Oort cloud

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Related to Oort cloud: Kuiper belt, Sedna

Oort cloud:

see cometcomet
[Gr.,=longhaired], a small celestial body consisting mostly of dust and gases that moves in an elongated elliptical or nearly parabolic orbit around the sun or another star. Comets visible from the earth can be seen for periods ranging from a few days to several months.
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Oort cloud

(oort, ort) (Öpik–Oort cloud) A cloud of comets that move in orbits round the Sun with perihelia in the range 5–50 AU and aphelia in a zone with heliocentric distances between 30 000 and 100 000 AU, i.e. in a zone far beyond Pluto's orbit. Since the nearest star to the Sun – Proxima Centauri – is 270 000 AU away these comets can be perturbed by passing stars; this changes their orbits and send them in closer toward our Sun (or out toward the perturbing star). These perturbed comets have periods of hundreds of thousands of years. The Oort cloud is so distant that it acts as a refrigerated cometary reservoir.

The existence of a distant long-lived cloud of comets was first suggested in 1932 by Ernst Öpik. The same idea was proposed in 1950 by J.H. Oort who thought that comets originated from the disintegration of a planet some time in the early history of the Solar System. After this the major planets, Jupiter in particular, drove the majority of the comets either into the inner Solar System, where they decayed, or into the outer regions. Of this latter group 98% would have been lost from the Solar System, only 2% remaining in the Oort cloud. The number of comets in the cloud is uncertain but it could be somewhere in the range 1011 to 1012 with a total mass in the region of 1028 grams. The orbits are oriented at random. A cometary cloud of radius 100 000 AU has a half life of at least 1.1 × 109 years. The existence of the cloud shows up very clearly when the number distribution of comets is considered as a function of the reciprocal of the semimajor axes of the orbits. See also Kuiper belt.

References in periodicals archive ?
Its fraction of heavy water is three times that of Earth, higher than those of the Oort cloud comets.
Astro Lords: Oort Cloud, a massively multiplayer strategy game, was presented as a beta on Game Connection Europe and Indie Prize Showcase Amsterdam 2014 game contests.
While many comets come out of the Oort cloud and return after a long trip through the solar system and many comets graze by the sun, this is the first one that astronomers have watched that is from the Oort cloud and is skimming the sun.
This particular comet is thought to have its origins in the Oort Cloud with aphelion at 63,600 AU, but after its passage through the inner solar system, would have been perturbed by planetary encounters into an 11,800 year orbit with a semi-major axis of 518 AU.
Jexper's composition Oort Cloud, a piece which premiered at Huddersfield Contemporary Music Festival last year, was inspired by the patterns of icy debris in dying solar systems.
They now make up much of the Oort Cloud, the roughly spherical cloud of comets that surrounds the Sun extending halfway to the nearest star, say the scientists.
They modelled what would happen to dust released from various sources--asteroid collisions, comets arriving on random orbits from the Oort Cloud, and especially "Jupiter-family comets" (orbital periods of less than 20 years)--and kept track of what went where.
In addition, the outer reaches of our solar system have been divided into three regions: the Kuiper Belt, the Scattered Disc and the Oort Cloud.
The buckets--the large is named Sedna after the newest, farthest and coldest planet (discovered in 2003), and the smaller one Oort, after the Oort cloud in outer space--retail from $50 to $70 and come in two styles: brown with orange interior and slate with glacier interior.
Even farther out is the Oort cloud, a region of comets and, perhaps, still more planet-like objects.
They are believed to originate from the Oort Cloud, named after the Dutch astronomer, Jan Oort.
It touches on the Oort Cloud, and ventures into the more recent theories of the influence of large meteorite impacts on the development of life on Earth.