This diagram shows the presumed distance of the Oort cloud compared to the rest of the solar system.

The Oort cloud (sometimes called the Öpik-Oort Cloud) is a postulated spherical cloud of comets situated about 50,000 to 100,000 AU from the Sun. This is approximately 1000 times the distance from the Sun to Pluto or roughly one light year, almost a quarter of the distance from the Sun to Proxima Centauri, the star nearest the Sun. This NASA diagram demonstrates the presumed distance of the Oort cloud compared to the solar systems planets, the Kuiper belt, and the 90377 Sedna planetoid. ... This NASA diagram demonstrates the presumed distance of the Oort cloud compared to the solar systems planets, the Kuiper belt, and the 90377 Sedna planetoid. ... Mosaic of Solar System planets except Pluto, including Earths Moon (not to scale). ... A sphere is, roughly speaking, a ball-shaped object. ... Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) A comet is a small astronomical object similar to an asteroid but composed largely of ice. ... To help compare different distances this page lists lengths starting at 1015 m (1,000,000 million km). ... To help compare different distances this page lists lengths starting at 1016 m (67,000 AU, 1. ... The astronomical unit (AU or au or a. ... A sun is the star at the center of a planetary system. ... Atmospheric characteristics Atmospheric pressure 0. ... A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ... The red dwarf star Proxima Centauri, part of the Alpha Centauri star system, is the nearest star to Earth, other than the Sun. ...

The Oort cloud would have its inner disk at the ecliptic from the Kuiper belt. Although no direct observations have been made of such a cloud, it is believed to be the source of most or all comets entering the inner solar system (some short-period comets may come from the Kuiper belt), based on observations of the orbits of comets. The Kuiper belt (KYE per) is an area of the solar system extending from within the orbit of Neptune (at 30 AU) to 50 AU from the sun, at inclinations consistent with the ecliptic. ... Mosaic of Solar System planets except Pluto, including Earths Moon (not to scale). ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ...

In 1932 Ernst Öpik, an Estonian astronomer, proposed that comets originate in an orbiting cloud situated at the outermost edge of the solar system. In 1950 the idea was revived and proposed by Dutch astronomer Jan Hendrick Oort to explain an apparent contradiction: comets are destroyed by several passes through the inner solar system, yet if the comets we observe had existed since the origin of the solar system, all would have been destroyed by now. According to the theory, the Oort cloud contains millions of comet nuclei, which are stable because the sun's radiation is very weak at their distance. The cloud provides a continual supply of new comets, replacing those that are destroyed. It is believed that the total mass of comets in the Oort cloud is many times that of Earth, and estimates range between five and 100 Earth masses. 1932 is a leap year starting on a Friday. ... Ernst Julius Öpik Ernst Julius Öpik (October 23, 1893 – September 10, 1985) was a notable Estonian astronomer and astrophysicist, who spent the last part of his career (1948–1981) at the Armagh Observatory in Northern Ireland. ... 1950 was a common year starting on Sunday (link will take you to calendar). ... Jan Hendrik Oort (April 28, 1900 – November 5, 1992) was an internationally famous Dutch astronomer. ...

The Oort cloud is a remnant of the original nebula that collapsed to form the Sun and planets five billion years ago, and is loosely bound to the solar system. The most widely-accepted theory of its formation is that the Oort cloud's objects initially formed much closer to the Sun as part of the same process that formed the planets and asteroids, but that gravitational interaction with young gas giants such as Jupiter ejected them into extremely long elliptical or parabolic orbits. This process also served to scatter the objects out of the ecliptic plane, explaining the cloud's spherical distribution. While on the distant outer regions of these orbits, gravitational interaction with nearby stars further modified their orbits to make them more circular. The Triangulum Emission Nebula NGC 604 lies in a spiral arm of Galaxy M33, 2. ... A planet (from the Greek πλανήτης, planētēs which means wanderer or more forcefully vagrant, tramp) is an object in orbit around a star that is not a star in its own right. ... It has been suggested that Timeline of the Big Bang be merged into this article or section. ... A sun is the star at the center of a planetary system. ... A planet (from the Greek πλανήτης, planētēs which means wanderer or more forcefully vagrant, tramp) is an object in orbit around a star that is not a star in its own right. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... In astrodynamics or celestial mechanics a elliptic orbit is an orbit with the eccentricity greater than 0 and less than 1. ... In astrodynamics or celestial mechanics a parabolic trajectory is an orbit with the eccentricity equal to 1. ...

It is thought that other stars are likely to possess Oort clouds of their own, and that the outer edges of two nearby stars' Oort clouds may sometimes overlap, causing the occasional intrusion of a comet into the inner solar system. The star with the greatest possibility of perturbing the Oort cloud in the next 10 million years is Gliese 710. The Pleiades star cluster A star is any massive gaseous body in outer space, just like the Sun. ... Gliese 710 is a red dwarf star in the constellation Serpens Cauda, with visual magnitude 9. ...

Oort cloud objects

So far, only one potential Oort cloud object has been discovered; 90377 Sedna. With an orbit that ranges from roughly 76 to 928 AU, it is much closer than originally expected and may belong to an "inner" Oort cloud. If Sedna indeed belongs to the Oort cloud, this may mean that the Oort cloud is both denser and closer to the Sun than previously thought. This has been proposed as possible evidence that the Sun initially formed as part of a dense cluster of stars; with closer neighbors during Oort cloud formation, objects ejected by gas giants would have their orbits circularized closer to the Sun than was predicted for situations with more distant neighbors. The centaurs are a class of icy planetoids that orbit the Sun between Jupiter and Neptune, named after the mythical race of centaurs. ... A trans-Neptunian object (TNO) is any object in the solar system with all or most of its orbit beyond that of Neptune. ... The Kuiper belt (KYE per) is an area of the solar system extending from within the orbit of Neptune (at 30 AU) to 50 AU from the sun, at inclinations consistent with the ecliptic. ... In astronomy, a plutino is a Pluto-like object, insofar as it has the same relative orbit as Pluto. ... A cubewano is any substantial Kuiper belt object, orbiting beyond about 41 AU and not controlled by resonances with the outer planets. ... A scattered disk object (or scattered disc object or SDO) is a trans-Neptunian object of the Kuiper belt with a very eccentric orbit. ... 90377 Sedna is a trans-Neptunian object, discovered by Mike Brown (Caltech), Chad Trujillo (Gemini Observatory) and David L. Rabinowitz (Yale University) on November 14, 2003. ...

elements of an orbit In astronomy, an apsis (plural apsides ap-si-deez) is the point of greatest or least distance of the elliptical orbit of a celestial body from its center of attraction (the center of mass of the system). ... elements of an orbit In astronomy, an apsis (plural apsides ap-si-deez) is the point of greatest or least distance of the elliptical orbit of a celestial body from its center of attraction (the center of mass of the system). ... 90377 Sedna is a trans-Neptunian object, discovered by Mike Brown (Caltech), Chad Trujillo (Gemini Observatory) and David L. Rabinowitz (Yale University) on November 14, 2003. ... 2003 is a common year starting on Wednesday of the Gregorian calendar. ... Michael (Mike) E. Brown has been an associate professor of planetary astronomy at the California Institute of Technology (Caltech) since 2002. ... Chadwick A. Trujillo (born November 22, 1973) is a postdoctoral scholar at Caltech researching the Edgeworth-Kuiper belt and the outer solar system. ... David L. Rabinowitz (born 1960) is a professor at Yale University researching the Kuiper belt and the outer solar system. ...

External links

• Representation, Southwest Research Institute
• The Kuiper Belt and The Oort Cloud

Minor planet is the official term for asteroids and trans-Neptunian objects. ... Vulcanoids are hypothetical asteroids that may orbit in a dynamically stable zone between 0. ... The asteroid belt is a region of the solar system falling roughly between the planets Mars and Jupiter where the greatest concentration of asteroid orbits can be found. ... Near-Earth objects (NEO) are asteroids, comets and large meteoroids whose orbit intersects Earths orbit and which may therefore pose a collision danger. ... As originally defined, Trojan asteroids have a semi-major axis between 5. ... The centaurs are a class of icy planetoids that orbit the Sun between Jupiter and Neptune, named after the mythical race of centaurs. ... A trans-Neptunian object (TNO) is any object in the solar system with all or most of its orbit beyond that of Neptune. ... Damocloids are asteroids such as 5335 Damocles and (16746) 1996 PW that have long-period highly eccentric orbits typical of periodic comets such as 1P/Halley, but without showing a cometary coma or tail. ... Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) A comet is a small astronomical object similar to an asteroid but composed largely of ice. ... The Kuiper belt (KYE per) is an area of the solar system extending from within the orbit of Neptune (at 30 AU) to 50 AU from the sun, at inclinations consistent with the ecliptic. ... An asteroid moon is an asteroid that orbits another asteroid. ... Mosaic of Solar System planets except Pluto, including Earths Moon (not to scale). ... This is a list of numbered asteroids, in sequential order. ... This page alphabetically lists the first thousand asteroids to be numbered, which are mostly in the main belt. ...