17 Thetis is a stonyasteroid from the inner regions of theasteroid belt, approximately 90 kilometers in diameter. It was discovered on 17 April 1852, by German astronomerRobert Luther atBilk Observatory in Düsseldorf, Germany who deferred toFriedrich Wilhelm August Argelander the naming his first asteroid discovery afterThetis from Greek mythology.[3][4] Its historical symbol was a dolphin and a star; it was encoded inUnicode 17.0 as U+1CECA ().[12][13]
The asteroid orbits the Sun at a distance of 2.1–2.8 AU once every 3 years and 11 months (1,419 days). Its orbit has aneccentricity of 0.13 and aninclination of 6° with respect to theecliptic.[1]
The spectrum of this object indicates that it is anS-type asteroid with both low and high calcium forms ofpyroxene on the surface, along with less than 20%olivine. The high-calcium form of pyroxene forms 40% or more of the total pyroxene present, indicating a history ofigneous rock deposits. This suggests that the asteroid underwent differentiation by melting, creating a surface ofbasalt rock.[14]
The mass of Thetis has been calculated fromperturbations by4 Vesta and11 Parthenope. In 2007, Baer and Chesley calculated Thetis to have a mass of 1.23×1018 kg[a] with a density of 3.21 g/cm3.[9]One Thetidianstellaroccultation was observed fromOregon in 1999. However, the event was not timed.
^ab"17 Thetis".Minor Planet Center. Retrieved24 March 2017.
^Herbert (1828)Nimrod: a discourse on certain passages of history and fable, vol. 2
^abMasiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos".The Astrophysical Journal.791 (2): 11.arXiv:1406.6645.Bibcode:2014ApJ...791..121M.doi:10.1088/0004-637X/791/2/121.
^abMichalowski, T.; Velichko, F. P.; Di Martino, M.; Krugly, Yu. N.; Kalashnikov, V. G.; Shevchenko, V. G.; et al. (December 1995). "Models of four asteroids: 17 Thetis, 52 Europa, 532 Herculina, and 704 Interamnia".Icarus.118 (2):292–301.Bibcode:1995Icar..118..292M.doi:10.1006/icar.1995.1192.
^Sunshine, Jessica M.; Bus, Schelte J.; McCoy, Timothy J.; Burbine, Thomas H.; Corrigan, Catherine M.; Binzel, Richard P. (August 2004). "High-calcium pyroxene as an indicator of igneous differentiation in asteroids and meteorites".Meteoritics and Planetary Science.39 (8):1343–1357.Bibcode:2004M&PS...39.1343S.doi:10.1111/j.1945-5100.2004.tb00950.x.
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