|
Discovery
|
|
|---|---|
| Discovered by | LINEAR |
| Discovery date | September 7, 1999 |
|
Designations
|
|
| Named after | Lincoln Near-Earth Asteroid Research |
| Alternate name(s) | 1999 RE70 |
| Minor planet category |
Main-belt[1] (Themis) Main-belt comet[2][3] |
| Epoch July 23, 2010 (JD 2455400.5) T_jup = 3.166 |
|
| Aphelion | 3.8121 AU (570.28 Gm) |
| Perihelion | 2.5754 AU (385.27 Gm) |
| Semi-major axis | 3.1938 AU (a) (477.78 Gm) |
| Eccentricity | 0.19362 |
| Orbital period | 5.71 yr (2084.7 d) |
| Average orbital speed | 16.51 km/s |
| Mean anomaly | 300.54° |
| Inclination | 0.23766° |
| Longitude of ascending node | 346.53° |
| Argument of perihelion | 35.866° |
|
Physical characteristics
|
|
| Dimensions | 4.0±0.4 km (Spitzer)[4] |
| Mass | 4.3×1013? kg[5] |
| Mean density | 1.3? g/cm³ (assumed) |
| Equatorial surface gravity | <0.0017 m/s² |
| Escape velocity | <0.0032 km/s |
| Rotation period | ? d |
| Albedo | 0.06±0.02R[4] |
| Temperature | ~156 K |
| Spectral type | ? |
| Apparent magnitude | 18.19 to 21.91 |
| Absolute magnitude (H) | 15.1[1] |
| Discovery | |
|---|---|
| Discovered by: | LINEAR |
| Orbital characteristics A | |
| Epoch: | November 6, 2005 (JD 2453680.5) |
| Aphelion: | 3.811678 AU |
| Perihelion: | 2.5811186 AU |
| Semi-major axis: | 3.19640 AU |
| Eccentricity: | 0.1924908 |
| Orbital period: | 5.714 a |
| Inclination: | 0.23795° |
| Last perihelion: | October 18, 2005 |
| Next perihelion: | June 30, 2011 |
118401 LINEAR (provisional designation 1999 RE70) is an asteroid and main-belt comet (176P/LINEAR)[2][3] 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.[4]
The main-belt comets are unique in that they have flat (within the plane of the planets' orbits), approximately circular (small eccentricity), 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.[2] 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).[6] As a dual-status object, astrometric observations of 118401 LINEAR should be reported under the minor planet designation.[6]
118401 LINEAR will come to perihelion on 2011 July 2.[1]
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| Periodic comets (by number) | ||
|---|---|---|
| Previous 175P/Hergenrother |
176P/LINEAR | Next 177P/Barnard |
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