an exercise in miscellany

Nemesis

In science & nature, wild card on August 24, 2011 at 9:17 am

Nemesis is a hypothetical hard-to-detect red dwarf star, white dwarf star or brown dwarf, orbiting the Sun at a distance of about 50,000 to 100,000 AU (about 0.8-1.5 light-years), somewhat beyond the Oort cloud.This star was originally postulated to exist as part of a hypothesis to explain a perceived cycle of mass extinctions in the geological record, which seem to occur once every 26 million years or so. In addition, observations by astronomers of the sharp edges of Oort clouds, similar to that of the Solar System, around various binary (double) star systems, in contrast to the diffuse edges of the Oort clouds around single-star systems, has prompted some scientists to postulate that a dwarf star may be co-orbiting the Sun. Counter-theories also exist that other forces (like the angular effect of the galactic gravity plane) may be the cause of the sharp-edged Oort cloud pattern around the Sun. To date the issue remains unsettled in the scientific community.

via Nemesis (hypothetical star)

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