(9942) 1989 TM1

(9942) 1989 TM1, provisional designation 1989 TM1, is a background asteroid from the central region of the asteroid belt, approximately 4.5 kilometers (2.8 miles) in diameter. It was discovered on 8 October 1989, by Japanese astronomers Nobuhiro Kawasato and Tsutomu Hioki at the Okutama Observatory (877) in Japan.[1] The asteroid has a tentative rotation period of 3.1 hours.[3]

(9942) 1989 TM1
Discovery [1]
Discovered byT. Hioki
N. Kawasato
Discovery siteOkutama Obs.
Discovery date8 October 1989
Designations
(9942) 1989 TM1
1989 TM1
main-belt [1][2] · (middle) [3]
background
Orbital characteristics [2]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc26.64 yr (9,732 days)
Aphelion3.0287 AU
Perihelion2.1619 AU
2.5953 AU
Eccentricity0.1670
4.18 yr (1,527 days)
217.94°
0° 14m 8.52s / day
Inclination9.9393°
21.747°
38.492°
Physical characteristics
Mean diameter
4.12±0.45 km[4]
4.73 km (calculated)[3]
3.0706±0.0004 h[5]
0.20 (assumed)[3]
0.454±0.106[4]
S (assumed)[3]
13.40[4] · 13.541[5]
13.6[2] · 13.99[3]

    Orbit and classification
    Orbits of 1989 TM1 (blue) and the inner planets and Jupiter

    The assumed stony S-type is a non-family asteroid from the main belt's background population. It orbits the Sun in the central main-belt at a distance of 2.2–3.0 AU once every 4 years and 2 months (1,527 days; semi-major axis of 2.6 AU). Its orbit has an eccentricity of 0.17 and an inclination of 10° with respect to the ecliptic.[2]

    Its first observation was a precovery taken at the Palomar Observatory on 30 September 1989, extending the asteroid's observation arc by just 9 days prior to its official discovery observation.[1]

    Numbering and naming

    This minor planet was numbered by the Minor Planet Center on 2 February 1999.[6] As of 2018, it has not been named.[1]

    Physical characteristics

    Diameter and albedo

    The asteroid was predicted to cross the focal plane array of the Infrared Astronomical Satellite (IRAS). However, it was missed on each of its seven planned observation and was never detected. According to the "missed predictions file" of the supplemental IRAS minor planet survey (SIMPS), the body was expected to have a diameter of 13.5 kilometers and an absolute magnitude of 13.20.[7]

    Based on an absolute magnitude of 13.99, and an assumed standard albedo for stony asteroids of 0.20, the Collaborative Asteroid Lightcurve Link calculated a much smaller diameter of 4.7 kilometers,[3] which agrees with a diameter of 4.1 kilometers, found by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission.[4]

    Rotation period

    In October 2010, a rotational lightcurve for this asteroid was obtained from photometric observations at the Palomar Transient Factory in California. It rendered a tentative rotation period of 3.0706±0.0004 hours with a brightness variation of 0.08 in magnitude (U=1).[5]

    References
    1. "9942 (1989 TM1)". Minor Planet Center. Retrieved 13 September 2018.
    2. "JPL Small-Body Database Browser: 9942 (1989 TM1)" (2018-05-19 last obs.). Jet Propulsion Laboratory. Retrieved 13 September 2018.
    3. "LCDB Data for (9942)". Asteroid Lightcurve Database (LCDB). Retrieved 4 July 2016.
    4. Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.; et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters. 759 (1): 5. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8.
    5. Waszczak, Adam; Chang, Chan-Kao; Ofek, Eran O.; Laher, Russ; Masci, Frank; Levitan, David; et al. (September 2015). "Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry". The Astronomical Journal. 150 (3): 35. arXiv:1504.04041. Bibcode:2015AJ....150...75W. doi:10.1088/0004-6256/150/3/75.
    6. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 13 September 2018.
    7. Tedesco E.F.; Noah P.V.; Noah M.; Price S.D. "The supplemental IRAS minor planet survey (SIMPS) – Missed-Predictions". Retrieved 1 January 2016.

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