118401 LINEAR (
provisional designation , comet designation 176P/LINEAR) is an
active asteroid and
main-belt comet
Active asteroids are Small Solar System body, small Solar System bodies that have asteroid-like orbits but show comet-like visual characteristics. That is, they show a Coma (cometary), coma, comet tail, tail, or other visual evidence of mass-loss ...
[(older 2010 site)]
that was discovered by the
Lincoln Near-Earth Asteroid Research
The Lincoln Near-Earth Asteroid Research (LINEAR) project is a collaboration of the United States Air Force, NASA, and the Massachusetts Institute of Technology's Lincoln Laboratory for the systematic detection and tracking of near-Earth object ...
(LINEAR) 1-metre telescopes in
Socorro, New Mexico
Socorro (, ''Help:Pronunciation respelling key, sə-KOR-oh'') is a city in Socorro County, New Mexico, Socorro County in the U.S. state of New Mexico. It is in the Middle Rio Grande Valley AVA, Rio Grande Valley at an elevation of . At the 2020 ...
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
Mauna Kea (, ; abbreviation for ''Mauna a Wākea''); is a dormant Shield volcano, shield volcano on the Hawaii (island), island of Hawaii. Its peak is above sea level, making it the List of U.S. states by elevation, highest point in Hawaii a ...
and was confirmed by the
University of Hawaii
A university () is an educational institution, institution of tertiary education and research which awards academic degrees in several Discipline (academia), academic disciplines. ''University'' is derived from the Latin phrase , which roughly ...
's 2.2-m (88-in) telescope on December 24–27, 2005, and Gemini on December 29, 2005. Observations using the
Spitzer Space Telescope
The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicate ...
have resulted in an estimate of 4.0±0.4 km for the diameter of (118401) LINEAR.
[
The main-belt comets are unique in that they have flat (within the plane of the planets' orbits), approximately circular (small ]eccentricity
Eccentricity or eccentric may refer to:
* Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal"
Mathematics, science and technology Mathematics
* Off-Centre (geometry), center, in geometry
* Eccentricity (g ...
), asteroid
An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
-like orbit
In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...
s, and not the elongated, often tilted orbits characteristic of all other comets. Because (118401) LINEAR can generate a coma
A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to Nociception, respond normally to Pain, painful stimuli, light, or sound, lacks a normal Circadian rhythm, sleep-wake cycle and does not initiate ...
(produced by vapour boiled off the comet), it must be an icy asteroid. When a typical comet approaches the Sun
The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
, its ice
Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally oc ...
heats up and sublimates (changes directly from ice to gas), venting gas and dust
Dust is made of particle size, fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian processes, aeolian process), Types of volcan ...
into space
Space is a three-dimensional continuum containing positions and directions. In classical physics, physical space is often conceived in three linear dimensions. Modern physicists usually consider it, with time, to be part of a boundless ...
, 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 (see extinct comet
An extinct comet is a comet that has expelled most of its volatile ice and has little left to form a tail and coma. In a dormant comet, rather than being depleted, any remaining volatile components have been sealed beneath an inactive surface la ...
).
It is suggested that these main-belt asteroid-comets are evidence of a recent impact exposing an icy interior to solar radiation.
/ref> As a dual-status object, astrometric
Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way.
History ...
observations of 118401 LINEAR should be reported under the minor planet designation.perihelion
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values.
Apsides perta ...
on 2017 March 12.
References
External links
118401
on November 13, 2011
LINEAR home page
Seiichi Yoshida's comet list
*
*
{{DEFAULTSORT:Linear, 176P
118401
176P
0176
118401
118401
Named minor planets
19990907