118401 LINEAR, provisional designation , is an asteroid and main-belt comet (176P/LINEAR)(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 objects ...

(LINEAR) 1-metre telescopes in Socorro, New Mexico on September 7, 1999. (118401) LINEAR was discovered to be

cometary A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are ...

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 A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, th ...

's 2.2-m (88-in) telescope on December 24–27, 2005, and Gemini on December 29, 2005. Observations using the Spitzer Space Telescope 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-like

orbit In celestial mechanics, an orbit 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 object or position in space such as ...

s, and not the elongated, often tilted orbits characteristic of all other comets. Because (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 The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, its

ice Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaqu ...

heats up and sublimates (changes directly from ice to

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

), venting gas and

dust Dust is made of 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 process), volcanic eruptions, and pollution. Dust in ho ...

into

space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually cons ...

, 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 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—bodies o ...

(95P/Chiron), 4015 Wilson–Harrington (107P/Wilson–Harrington), 7968 Elst–Pizarro (133P/Elst–Pizarro), 60558 Echeclus (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 observations of 118401 LINEAR should be reported under the minor planet designation. 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. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

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