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2391 Tomita, provisional designation 1957 AA, is a Nysian asteroid from the inner regions of the asteroid belt, approximately 15 kilometers in diameter. The asteroid was discovered on 9 January 1957, by German astronomer Karl Reinmuth at Heidelberg Observatory in southern Germany. It was named after Japanese astronomer Kōichirō Tomita.

Orbit and classification

Tomita is a member of the Nysa family, which is named after its most massive member 44 Nysa. It orbits the Sun in the inner main-belt at a distance of 2.1–2.8 AU once every 3 years and 10 months (1,393 days). Its orbit has an eccentricity of 0.13 and an inclination of 3° with respect to the ecliptic.

A first precovery was taken at Lowell Observatory in 1929, extending the body's observation arc by 28 years prior to its official discovery observation at Heidelberg.

Physical characteristics

Tomita has been characterized as a stony S-type asteroid by the Collaborative Asteroid Lightcurve Link (CALL), and as a carbonaceous C-type asteroid by Pan-STARRS' photometric survey.

Diameter and albedo

According to the surveys carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the asteroid measures between 15.07 and 19.4 kilometers in diameter and its surface has a low albedo between 0.03 and 0.07, respectively.

As CALL considers the body to be of a stony composition, it assumes a much higher albedo of 0.21 and calculates a diameter of 9.2 kilometers, as the higher the asteroid's reflectivity (albedo), the shorter its diameter at a constant absolute magnitude (brightness).

Rotation period

In December 2013, two rotational lightcurves were obtained for this asteroid from photometric observations. They gave a rotation period of 7.9533±0.0005 and 8.435±0.079 hours with a brightness variation of 0.14 and 0.15 in magnitude, respectively. (U=3/n.a.).

Naming

This minor planet was named in honor of Japanese astronomer Kōichirō Tomita (1925–2006), long-time observer at the Tokyo Astronomical Observatory, and a discoverer of minor planets and comets himself. Tomita was also known as one of Japan's principal popularizer of astronomy. The official naming citation was published by the Minor Planet Center on 14 April 1987 (M.P.C. 11748).

Notes

1. ^ Pravec (2013) web: lightcurve plot with a rotation period 7.9533±0.0005 hours with a brightness amplitude of 0.14 mag. Summary figures for (2391) Tomita at Collaborative Asteroid Lightcurve Link (CALL) and Pravec, P.; Wolf, M.; Sarounova, L. (2013)
2. ^ Williams (2013) web: rotation period 8.435±0.079 hours with a brightness amplitude of 0.15 mag. Summary figures for (2391) Tomita at Collaborative Asteroid Lightcurve Link (CALL). Data by Williams, R. (2013), posted on CALL page.

References

1. ^ "JPL Small-Body Database Browser: 2391 Tomita (1957 AA)" (2016-11-23 last obs.). Jet Propulsion Laboratory. Retrieved 13 June 2017.
2. ^ Schmadel, Lutz D. (2007). "(2391) Tomita". Dictionary of Minor Planet Names – (2391) Tomita. Springer Berlin Heidelberg. p. 195. doi:10.1007/978-3-540-29925-7_2392. ISBN 978-3-540-00238-3.
3. ^ "LCDB Data for (2391) Tomita". Asteroid Lightcurve Database (LCDB). Retrieved 14 August 2016.
4. ^ Nugent, C. R.; Mainzer, A.; Masiero, J.; Bauer, J.; Cutri, R. M.; Grav, T.; et al. (December 2015). "NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos". The Astrophysical Journal. 814 (2): 13. arXiv:1509.02522. Bibcode:2015ApJ...814..117N. doi:10.1088/0004-637X/814/2/117. S2CID 9341381. Retrieved 13 June 2017.
5. ^ Nugent, C. R.; Mainzer, A.; Bauer, J.; Cutri, R. M.; Kramer, E. A.; Grav, T.; et al. (September 2016). "NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos". The Astronomical Journal. 152 (3): 12. arXiv:1606.08923. Bibcode:2016AJ....152...63N. doi:10.3847/0004-6256/152/3/63.
6. ^ 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. S2CID 46350317. Retrieved 14 August 2016.
7. ^ 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. S2CID 119293330. Retrieved 7 December 2016.
8. ^ 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. S2CID 35447010. Retrieved 14 August 2016.
9. ^ Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. S2CID 53493339. Retrieved 14 August 2016.
10. ^ "2391 Tomita (1957 AA)". Minor Planet Center. Retrieved 14 August 2016.
11. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 14 August 2016.

External links

• Asteroid Lightcurve Database (LCDB), query form (info Archived 16 December 2017 at the Wayback Machine)
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• 2391 Tomita at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 2391 Tomita at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters

• Minor planet object articles (numbered)
• Nysa asteroids
• Discoveries by Karl Wilhelm Reinmuth
• Named minor planets
• Astronomical objects discovered in 1957