118401 LINEAR

118401 LINEAR
176P/LINEAR
Discovery
Discovered by LINEAR
Discovery date September 7, 1999
Designations
Named after
 Lincoln Near-Earth Asteroid Research
1999 RE70
Main-belt[1] (Themis)
Main-belt comet[2][3]
Orbital characteristics[1]
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)
3.1938 AU (a)
(477.78 Gm)
Eccentricity 0.19362
5.71 yr
(2084.7 d)
16.51 km/s
300.54°
Inclination 0.23766°
346.53°
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)
<0.0017 m/s²
<0.0032 km/s
? d
Albedo 0.06±0.02R[4]
Temperature ~156 K
Spectral type
 ?
18.19 to 21.91
15.1[1]
    176P/LINEAR
    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 June 30, 2011[6]
    October 18, 2005
    Next perihelion 2017 March 12[7]

    118401 LINEAR (provisional designation 1999 RE70) is an asteroid and main-belt comet (176P/LINEAR)[2][3] that 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. Observations using the Spitzer Space Telescope have resulted in an estimate of 4.0±0.4 km for the diameter of (118401) LINEAR.[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. 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, 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 (see extinct comet).

    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).[8] As a dual-status object, astrometric observations of 118401 LINEAR should be reported under the minor planet designation.[8]

    118401 LINEAR will come to perihelion on 2017 March 12.[7]

    References

    1. ↑ 1.0 1.1 1.2 "JPL Small-Body Database Browser: 118401 LINEAR (1999 RE70)" (2010-11-02 last obs). Retrieved 2010-12-15.
    2. ↑ 2.0 2.1 2.2 Henry H. Hsieh (May 2010). "Main Belt Comets". Hawaii. Retrieved 2010-12-15. (older 2010 site)
    3. ↑ 3.0 3.1 David Jewitt. "Main Belt Comets". UCLA, Department of Earth and Space Sciences. Retrieved 2010-12-15.
    4. ↑ 4.0 4.1 4.2 Hsieh, Henry H.; Jewitt, David C.;Fernández, Yanga R. (2009). "Albedos of Main-Belt Comets 133P/ELST-PIZARRO and 176P/LINEAR". The Astrophysical Journal Letters 694 (2): L111–L114. arXiv:0902.3682. Bibcode:2009ApJ...694L.111H. doi:10.1088/0004-637X/694/2/L111.
    5. ↑ Using a spherical radius of 2 km; volume of a sphere * an assumed density of 1.3 g/cm³ yields a mass (m=d*v) of 4.3E+13 kg
    6. ↑ Syuichi Nakano (2006-10-29). "176P/LINEAR = (118401) 1999 RE70 (NK 1373)". OAA Computing and Minor Planet Sections. Retrieved 2012-02-25.
    7. ↑ 7.0 7.1 Patrick Rocher (2012-01-26). "Note number : 0701 P/LINEAR : 176P". Institut de mécanique céleste et de calcul des éphémérides. Retrieved 2012-02-25.
    8. ↑ 8.0 8.1 "Dual-Status Objects". Minor Planet Center. 2008-03-06. Retrieved 2010-12-17.

    External links

    Periodic comets (by number)
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