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Encyclopedia > Oort cloud
Artist's rendering of the Oort cloud and the Kuiper Belt.
Artist's rendering of the Oort cloud and the Kuiper Belt.
Presumed distance of the Oort cloud compared to the rest of the solar system.
Presumed distance of the Oort cloud compared to the rest of the solar system.

The Oort cloud (pronounced /ɔrt/ ort, alternatively the Öpik-Oort Cloud (IPA: [ˈøpɪk]: that is, as [ˈepɪk] with a rounded [e])), is a postulated spherical cloud of comets situated about 50,000 AU[1] from the Sun. This is approximately 1000 times the distance from the Sun to Pluto or nearly a light year. The outer extent of the Oort cloud places the boundary of our Solar System at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun. Image File history File links Kuiper_oort. ... Image File history File links Kuiper_oort. ... The Kuiper belt, derived from data from the Minor Planet Center. ... 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. ... This article is about the Solar System. ... For other uses, see Sphere (disambiguation). ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... 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. ... Sol redirects here. ... Atmospheric characteristics Atmospheric pressure 0. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... Proxima Centauri (Latin proximus, -a, -um: meaning next to or nearest to)[4] is a red dwarf star that is likely a part of the Alpha Centauri star system and is the nearest star to the Sun at a distance of 4. ...


Although no confirmed direct observations of the Oort cloud have been made, astronomers believe it to be the source of all long period and Halley-type comets entering the inner solar system (some short-period comets, based on their orbits, may come from the Kuiper belt).[1] Comet Halley as taken with the Halley Multicolor Camera on the ESA Giotto mission. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... This article is about the Solar System. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... The Kuiper belt, derived from data from the Minor Planet Center. ...

Contents

Hypothesis

In 1932 Ernst Öpik, an Estonian astronomer, proposed[2] that comets originate in an orbiting cloud situated at the outermost edge of the solar system. In 1950 the idea was revived independently[3] by Dutch astronomer Jan Hendrik Oort to explain an apparent contradiction: comets are destroyed by several passes through the inner solar system, yet if the comets we observe had really existed for billions of years (since the origin of the solar system), all would have been destroyed by now. According to the hypothesis, the Oort cloud contains trillions 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. In order for it to supply the necessary volume of comets, the total mass of comets in the Oort cloud must be many times that of Earth. Year 1932 (MCMXXXII) was a leap year starting on Friday (the link will display full 1932 calendar) of the Gregorian calendar. ... Ernst Julius Öpik (October 23, 1893 – September 10, 1985) was a notable Baltic German Estonian astronomer and astrophysicist, who spent the last part of his career (1948–1981) in emigration at the Armagh Observatory in Northern Ireland. ... Year 1950 (MCML) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar. ... Jan Hendrik Oort (April 28, 1900 – November 5, 1992) was an internationally famous Dutch astronomer. ...


Structure and composition

The Oort cloud is thought to occupy a vast space from the outer boundary of the Kuiper belt at 50 AU to as far as 50,000 AU from the Sun. It can be subdivided into spherical outer Oort cloud (20,000-50,000 AU) and doughnut-shaped inner Oort cloud (50-20,000 AU). The outer cloud is only weakly bound to the Sun and supplies the long period (and possibly Halley-type) comets to the inner part of the Solar System.[1] The inner Oort cloud is also known as the Hills cloud, and may be the source of Halley-type comets.[4]. Some scientists think that the Hills cloud may contain much more material than the outer cloud.[5][6] This hypothesis is employed to explain the continued existence of the Oort cloud over the course of billions of years.[7] The Kuiper belt, derived from data from the Minor Planet Center. ... Comet Halley as taken with the Halley Multicolor Camera on the ESA Giotto mission. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... This article is about the Solar System. ... The Hills cloud is a hypothetical inner region of the Oort cloud with an outer boundary of 2-3×104 AU, and a less well defined inner boundary at 50 to 3000 AU, proposed in 1981 by J. G. Hill. ... Comet Halley as taken with the Halley Multicolor Camera on the ESA Giotto mission. ...


The outer Oort cloud is commonly thought to contain several trillion individual comet nuclei larger than ~1.3 km,[1] each tens of millions of kilometers apart.[8] Its mass is not known with certainty, but is unlikely to be more than a few Earth masses[1] [9]. Earlier it was thought to be more massive (up to 380 Earth masses).[10] However, the improved knowledge about the size distribution of the long period comets led to much lower values. The mass of the inner Oort cloud is not currently known.


The vast majority of Oort cloud objects are believed to consist of various ices, but the discovery of the object 1996 PW suggests that it may also be home to rocky objects.[11]


Origin

The Oort cloud is thought to be a remnant of the original protoplanetary disc that formed around the Sun approximately 4.6 billion years ago.[1] Its outer part is only loosely bound to the solar system, and thus easily affected by the motions of passing stars or other forces.[12] A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... The theories concerning the formation and evolution of the Solar System are complex and varied, interweaving various scientific disciplines, from astronomy and physics to geology and planetary science. ...


The most widely-accepted hypothesis 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.[1][13] The current mass of the cloud (about 3 Earth masses) is only a small part of the mass of ejected material (50-100 Earth masses).[1] While on the distant outer regions of these orbits, gravitational interaction with nearby stars and galactical tides further modified their orbits to make them more circular. This explains a near spherical shape of the outer Oort cloud. On the other hand the Hills cloud, being bound more strongly to the Sun, hasn't acquired spherical shape yet. Recent studies have shown that the formation of the Oort cloud is broadly compatible with the hypothesis that the Solar System formed as part of an embedded cluster among between 200 and 400 stars. These early stars likely played a role in the cloud's formation.[14] Sol redirects here. ... This article is about the astronomical term. ... For other uses, see Asteroid (disambiguation). ... 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. ... The Hills cloud is a hypothetical inner region of the Oort cloud with an outer boundary of 2-3×104 AU, and a less well defined inner boundary at 50 to 3000 AU, proposed in 1981 by J. G. Hill. ... This article is about the Solar System. ...


Star perturbations and Nemesis theory

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 perturbations in the comets' orbits and thereby increasing the number of comets that enter the inner solar system. The interactions of the Oort cloud with those of neighboring stars, and its deformation by the galactic tide are thought to be the main triggers which send the long-period comets into the inner Solar System.[1][15] This process also serves to scatter the objects out of the ecliptic plane, explaining the cloud's spherical distribution.[16][17] This article is about the astronomical object. ... The Andromeda Galaxy. ... This article is about the Solar System. ...


The known star with the greatest possibility of perturbing the Oort cloud in the next 10 million years is Gliese 710.[17] However, physicist Richard A. Muller and others have postulated that the Sun has a heretofore undetected companion (brown dwarf or gaseous giant planet) in an elliptical orbit beyond the Oort cloud. This object, known as Nemesis, is theorized to pass through a portion of the Oort cloud approximately every 26 million years, bombarding the inner solar system with comets. Although the theory has many proponents, no direct proof of the existence of Nemesis has been found.[18] Furthermore, many argue that a companion star at such a great distance could not have a stable orbit, as it would probably be ejected by perturbations from other stars. Gliese 710 is a red dwarf star in the constellation Serpens Cauda, with visual magnitude 9. ... Richard Muller Richard A. Muller (January 6, 1944 -) of San Francisco, California, USA, is a physicist who works at the University of California, Berkeley and Lawrence Berkeley National Laboratory. ... Sol redirects here. ... This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. ... Nemesis is a hypothetical red dwarf star or brown dwarf, orbiting the Sun at a distance of about 50,000 to 100,000 AU, somewhat beyond the Oort cloud. ... This article is about the Solar System. ...


Oort cloud objects (OCO)

TNOs and similar bodies

So far, only two objects with orbits which suggest that they may belong to the Oort Cloud have been discovered: 90377 Sedna and 2000 CR105. Unlike scattered disk objects, their orbits cannot be explained by perturbations of the main known planets and may thus belong to the inner Oort cloud. Their orbits can then be explained by one of two theories. Either these objects were Oort cloud bodies disrupted by the passage of a nearby star close to the solar system,[19] or else their orbits were disrupted by an as-yet-unknown planet-sized body within the Oort Cloud.[20] The centaurs are a class of icy planetoids that orbit the Sun between Jupiter and Neptune, named after the mythical race of centaurs. ... As of March 2007, there are five[1] known Neptune Trojans (named by analogy to the Trojan asteroids) which have the same orbital period as the planet. ... A trans-Neptunian object (TNO) is any object in the solar system that orbits the sun at a greater distance on average than Neptune. ... The Kuiper belt, derived from data from the Minor Planet Center. ... In astronomy a cubewano (pronounced ) is a Kuiper belt object that orbits beyond Neptune and is not controlled by an orbital resonance with the giant planet. ... In astronomy, a resonant Trans-Neptunian Object is a Trans-Neptunian Object (TNO) in mean motion orbital resonance with Neptune. ... In astronomy, a plutino is a trans-Neptunian object that has a 3:2 orbital resonance with Neptune. ... Eris, the largest known scattered disc object (center), and its moon Dysnomia (left of center). ... you are abunch of bull | bgcolour=#FFFFC0 | name=90377 Sedna | image= | caption= Sedna is located in the center of the green circle | discovery=yes | discoverer=M. Brown, C. Trujillo, D. Rabinowitz | discovered=November 14, 2003 | mp_name=90377 Sedna | alt_names= | mp_category=Trans-Neptunian object | epoch=September 26, 1990 (JD 2448160. ... 2000 CR105 is the third most distant known object in the solar system after 2003 UB313 and 90377 Sedna. ...

Oort cloud object candidates
Number Name Equatorial diameter
(km)
Perihelion (AU) Aphelion (AU) Year discovered Discoverer Diameter method
90377 Sedna 1180 - 1800 km 76.1 892 2003 Brown, Trujillo, Rabinowitz thermal
148209 2000 CR105 265 km 44.3 397 2000 Lowell Observatory  ???

A diagram of Keplerian orbital elements. ... A diagram of Keplerian orbital elements. ... you are abunch of bull | bgcolour=#FFFFC0 | name=90377 Sedna | image= | caption= Sedna is located in the center of the green circle | discovery=yes | discoverer=M. Brown, C. Trujillo, D. Rabinowitz | discovered=November 14, 2003 | mp_name=90377 Sedna | alt_names= | mp_category=Trans-Neptunian object | epoch=September 26, 1990 (JD 2448160. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... Michael (Mike) E. Brown (born c. ... Chadwick A. Chad Trujillo (born November 22, 1973), is the co-discoverer of Eris, which he claims to be the Tenth Planet. ... This article or section does not cite its references or sources. ... 2000 CR105 is the third most distant known object in the solar system after 2003 UB313 and 90377 Sedna. ... Year 2000 (MM) was a leap year starting on Saturday (link will display full 2000 Gregorian calendar). ... Lowell Observatory Percival observing Mars from the Clark telescope at the Lowell Observatory. ...

See also

This article is about the Solar System. ... The Andromeda Galaxy. ...

References

  1. ^ a b c d e f g h i Alessandro Morbidelli (2006). Origin and dynamical evolution of comets and their reservoirs. Retrieved on 2007-05-26.
  2. ^ Öpik, E., Note on Stellar Perturbations of Nearby Parabolic Orbits, Proceedings of the American Academy of Arts and Sciences, Vol. 67, pp. 169-182 (1932)
  3. ^ Oort, J. H., The structure of the cloud of comets surrounding the Solar System and a hypothesis concerning its origin, Bull. Astron. Inst. Neth., 11, p. 91-110 (1950) Text at Harvard server (PDF)
  4. ^ Harold F. Levison, Luke Dones, Martin J. Duncan (2001). The Origin of Halley-Type Comets: Probing the Inner Oort Cloud. Retrieved on 2007-06-27.
  5. ^ Hills, J. G. (November 1981). "Comet showers and the steady-state infall of comets from the Oort cloud". Astronomical Journal 86: 1730-1740. doi:10.1086/113058. 
  6. ^ Planetary Sciences: American and Soviet Research, Proceedings from the U.S.-U.S.S.R. Workshop on Planetary Sciences, 1991, p. 251
  7. ^ Julio A. Ferna´ndez (1996). The Formation of the Oort Cloud and the Primitive Galactic Environment. Departamento de Astronomı´a, Facultad de Ciencias, Tristan Narvaja. Retrieved on 2007-05-26.
  8. ^ PAUL R. WEISSMAN (1998). The Oort Cloud. Scientific American. Retrieved on 2007-05-26.
  9. ^ PR Weissman (1981). The mass of the Oort cloud. California Institute of Technology. Retrieved on 2007-05-26.
  10. ^ (meteorobs) Excerpts from "CCNet 19/2001 (2001). Retrieved on 2007-05-26.
  11. ^ PAUL R. WEISSMAN, HAROLD F. LEVISON (1997). Origin and Evolution of the Unusual Object 1996 PW: Asteroids from the Oort Cloud?. Earth and Space Sciences Division, Jet Propulsion Laboratory, Space Sciences Department, Southwest Research Institute. Retrieved on 2007-05-26.
  12. ^ The Oort cloud. Retrieved on 2007-05-26.
  13. ^ Oort Cloud & Sol b?. SolStation. Retrieved on 2007-05-26.
  14. ^ R. Brasser, M. J. Duncan, H.F. Levison (2006). Embedded star clusters and the formation of the Oort Cloud. Retrieved on 2007-05-26.
  15. ^ Rosanna L. Hamilton (1999). The Oort Cloud. Retrieved on 2007-05-26.
  16. ^ A. Higuchi, E. Kokubo (2006). Evolution of the Oort Cloud and Distribution of New Comets Due to the Galactic Tide. National Astronomical Observatory of Japan. Retrieved on 2007-05-27.
  17. ^ a b L. A. Molnar, R. L. Mutel. Close Approaches of Stars to the Oort Cloud: Algol and Gliese 710. University of Iowwa. Retrieved on 2007-05-27.
  18. ^ J. G. Hills (1984). Dynamical constraints on the mass and perihelion distance of Nemesis and the stability of its orbit. Nature. Retrieved on 2006-06-23.
  19. ^ Morbidelli, Alessandro; Harold Levison (2004). "Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR105 and 2003 VB12 (Sedna)". Astron. J. 128: 2564-2576. 
  20. ^ Gomes, Rodney S.; John J. Matese, and Jack J. Lissauer (2006). "A distant planetary-mass solar companion may have produced distant detached objects". Icarus 184: 589-601. 

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... 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. ... Jan Hendrik Oort (April 28, 1900 – November 5, 1992) was an internationally famous Dutch astronomer. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 178th day of the year (179th in leap years) in the Gregorian calendar. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 146th day of the year (147th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 147th day of the year (148th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 147th day of the year (148th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 174th day of the year (175th in leap years) in the Gregorian calendar. ...

External links

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Planets · Dwarf planets · Moons: Terrestrial · Martian · Jovian · Saturnian · Uranian · Neptunian · Plutonian · Eridian
Small bodies:   Meteoroids · Asteroids/Asteroid moons (Asteroid belt) · Centaurs · TNOs (Kuiper belt/Scattered disc) · Comets (Oort cloud)
See also astronomical objects, the solar system's list of objects, sorted by radius or mass, and the Solar System Portal

  Results from FactBites:
 
Oort Cloud (719 words)
The Oort cloud is an immense spherical cloud surrounding the planetary system and extending approximately 3 light years, about 30 trillion kilometers from the Sun.
The structure of the cloud is believed to consist of a relatively dense core that lies near the ecliptic plane and gradually replenishes the outer boundaries, creating a steady state.
The Oort cloud is the source of long-period comets and possibly higher-inclination intermediate comets that were pulled into shorter period orbits by the planets, such as Halley and Swift-Tuttle.
Oort cloud (240 words)
The Oort cloud was proposed in 1950 by Dutch astronomer Jan 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.
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.
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.
  More results at FactBites »

 
 

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