The Oort limit is a theoretical location at the outer limits of the

Oort cloud The Oort cloud (), sometimes called the Öpik–Oort cloud, first described in 1950 by the Dutch astronomer Jan Oort, is a theoretical concept of a cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from 2 ...

, where the amount of comets and minor planets orbiting the Sun drops drastically, or drops entirely. The exact location of such a limit, if there is such one, is uncertain. About 100 comets, of 3500 known comets, come more than 5000 AU from the Sun, and a very few come as far as 20,000 AU from the Sun. So far, it appears that rather than a sudden drop in the amount of comets orbiting the sun at about 50,000 AU, the Oort cloud rather uniformly decreases in size, the further away from the Sun it goes. As current observations indicate, the Oort limit is somewhere around 50,000 AU (0.8 LY) from the Sun.

Notes

{{note, 1 Of these known comets, the majority (>2000) were discovered using the

SOHO Soho is an area of the City of Westminster, part of the West End of London. Originally a fashionable district for the aristocracy, it has been one of the main entertainment districts in the capital since the 19th century. The area was develop ...

telescope, and are mostly sungrazing comets from the

Kreutz Sungrazers The Kreutz sungrazers ( ) are a family of sungrazing comets, characterized by orbits taking them extremely close to the Sun at perihelion. They are believed to be fragments of one large comet that broke up several centuries ago and are named for G ...

. Of the other comets, about half of them are long-period comets, orbiting several hundred Astronomical Units out or further. Considering this, Oort Cloud comets are fairly common.

References

The Encyclopedia of Astrobiology, Astronomy, and Spaceflight
Oort cloud Trans-Neptunian region Jan Oort

Notes

See also

References