1999 Hirayama

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1999 Hirayama
Discovery
Discovered by Luboš Kohoutek[1]
Discovery date February 27, 1973[1]
Designations
Named after
Kiyotsugu Hirayama[1]
1935 GF; 1940 EH;
1951 EY1; 1951 FA;
1965 UF; 1969 NB;
1973 DR; 1975 NE
Minor planet category Main belt
Orbital characteristics
Epoch June 14, 2006 (JD 2453900.5)
Aphelion 516.937 Gm (3.456 AU)
Perihelion 416.446 Gm (2.784 AU)
466.692 Gm (3.120 AU)
Eccentricity 0.108
2012.590 d(5.51 a)
16.81 km/s
26.858°
Inclination 12.489°
148.349°
355.105°
Physical characteristics
Dimensions 34.0 km
Mass 4.1×1016 kg
Mean density
2.0 g/cm³
0.0095 m/s²
0.0180 km/s
15.63 ± 0.01 h[2]
Albedo 0.10?
Temperature ~158 K
Spectral type
?
10.6[2]

1999 Hirayama is an asteroid discovered by Luboš Kohoutek at Bergedorf in 1973. It is named after Kiyotsugu Hirayama,[1] the Japanese astronomer best known for his discovery that many asteroid orbits were more similar to one another than chance would allow, leading to the concept of asteroid families, now called Hirayama families.

The light curve of 1999 Hirayama shows a periodicity of 15.63 ± 0.01 hours, during which time the brightness of the object varies by 0.45 ± 0.04 in magnitude.[2] The spectrum of this object matches a C-type Tholen classification, but with a "broad absorption band that can be associated to a process of aqueous alteration".[3] That is, the surface appears to show some form of water modification.

References[edit]

  1. ^ a b c d Schmadel, Lutz (2003), Dictionary of Minor Planet Names, Physics and astronomy online library 1 (5th ed.), Springer, p. 162, ISBN 3540002383. 
  2. ^ a b c Menke, John et al. (October 2008), "Asteroid Lightcurve Analysis at Menke Observatory", The Minor Planet Bulletin (Minor Planets Section of the Association of Lunar and Planetary Observers) 35 (4): 155–160, Bibcode:2008MPBu...35..155M 
  3. ^ Lazzaro, D. et al. (November 2004), "S3OS2: the visible spectroscopic survey of 820 asteroids", Icarus 172 (1): 179–220, Bibcode:2004Icar..172..179L, doi:10.1016/j.icarus.2004.06.006.