Astrophysics (Index)About

Oort Cloud

(Öpik-Oort Cloud)
(cloud of comets and minor planets around the solar system)

The Oort Cloud (aka Öpik-Oort Cloud) is a theorized cloud of minor planets and comets at a distance from around 2,000 to possibly 200,000 AU (about 3 light-years, 3/4 the distance to Alpha Centauri) from the Sun. It is the source of long-period comets, those with an extremely elliptical orbit and a distant aphelion (the orbit's far point of the Sun) in the above-given range, and orbiting on random planes rather than somewhat near the ecliptic. These comets are thought to generally remain at a distance and assume orbits traversing the inner solar system only when disturbed.

The Oort Cloud concept grew from a need to explain the orbital inclination of these comets, the fact that the orbits appear unstable, i.e., incapable of lasting billions of years, and that such comet bodies would not survive the repeated sweeps nearing the Sun.

(minor planets,comets,solar system)
Further reading:

Referenced by pages:
galactic tide
Hills cloud
Kuiper Belt (K Belt)
long-period comet
Nice model
solar system