118401 LINEAR
Encyclopedia
118401 LINEAR is an asteroid
and main-belt comet
(176P/LINEAR) which was discovered by the Lincoln Near-Earth Asteroid Research
(LINEAR) 1-metre telescopes in Socorro, New Mexico
on September 7, 1999. (118401) LINEAR was discovered to be cometary on November 26, 2005, by Henry H. Hsieh and David C. Jewitt
as part of the Hawaii Trails project using the Gemini North 8-m telescope on Mauna Kea
and was confirmed by the University of Hawaii
's 2.2-m (88-in) telescope on December 24–27, 2005, and Gemini on December 29, 2005. The Spitzer Space Telescope
has estimated (118401) LINEAR to be 4.0±0.4 km in diameter.
The main-belt comets are unique in that they have flat (within the plane of the planets' orbits), approximately circular (small eccentricity
), asteroid
-like orbit
s, and not the elongated, often tilted orbits characteristic of all other comets. Since (118401) LINEAR can generate a coma
(produced by vapour boiled off the comet), it must be an icy asteroid. When a typical comet approaches the Sun
, its ice
heats up and sublimates (changes directly from ice to gas
), venting gas and dust
into space
, creating a tail and giving the object a fuzzy appearance. Far from the Sun, sublimation stops, and the remaining ice stays frozen until the comet's next pass close to the Sun. In contrast, objects in the asteroid belt have essentially circular orbits and are expected to be mostly baked dry of ice by their confinement to the inner solar system.
It is suggested that these main-belt asteroid-comets are evidence of a recent impact exposing an icy interior to solar radiation. A good question is, "How long will current main-belt comets keep generating a coma?" It is estimated short-period comets remain active for about 10,000 years before having most of their ice sublimated away and going dormant.
Four other objects are classified as both periodic comets and numbered asteroids: 2060 Chiron
(95P/Chiron), 4015 Wilson-Harrington (107P/Wilson-Harrington), 7968 Elst-Pizarro (133P/Elst-Pizarro), and 60558 Echeclus
(174P/Echeclus). As a dual-status object, astrometric observations of 118401 LINEAR should be reported under the minor planet designation.
118401 LINEAR will come to perihelion
on 2011 July 2.
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
and main-belt comet
Main-belt comet
Main-belt comets are bodies orbiting within the main asteroid belt which have shown cometary activity during part of their orbit. The Jet Propulsion Laboratory defines a main-belt asteroid as an asteroid with a semi-major axis of more than 2 AU but less than 3.2 AU, and a perihelion of no less...
(176P/LINEAR) which was discovered by the Lincoln Near-Earth Asteroid Research
Lincoln Near-Earth Asteroid Research
The Lincoln Near-Earth Asteroid Research project is a cooperative project between the United States Air Force, NASA, and MIT's Lincoln Laboratory for the systematic discovery and tracking of near-Earth asteroids. LINEAR was responsible for the majority of asteroid detections since 1998 until...
(LINEAR) 1-metre telescopes in Socorro, New Mexico
Socorro, New Mexico
Socorro is a city in Socorro County in the U.S. state of New Mexico. It stands in the Rio Grande Valley at an elevation of . The population was 9,051 at the 2010 census...
on September 7, 1999. (118401) LINEAR was discovered to be cometary on November 26, 2005, by Henry H. Hsieh and David C. Jewitt
David C. Jewitt
David C. Jewitt is a professor of astronomy formerly at the University of Hawaii Institute for Astronomy, now at UCLA. He was born in 1958 in England, and is a 1979 graduate of the University of London. Jewitt received an M.Sc. and a Ph.D. in astronomy at the California Institute of Technology in...
as part of the Hawaii Trails project using the Gemini North 8-m telescope on Mauna Kea
Mauna Kea
Mauna Kea is a volcano on the island of Hawaii. Standing above sea level, its peak is the highest point in the state of Hawaii. However, much of the mountain is under water; when measured from its oceanic base, Mauna Kea is over tall—significantly taller than Mount Everest...
and was confirmed by the University of Hawaii
University of Hawaii
The University of Hawaii System, formally the University of Hawaii and popularly known as UH, is a public, co-educational college and university system that confers associate, bachelor, master, and doctoral degrees through three university campuses, seven community college campuses, an employment...
's 2.2-m (88-in) telescope on December 24–27, 2005, and Gemini on December 29, 2005. The Spitzer Space Telescope
Spitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
has estimated (118401) LINEAR to be 4.0±0.4 km in diameter.
The main-belt comets are unique in that they have flat (within the plane of the planets' orbits), approximately circular (small eccentricity
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
), asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
-like orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
s, and not the elongated, often tilted orbits characteristic of all other comets. Since (118401) LINEAR can generate a coma
Coma (cometary)
frame|right|The [[153P/Ikeya-Zhang|comet Ikeya-Zhang]] exhibiting a bright, condensed coma In astronomy, a coma is the nebulous envelope around the nucleus of a comet. It is formed when the comet passes close to the Sun on its highly elliptical orbit; as the comet warms, parts of it sublimate...
(produced by vapour boiled off the comet), it must be an icy asteroid. When a typical comet approaches the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, its ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
heats up and sublimates (changes directly from ice to gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
), venting gas and dust
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...
into space
Space
Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum...
, creating a tail and giving the object a fuzzy appearance. Far from the Sun, sublimation stops, and the remaining ice stays frozen until the comet's next pass close to the Sun. In contrast, objects in the asteroid belt have essentially circular orbits and are expected to be mostly baked dry of ice by their confinement to the inner solar system.
It is suggested that these main-belt asteroid-comets are evidence of a recent impact exposing an icy interior to solar radiation. A good question is, "How long will current main-belt comets keep generating a coma?" It is estimated short-period comets remain active for about 10,000 years before having most of their ice sublimated away and going dormant.
Four other objects are classified as both periodic comets and numbered asteroids: 2060 Chiron
2060 Chiron
2060 Chiron is a minor planet in the outer Solar System. Discovered in 1977 by Charles T. Kowal , it was the first-known member of a new class of objects now known as centaurs, with an orbit between Saturn and Uranus.Although it was initially classified as an asteroid, it was later found to...
(95P/Chiron), 4015 Wilson-Harrington (107P/Wilson-Harrington), 7968 Elst-Pizarro (133P/Elst-Pizarro), and 60558 Echeclus
60558 Echeclus
60558 Echeclus is a centaur in the outer Solar System. It was discovered by Spacewatch in 2000 and initially classified as an asteroid with provisional designation . Research in 2001 by Rousselot and Petit at the Besançon observatory in France showed no evidence of cometary activity, but in late...
(174P/Echeclus). As a dual-status object, astrometric observations of 118401 LINEAR should be reported under the minor planet designation.
118401 LINEAR will come to perihelion
Apsis
An apsis , plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system...
on 2011 July 2.
External links
- Orbital simulation from JPL (Java) / Horizons Ephemeris
- 118401 on November 13, 2011
- LINEAR home page
- Seiichi Yoshida's comet list
- New Class of Comets
