17 Thetis

17 Thetis
Star field showing asteroid Thetis in the center
Discovery
Discovered byR. Luther
Discovery siteDüsseldorf-Bilk Obs.
Discovery date17 April 1852
Designations
Pronunciation/ˈθiːtɪs/
Named after
Thetis (Greek mythology)
1954 SO1 · A913 CA
A916 YF
main-belt · (inner)
AdjectivesThetidian /θɛˈtɪdiən/
Symbol𜻊 (historical)
Orbital characteristics
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 0
Observation arc164.55 yr (60,102 days)
Aphelion2.7987 AU
Perihelion2.1436 AU
2.4712 AU
Eccentricity0.1325
3.88 yr (1,419 days)
18.87 km/s
100.44°
0° 15m 13.32s / day
Inclination5.5902°
125.56°
14 September 2027
136.10°
Physical characteristics
82.76±8.79 km
(composite estimate)
Individual estimates:
  • 84.899±2.027 km
  • 90±3.7 km (IRAS)
  • 93.335±2.627 km
Mass(5.7±1.5)×1017 kg
Mean density
1.80 g/cm3
12.27048±0.00001
0.193±0.028
B–V = 0.829
U–B = 0.438
S (Tholen)
Sl (SMASS) · S
7.91 · 7.76 · 7.85
Lightcurve-base 3D-model of 17 Thetis.
Lightcurve-base 3D-model of 17 Thetis.

17 Thetis is a stony asteroid from the inner regions of the asteroid belt, approximately 90 kilometers in diameter. It was discovered on 17 April 1852, by German astronomer Robert Luther at Bilk Observatory in Düsseldorf, Germany who deferred to Friedrich Wilhelm August Argelander the naming his first asteroid discovery after Thetis from Greek mythology. Its historical symbol was a dolphin and a star; it was encoded in Unicode 17.0 as U+1CECA 𜻊 ().

Description

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 an eccentricity of 0.13 and an inclination of 6° with respect to the ecliptic.

The spectrum of this object indicates that it is an S-type asteroid with both low and high calcium forms of pyroxene 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 of igneous rock deposits. This suggests that the asteroid underwent differentiation by melting, creating a surface of basalt rock.

The mass of Thetis has been calculated from perturbations by 4 Vesta and 11 Parthenope. In 2007, Baer and Chesley calculated Thetis to have a mass of 1.23×1018 kg with a density of 3.21 g/cm3. One Thetidian stellar occultation was observed from Oregon in 1999. However, the event was not timed.

This minor planet was named after Thetis, the mother of Achilles in Greek mythology.

Notes

  1. ↑ Calculated from its standard gravitational parameter GM = 0.038±0.010 km3/s2.
  2. ↑ Assuming a diameter of 84.9 km.
  3. ↑ Mass of Thetis = (6.17±0.64)×10−13 M☉

References

  1. 1 2 3 4 5 6 7 8 "JPL Small-Body Database Browser: 17 Thetis" (2016-11-11 last obs.). Jet Propulsion Laboratory. Retrieved 24 March 2017.
  2. ↑ Noah Webster (1884) A Practical Dictionary of the English Language
  3. 1 2 3 Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (17) Thetis. Springer Berlin Heidelberg. p. 17. doi:10.1007/978-3-540-29925-7_18. ISBN 978-3-540-00238-3.
  4. 1 2 "17 Thetis". Minor Planet Center. Retrieved 24 March 2017.
  5. ↑ Herbert (1828) Nimrod: a discourse on certain passages of history and fable, vol. 2
  6. ↑ Carry, B. (December 2012), "Density of asteroids", Planetary and Space Science, vol. 73, pp. 98–118, arXiv:1203.4336, Bibcode:2012P&SS...73...98C, doi:10.1016/j.pss.2012.03.009. See Table 1.
  7. 1 2 Masiero, 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.
  8. 1 2 Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 30 October 2019.
  9. 1 2 Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90.
  10. 1 2 Fuentes-Muñoz, Oscar; Farnocchia, Davide; Giorgini, Jon D.; Park, Ryan S. (1 December 2025). "Asteroid Mass Estimation by Mutual Perturbations During Close Encounters After Gaia Focused Product Release". The Astronomical Journal. 170 (6): 353. Bibcode:2025AJ....170..353F. doi:10.3847/1538-3881/ae0cc9. ISSN 0004-6256. S2CID 283347135.
  11. 1 2 "MinorPlanet.info: One Asteroid Information". Asteroid Lightcurve Database (LCDB). Search using Number = "17"
  12. 1 2 Michalowski, 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.
  13. ↑ Bala, Gavin Jared; Miller, Kirk (18 September 2023). "Unicode request for historical asteroid symbols" (PDF). unicode.org. Unicode. Retrieved 26 September 2023.
  14. ↑ "Miscellaneous Symbols Supplement" (PDF). unicode.org. The Unicode Consortium. 2025. Retrieved 9 September 2025.
  15. ↑ 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.
  16. ↑ Baer, James; Chesley, Steven R. (January 2008). "Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris". Celestial Mechanics and Dynamical Astronomy. 100 (1): 27–42. Bibcode:2008CeMDA.100...27B. doi:10.1007/s10569-007-9103-8.