Astronomy:24 Themis

From HandWiki
24 Themis
Deconvolved image of Themis by VLT-SPHERE
Discovery
Discovered byAnnibale de Gasparis
Discovery date5 April 1853
Designations
(24) Themis
Pronunciation/ˈθiːmɪs/[1]
Named afterThemis
1947 BA; 1955 OH
Minor planet categoryMain belt (Themis)
AdjectivesThemistian[2] /θɪˈmɪstiən/[3]
Orbital characteristics[4]
Epoch 17.0 October 2024 (JD 2460600.5)
|{{{apsis}}}|helion}}524.4 Gm
(3.505 AU)
|{{{apsis}}}|helion}}415.9 Gm
(2.780 AU)
470.2 Gm
(3.143 AU)
Eccentricity0.1153
Orbital period2035 d (5.57 yr)
Mean anomaly346.1°
Inclination0.7368°
Longitude of ascending node36.39°
109.0°
Earth MOID1.79422 AU
Jupiter MOID1.50402 AU
TJupiter3.199
Physical characteristics
DimensionsTemplate:Nwr
Mean diameter208±3 km[5]
198±20 km[6]
Flattening0.24[lower-alpha 1]
Mass(6.2±2.9)×1018 kg[5]
(1.13±0.43)×1019 kg[6]
2.39×1019 kg[7][lower-alpha 2]
Mean density1.31±0.62 g/cm3[5]
2.78±1.35 g/cm3[6]
Equatorial surface gravity
0.15+0.08
−0.07 m/s2[6]
Equatorial escape velocity
87+15
−20 m/s[6]
Rotation period0.34892 d (8 h 22 min)[4]
8.374187±0.000001 h[5]
Axial tilt18°[5]
Pole ecliptic latitude73°±3°[5]
Pole ecliptic longitude146°±3°[5]
Geometric albedo0.060 (calculated)[5]
0.067[4]
C/B[4] (B-V=0.68)
Absolute magnitude (H)7.24[4]
7.08[5]


24 Themis is one of the largest asteroids in the asteroid belt. At roughly 200 kilometres (120 mi) in diameter, it is also the largest member of the Themistian family. It was discovered by Annibale de Gasparis on 5 April 1853. It is named after Themis, the personification of natural law and divine order in Greek mythology.

Discovery and observations

24 Themis was discovered on 5 April 1853 by Annibale de Gasparis of Naples, though it was given its name by fellow Italian astronomer Angelo Secchi. The asteroid was named after Themis, the Greek goddess of law.[8] Gravitational perturbations in the orbit of Themis were used to calculate the mass of Jupiter as early as 1875.[9]

On 24 December 1975, 24 Themis had a close encounter with 2296 Kugultinov with a minimum distance of 0.016 AU (2.4×10^6 km). By analyzing the perturbation of Kugultinov's orbit due to the gravitational pull of Themis, the mass of Themis was determined to be approximately 2.89×10−11 solar masses (9.62×10−6 Earth masses).[10]

Orbit and rotation

Themis is in an elliptical orbit around the Sun with an eccentricity of 0.1306 and an inclination of 0.76°.[11] It has an orbital period of 5.54 years. The distance between Themis and the Sun ranges from 2.71 AU at perihelion and 3.55 AU at aphelion,[12] with a mean distance of 3.1302 AU.[11] Themis is part of the Themis family of asteroids, which is located in the outer part of the main belt. The family consists of a core of large objects surrounded by a cloud of smaller objects; 24 Themis is a member of the core.[12]

Surface materials

Ice

On 7 October 2009, the presence of water ice was confirmed on the surface of this asteroid using NASA’s Infrared Telescope Facility.[13]Cite error: Closing </ref> missing for <ref> tag in the form of tholins, high-molecular weight organics found in the outer solar system, distinguished by a brown or reddish color in optical spectra. Compounds found in the spectra of Themis include ice tholin (the residual of an irradiated mixture of water ice and ethane), asphaltite, carbonaceous meteorite material, and polycyclic aromatic hydrocarbons.[14][15]

See also

Notes

  1. ↑ Flattening derived from the maximum aspect ratio (c/a): f=1−ca, where (c/a) = 0.76±0.08.[5]
  2. ↑ 0.12×10−11 M☉ = 2.39×1019 kg

References

  1. ↑ Noah Webster (1884) A Practical Dictionary of the English Language
  2. ↑ Astronomy now, Volume 22 (2008)
  3. ↑ Themistian (3rd ed.), Oxford University Press, September 2005, http://oed.com/search?searchType=dictionary&q=Themistian  (Subscription or UK public library membership required.)
  4. ↑ 4.0 4.1 4.2 4.3 4.4 "JPL Small-Body Database Browser: 24 Themis". 12 December 2024. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Themis. 
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56
  6. ↑ 6.0 6.1 6.2 6.3 6.4 Baer, James; Steven R. Chesley (25 June 1999). "Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris". Celest. Mech. Dyn. Astron. (Springer Science+Business Media B.V. 2007) 100 (2008): 27–42. doi:10.1007/s10569-007-9103-8. Bibcode: 2008CeMDA.100...27B. 
  7. ↑ Michalak, G. (2001). "Determination of asteroid masses". Astronomy & Astrophysics 374 (2): 703–711. doi:10.1051/0004-6361:20010731. Bibcode: 2001A&A...374..703M. 
  8. ↑ Schmadel, Lutz D. (2003). Dictionary of minor planet names (5th ed.). Springer. p. 17. ISBN 978-3-540-00238-3. https://books.google.com/books?id=KWrB1jPCa8AC&q=dictionary+of+astronomy+themis&pg=PA17. 
  9. ↑ "Our Astronomical Column". Nature 13 (316): 48. 18 November 1875. doi:10.1038/013047d0. Bibcode: 1875Natur..13...47.. https://www.nature.com/nature/journal/v13/n316/pdf/013047d0.pdf?foxtrotcallback=true. 
  10. ↑ García, A. López; Medvedev, Yu. D.; Fernández, J. A. Moraño (1997). "Using Close Encounters of Minor Planets for the Improvement of their Masses". Poznań, Poland: Kluwer Academic Publishers. pp. 199–204. ISBN 978-0-7923-4574-9. https://books.google.com/books?id=sJe_2VBDYNEC&q=Using+close+encounters+of+minor+planets+for+the+improvement+of+their+masses.&pg=PA199. 
  11. ↑ 11.0 11.1 The Astronomical Almanac. United States Naval Observatory and United Kingdom Hydrographic Office. 2011. p. G2. ISBN 978-0-7077-4103-1. 
  12. ↑ 12.0 12.1 "Dictionary of Astronomy". Oxford Dictionary of Astronomy. Oxford University Press. 27 May 2010. pp. 528. 
  13. ↑ Cowen, Ron (8 October 2009). "Ice confirmed on an asteroid". Science News. http://www.sciencenews.org/view/generic/id/48174/title/Ice_confirmed_on_an_asteroid. Retrieved 9 October 2009. 
  14. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Rivkin2010
  15. ↑ Emery, Joshua P.. "Advances in Solar System Science: Research Enabled by 2.4 – 25 μm Spectroscopy with SOFIA". https://www.sofia.usra.edu/sites/default/files/Poster_5.10_Emery.pdf. 



Retrieved from "https://handwiki.org/wiki/index.php?title=Astronomy:24_Themis&oldid=3947582"