1999 Hirayama

Modelled shape of Hirayama from its lightcurve

Discovery[1]
Discovered by| L. Kohoutek
Discovery site| Bergedorf Obs.
Discovery date| 27 February 1973
Designations

MPC designation

| (1999) Hirayama
Named after| Kiyotsugu Hirayama
(Japanese astronomer)[2]

Alternative designations

| 1973 DR * 1935 GF
1940 EH * 1951 EY1
1951 FA * 1965 UF
1969 NB * 1975 NE
Minor planet category| main-belt * (outer) [3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc| 77.24 yr (28,212 days)
|{{{apsis}}}|helion}}| 3.4757 AU
|{{{apsis}}}|helion}}| 2.7575 AU

Semi-major axis

| 3.1166 AU
Eccentricity| 0.1152
Orbital period| 5.50 yr (2,010 days)
Mean anomaly| 39.370°
Mean motion| 0° 10m 44.76s / day
Inclination| 12.529°
Longitude of ascending node| 148.03°

|{{{apsis}}}|helion}}

| 357.05°
Physical characteristics
Mean diameter| 33.77 km (derived)[3]
33.95±2.1 km[4]
35.68±0.55 km[5]
38.28±0.40 km[6]
Rotation period| 13.5921±0.0003 h[lower-alpha 1]
15.63±0.01 h[7]
22.37±0.03 h[8]
Geometric albedo| 0.053±0.005[6]
0.0617 (derived)[3]
0.082±0.003[5]
0.0882±0.012[4]

Spectral type

| C[3][9]
Absolute magnitude (H)| 10.6[4][5] * 10.78±0.31[9] * 10.90[6] * 11.0[1][3]

1999 Hirayama (prov. designation: 1973 DR) is a dark background asteroid from the outer region of the asteroid belt, approximately 34 kilometers (21 miles) in diameter. It was discovered on 27 February 1973, by Czech astronomer Luboš Kohoutek at the Hamburger Bergedorf Observatory in Germany, and later named after Japanese astronomer Kiyotsugu Hirayama.[2][10]

## Contents

* 1 Orbit and classification
* 2 Naming
* 3 Physical characteristics
* 3.1 Rotation period
* 3.2 Diameter and albedo
* 4 Notes
* 5 References
* 6 External links

## Orbit and classification

Hirayama orbits the Sun in the outer main-belt at a distance of 2.8–3.5 AU once every 5 years and 6 months (2,010 days). Its orbit has an eccentricity of 0.12 and an inclination of 13° with respect to the ecliptic.[1] The spectrum of Hirayama matches a C-type classification on the Tholen taxonomic scheme, but with a "broad absorption band that can be associated to a process of aqueous alteration".[11] That is, the surface appears to show some form of water modification.

## Naming

This minor planet is named in honour of Japanese astronomer Kiyotsugu Hirayama (1874–1943), 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 lunar crater Hirayama is also named in his honour.[2] The official naming citation was published by the Minor Planet Center on 15 October 1977 (M.P.C. 4237).[12]

## Physical characteristics

### Rotation period

A rotational lightcurve of Hirayama was obtained at the Menke Observatory in February 2002. It showed a periodicity of 15.63±0.01 hours, during which time the brightness of Hirayama varies by 0.45±0.04 in magnitude ({{{1}}}).[7] At the same time, photometric observations by astronomers Roberto Crippa and Federico Manzini gave a rotation period of 22.37 hours and a brightness variation of 0.47 magnitude ({{{1}}}).[8] These results supersede an observation from January 2005, by Hiromi and Hiroko Hamanowa at their Hamanowa Astronomical Observatory, Japan, that gave a shorter period of 13.59 hours with an amplitude of 0.57 magnitude.({{{1}}}).[lower-alpha 1]

### Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the asteroid measures between 34.0 and 38.3 kilometers in diameter and its surface has an albedo between 0.053 and 0.088.[4][5][6] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.062 and a diameter of 33.8 kilometers with an absolute magnitude of 11.0.[3]

## Notes

1. ↑ 1.0 1.1 Hamanowa (2011) web: rotation period 13.5921±0.0003 hours with a brightness amplitude of 0.57 mag. Summary figures at Collaborative Asteroid Lightcurve Link (CALL) for (1999) Hirayama

## References

1. ↑ 1.0 1.1 1.2 1.3 "JPL Small-Body Database Browser: 1999 Hirayama (1973 DR)". Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2001999. Retrieved 1 July 2017.
2. ↑ 2.0 2.1 2.2 Schmadel, Lutz D. (2007). "(1999) Hirayama". Dictionary of Minor Planet Names – (1999) Hirayama. Springer Berlin Heidelberg. p. 162. doi:10.1007/978-3-540-29925-7_2000. ISBN 978-3-540-00238-3.
3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Template:Cite LCDB
4. ↑ 4.0 4.1 4.2 4.3 Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System – IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode: 2004PDSS...12.....T. https://sbnarchive.psi.edu/pds3/iras/IRAS_A_FPA_3_RDR_IMPS_V6_0/data/diamalb.tab. Retrieved 17 October 2019.
5. ↑ 5.0 5.1 5.2 5.3 Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan 63 (5): 1117–1138. doi:10.1093/pasj/63.5.1117. Bibcode: 2011PASJ...63.1117U. (online, AcuA catalog p. 153)
6. ↑ 6.0 6.1 6.2 6.3 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. doi:10.1088/2041-8205/759/1/L8. Bibcode: 2012ApJ...759L...8M. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2012ApJ...759L...8M. Retrieved 8 December 2016.
7. ↑ 7.0 7.1 Menke, John; Cooney, Walt; Gross, John; Terrell, Dirk; Higgins, David (October 2008). "Asteroid Lightcurve Analysis at Menke Observatory". Minor Planet Bulletin 35 (4): 155–160. ISSN 1052-8091. Bibcode: 2008MPBu...35..155M. http://www.minorplanet.info/MPB/issues/MPB_35-4.pdf. Retrieved 17 March 2020.
8. ↑ 8.0 8.1 Behrend, Raoul. "Asteroids and comets rotation curves – (1999) Hirayama". Geneva Observatory. http://obswww.unige.ch/~behrend/page4cou.html#001999. Retrieved 8 December 2016.
9. ↑ 9.0 9.1 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. doi:10.1016/j.icarus.2015.08.007. Bibcode: 2015Icar..261...34V. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2015Icar..261...34V. Retrieved 8 December 2016.
10. ↑ "1999 Hirayama (1973 DR)". Minor Planet Center. https://www.minorplanetcenter.net/db_search/show_object?object_id=1999. Retrieved 8 December 2016.
11. ↑ Lazzaro, D.; Angeli, C. A.; Carvano, J. M.; Mothé-Diniz, T.; Duffard, R.; Florczak, M. (November 2004). "S3OS2: the visible spectroscopic survey of 820 asteroids". Icarus 172 (1): 179–220. doi:10.1016/j.icarus.2004.06.006. Bibcode: 2004Icar..172..179L. http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2004Icar..172..179L. Retrieved 8 December 2016.
12. ↑ Schmadel, Lutz D. (2009). "Appendix – Publication Dates of the MPCs". Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008). Springer Berlin Heidelberg. p. 221. doi:10.1007/978-3-642-01965-4. ISBN 978-3-642-01964-7. https://archive.org/details/dictionaryminorp2008schm.

## External links

* Lightcurve Database Query (LCDB), at www.minorplanet.info
* Dictionary of Minor Planet Names, Google books
* Asteroids and comets rotation curves, CdR – Geneva Observatory, Raoul Behrend
* Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
* 1999 Hirayama at AstDyS-2, Asteroids—Dynamic Site
* Ephemeris * Observation prediction * Orbital info * Proper elements * Observational info
* 1999 Hirayama at the JPL Small-Body Database
* Close approach * Discovery * Ephemeris * Orbit diagram * Orbital elements * Physical parameters

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