118401 LINEAR

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**118401 LINEAR**
Discovery ^A

Discoverer	LINEAR
Discovery date	September 7, 1999
Alternate designations ^B	1999 RE₇₀
Category	Main belt (Themis), Comet
Orbital elements ^C
Epoch June 14, 2006 (JD 2453900.5)
Eccentricity (e)	0.192
Semi-major axis (a)	478.120 G m (3.196 AU)
Perihelion (q)	386.104 Gm (2.581 AU)
Aphelion (Q)	570.136 Gm (3.811 AU)
Orbital period (P)	2086.967 d (5.71 a)
Mean orbital speed	16.51 km/s
Inclination (i)	0.238°
Longitude of the ascending node (Ω)	346.572°
Argument of perihelion (ω)	36.141°
Mean anomaly (M)	41.182°
Physical characteristics ^D
Dimensions	<6.0 km
Mass	<2.3×10¹⁴ kg
Density	2.0? g/cm³
Surface gravity	<0.0017 m/s²
Escape velocity	<0.0032 km/s
Rotation period	? d
Spectral class	?
Absolute magnitude	15.1
Albedo (geometric)	0.10?
Mean surface temperature	~156 K

**176P/LINEAR**
Comet (List of comets)
No image.
Discovery
Discoverer	LINEAR
Discovery date	October 18, 2005
Alternate designations	1999 RE₇₀
Orbital elements ^A
Epoch November 6, 2005 (JD 2453680.5)
Eccentricity (e)	0.1924908
Semi-major axis (a)	3.19640 AU
Perihelion (q)	2.5811186 AU
Aphelion (Q)	3.811678 AU
Orbital period (P)	5.714 a
Inclination (i)	0.23795°
Last perihelion date	October 18, 2005
Next est. perihelion date	June 30, 2011

118401 LINEAR (provisional designation 1999 RE₇₀) is an asteroid and main-belt comet (176P/LINEAR, also known as LINEAR 52) 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. Based on an absolute magnitude (H) of 15.04, (118401) LINEAR is assumed to be smaller than 6 km in diameter.

The main-belt comets are unique in that they have flat, circular, asteroid-like orbits, 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.

[edit] References

Comets
Previous periodic comet	176P/LINEAR	Next periodic comet

Minor planets
Previous minor planet	118401 LINEAR	Next minor planet

v • d • e</span> Small Solar System bodies
Vulcanoids \| Near-Earth asteroids \| Main belt \| Jupiter Trojans \| Centaurs \| Damocloids \| Comets \| Trans-Neptunians (Kuiper belt · Scattered disc · Oort cloud)
For other objects and regions, see: asteroid groups and families, binary asteroids, asteroid moons and the Solar system For a complete listing, see: List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names.