118401 LINEAR (

provisional designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...

, comet designation 176P/LINEAR) is an

active asteroid Active asteroids are small Solar System bodies that have asteroid-like orbits but show comet-like visual characteristics. That is, they show a coma, tail, or other visual evidence of mass-loss (like a comet), but their orbits remain within Jupite ...

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 A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or coma surrounding the nucleus, and ...

on November 26, 2005, by Henry H. Hsieh and

David C. Jewitt David Clifford Jewitt (born 1958) is a British-American astronomer who studies the Solar System, especially its minor bodies. He is based at the University of California, Los Angeles, where he is a Member of the Institute for Geophysics and Pla ...

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 Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...

), 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. It is estimated short-period comets remain active for about 10,000 years before having most of their ice sublimated away and going dormant. Eight other objects are classified as both periodic comets and numbered asteroids:

2060 Chiron 2060 Chiron is a ringed small Solar System body in the outer Solar System, orbiting the Sun between Saturn and Uranus. Discovered in 1977 by Charles Kowal, it was the first-identified member of a new class of objects now known as centaurs— ...

(95P/Chiron),

4015 Wilson–Harrington 4015 Wilson–Harrington is an active asteroid known both as comet 107P/Wilson–Harrington and as asteroid 4015 Wilson–Harrington. It passed from Earth on 20 July 2022 and then passed perihelion (closest approach to the Sun) on 24 August 2 ...

(107P/Wilson–Harrington),

7968 Elst–Pizarro Comet Elst–Pizarro is a body that displays characteristics of both asteroids and comets, and is the prototype of active asteroids. Its orbit keeps it within the asteroid belt, yet it displayed a dust tail like a comet while near perihelion in 1 ...

(133P/Elst–Pizarro),

60558 Echeclus 60558 Echeclus is a centaur, approximately in diameter , located in the outer Solar System. It was discovered by Spacewatch in 2000 and initially classified as a minor planet with provisional designation (also written 2000 EC98). Research in ...

(174P/Echeclus), (282P/2003 BM₈₀), (288P/2006 VW₁₃₉), (362P/2008 GO₉₈), and (433P/2005 QN₁₇₃).M.P.C. 133823
/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 A formal minor-planet designation is, in its final form, a number–name combination given to a minor planet (asteroid, centaur, trans-Neptunian object and dwarf planet but not comet). Such designation always features a leading number (catalog or ...

. 118401 LINEAR last came to

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