2391 Tomita

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2391 Tomita
Discovery [1]
Discovered by K. Reinmuth
Discovery site Heidelberg Obs.
Discovery date 9 January 1957
MPC designation 2391 Tomita
Named after
Kōichirō Tomita
1957 AA · 1929 VX
1938 BF · 1942 DF
1957 BA · 1977 KM
1978 PA4 · 1980 DC6
main-belt · Nysa[3]
Orbital characteristics[1]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc 86.63 yr (31,641 days)
Aphelion 2.7678 AU
Perihelion 2.1136 AU
2.4407 AU
Eccentricity 0.1340
3.81 yr (1,393 days)
0° 15m 30.6s / day
Inclination 3.0111°
Physical characteristics
Dimensions 9.17 km (calculated)[3]
16.62±0.23 km[4]
19.412±0.175 km[5]
7.9533±0.0005 h[a]
8.435±0.079 h[b]
0.21 (assumed)[3]
S[3] · C[6]

2391 Tomita, provisional designation 1957 AA, is a Nysian asteroid from the inner regions of the asteroid belt, approximately 10–20 kilometers in diameter. It was discovered on 9 January 1957, by German astronomer Karl Reinmuth at Heidelberg Observatory in southern Germany.[7]

The asteroid is a member of the Nysa family, which is named after its most massive member 44 Nysa. While the Collaborative Asteroid Lightcurve Link (CALL) classifies this body as a stony S-type asteroid, it is considered to be a carbonaceous C-type asteroid by Pan-STARRS large-scale survey.[3][6] It orbits the Sun 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.[1] The first precovery was taken at Lowell Observatory in 1929, extending the asteroid's observation arc by 28 years prior to its discovery.[7]

According to the surveys carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the asteroid measures 16.6 and 19.4 kilometers in diameter and its surface has a low albedo of 0.03 and 0.07, respectively.[4][5] 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).[3]

In December 2013, two rotational light-curves 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.).[a][b]

The 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.[2] Naming citation was published before November 1977 (M.P.C. 2391).[8]


  1. ^ a b Pravec (2013) web: rotation period hours with a brightness amplitude of mag. Summary figures at Collaborative Asteroid Lightcurve Link (CALL) for (2391) Tomita and Pravec, P.; Wolf, M.; Sarounova, L. (2013)
  2. ^ a b Williams (2013) web: rotation period hours with a brightness amplitude of mag. Summary figures at Collaborative Asteroid Lightcurve Link (CALL) for (2391) Tomita. Data by Williams, R. (2013), posted on CALL page.
  1. ^ a b c d "JPL Small-Body Database Browser: 2391 Tomita (1957 AA)" (2016-06-13 last obs.). Jet Propulsion Laboratory. Retrieved 14 August 2016. 
  2. ^ a b Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (2391) Tomita. Springer Berlin Heidelberg. p. 195. ISBN 978-3-540-00238-3. Retrieved 14 August 2016. 
  3. ^ a b c d e f g "LCDB Data for (2391) Tomita". Asteroid Lightcurve Database (LCDB). Retrieved 14 August 2016. 
  4. ^ a b c d 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:1209.5794free to read. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8. Retrieved 14 August 2016. 
  5. ^ a b c d 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:1109.6407free to read. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 14 August 2016. 
  6. ^ a b c 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:1506.00762free to read. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 14 August 2016. 
  7. ^ a b "2391 Tomita (1957 AA)". Minor Planet Center. Retrieved 14 August 2016. 
  8. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 14 August 2016. 

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