[meteorite-list] Nemesis

From: Rob Matson <mojave_meteorites_at_meteoritecentral.com>
Date: Mon, 6 Sep 2010 12:52:15 -0700
Message-ID: <GOEDJOCBMMEHLEFDHGMMAEFEEFAA.mojave_meteorites_at_cox.net>

Hi Steve,

> I Just read "Rocks from space" and in the end of the book they mention
> Nemesis in the Oort cloud as being a red dwarf with a cycle of 26 to
> 30 million years.

The theory that the sun has a long period, highly eccentric, red dwarf
or brown dwarf companion is based on a ~perceived~ periodicity in
earth's mass extinction record. From a strictly dynamical standpoint,
it is a rather unlikely theory, IMO, since the dwarf orbit's required
semi-major axis is so great that it would be subject to perturbations
by nearby stars. In other words, the orbit would not be stable.

Thanks to WISE (the Wide-field Infrared Survey Explorer), we shall
soon be able to confirm or discard this theory. WISE is sensitive
enough to detect any red dwarf or brown dwarf out to distances
an order of magnitude greater than Nemesis' greatest possible
distance. Even a Jupiter-mass object would be detectable at a
distance of 1 light year, while a three-Jupiter-mass object
would be detectable at 10 light years' distance.

Realistically, if Nemesis exists it is almost certainly not a red
dwarf as it would already have been discovered. A brown dwarf is
the largest realistic candidate, and some Nemesis proponents
theorize that its mass is only 3-5 times that of Jupiter -- too
small to even be categorized as a brown dwarf. (Brown dwarf
minimum size is 13 Jupiter masses -- the minimum mass to fuse
deuterium.)

So far WISE has discovered two unambiguous brown dwarfs (and a
number of brown dwarf candidates), although their distances are
not yet known. Follow-up measurements must be made by other
instruments to measure their parallaxes, but I suspect these
first two are more than 3 light years away (too distant to be
Nemesis candidates).

--Rob
Received on Mon 06 Sep 2010 03:52:15 PM PDT