At first a little astronomy from Wikipedia.
Nemesis is a hypothetical red dwarf star or brown dwarf, orbiting the Sun at a distance of about 50,000 to 100,000 AU, somewhat beyond the Oort cloud. Richard A. Muller suggests that the most likely object is a red dwarf with magnitude between 7 and 12.
According to the hypothesis, Nemesis periodically (roughly every 26 million years) passes through a denser region of the Oort cloud, disrupting the orbits of comets, and sending millions of comets into the inner solar system and potential collision with the Earth. The last major extinction period was about 5 million years ago, so Muller posits that Nemesis is likely 1-1.5 light years away at present, and even has ideas of what area of the sky it might be in (supported by Yarris, 1987), near Hydra, based on a theoretical orbit derived from original apogees of a number of atypical long period comets that describe an orbital arc meeting the specifications of Muller's theory. It was initially nicknamed the "death star", after the fictional Star Wars weapon, although this nickname has fallen out of usage.
No direct proof of the existence of Nemesis has been found, however, and the existence of a periodicity in the Earth's series of mass extinctions is disputed. Muller has proposed that, based on analysis of lunar rocks that indicate the impact history of the Moon, a major uptick in lunar impacts 400 million years ago (mya) represents a major shift in the orbit of Nemesis into its present rather eccentric orbit, which according to Piet Hut will only be stable for another billion years.
Now you know what is Nemesis. Would you like to create a Nemesis model for the Solar System? It's easy .
Create a .ssc file with this informations
"Nemesis" "Sol"
{
Texture "browndwarf.jpg"
Radius 50000
Emissive true
Color [ 1 0.5 0.5 ]
EllipticalOrbit {
Period 200000
SemiMajorAxis 40000
Eccentricity 0.437
Inclination 06.18
AscendingNode 133.51
ArgOfPericenter 256.42
MeanAnomaly 241.70
}
RotationPeriod 20
}
http://img105.imageshack.us/my.php?image=nemesisdv6.jpg
Remember that the file is not accurated 100% and has fictional infos .