Thread: Nemesis theory
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Apr10-06, 10:56 AM
Sci Advisor
PF Gold
P: 4,014
In terms of the original idea (a small star, or super-Jupiter, in a highly elliptical orbit, stirring up the Oort cloud and so creating mass extinction events here on Earth), it's dead - the periodicity in the fossil record is far from clear, there is no corresponding record of contemporaneous impacts on other solar system bodies, mass extinctions on Earth - with one notable, and possible two or three less notable, exceptions - cannot be tied to any impacts (by any of the usual measures), etc, etc, etc.

In terms of the observational data, it's pretty clear there are no red dwarfs close enough to be in any quasi-stable orbit, nor white dwarfs. Brown dwarfs are not yet fully ruled out, but the region of parameter space they could inhabit, undetected to date, is small.