effect of the rest of the galaxy. Its influence on us would literally be background noise, unless one tries to claim it influences us in some way other than gravity (*cough* astrology *cough*)