Hi Rob, Great answer to a question I had about it. How does one
determine the cycle of a star?
Also, if the Nemesis companion star does not exist for our Sun, are
there any other theories or explanations of comets and how their orbits
are perturbed into our system? What causes these bodies from the Oort
cloud to be pulled into our solar system if not by a large mass such as
another star? Do they simply bump into one another as is evidenced by
Asteroid P/2010 A2
http://www.nasa.gov/mission_pages/hubble/science/asteroid-20100202.html
In my understanding of comets they are originally stony/icy bodies that
dwell originate from within the Kuiper Belt and Oort cloud which
surrounds our solar system. We just don't call them comets until they
come into our system of course and their "tails" are formed and become
visible to us. The IAU defines them as a "Small Solar System body"
according to Wikipedia.
Question... Are asteroids (within the asteroid belt) dead comets? Or
just simply debris left over from the formation of the solar system from
the protoplanetary disk?
There was an article in the March 2010 issue of Sky & Telescope titled
"What else is out there?" by David Jewitt (Professor of Planetary
Science at the UCLA) that makes a brief mention of Nemisis.
http://www2.ess.ucla.edu/~jewitt/papers/2010/J10b.pdf but also explains
the likelihood of seeing the brown dwarf at such vast distances. It also
mentions WISE. To see a brown dwarf star is very difficult optically,
but it would be much brighter in the infrared spectrum and easier to
see. Perhaps WISE will find the companion star if in fact it exists?
The thought experiment of visualizing Earth at KBO distances and beyond
is thought provoking and puts things into a very intriguing perspective.
I find this extremely fascinating!
Regards,
Eric
On 9/6/2010 12:52 PM, Rob Matson wrote:
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
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