163693 Atira
Discovery [1] | |
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Discovered by | LINEAR |
Discovery site | MRO |
Discovery date | 11 February 2003 |
Designations | |
MPC designation | 163693 Atira |
Named after |
Atira (goddess of the Pawnee)[2] |
2003 CP20 | |
Atira (Apohele or IEO) · NEO · Venus-crosser | |
Orbital characteristics [1] | |
Epoch 13 January 2016 (JD 2457400.5) | |
Uncertainty parameter 0 | |
Observation arc | 4467 days (12.23 yr) |
Aphelion | 0.97975 AU (146.569 Gm) |
Perihelion | 0.50232 AU (75.146 Gm) |
0.74104 AU (110.858 Gm) | |
Eccentricity | 0.32214 |
0.64 yr (233.0 d) | |
234.79° | |
1.5451°/day | |
Inclination | 25.619° |
103.92° | |
252.95° | |
Earth MOID | 0.207224 AU (31.0003 Gm) |
Jupiter MOID | 4.42023 AU (661.257 Gm) |
Physical characteristics | |
Dimensions |
±1 km 2.7[3] 1.63 km (calculated)[4] |
2.9745 h[lower-alpha 1] | |
0.20 (assumed)[4] | |
S [4] | |
16.3[1][3] | |
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163693 Atira, provisional designation 2003 CP20, is an eccentric, stony asteroid, dwelling in the interior of Earth's orbit. It is classified as a near-Earth object and measures about 2 kilometers in diameter. The body was discovered by the Lincoln Near-Earth Asteroid Research project's station at the U.S. Magdalena Ridge Observatory in Socorro, New Mexico, on 11 February 2003.[2]
It is the namesake and the first numbered body of a new subclass of near-Earth asteroids, the Atira (Apohele) asteroids, which have their orbits entirely within that of Earth and are therefore alternatively called Interior-Earth Objects (IEO).[1][5][6] As of 2015, there are only 16 known members of the Atira group of asteroids. Atiras are similar to the larger group of Aten asteroids, as both are near-Earth objects and both have a semi-major axis smaller than that of Earth (< 1.0 AU). However, and contrary to Aten asteroids, the aphelion for Atiras is always smaller than Earth's perihelion (< 0.983 AU),[7] which means that they do not approach Earth as close as Atens do in general. The body has an Earth Minimum orbit intersection distance (MOID) of 0.2065 AU (30,890,000 km).[1]
The S-type asteroid orbits the Sun at a distance of 0.5–1.0 AU once every 8 months (233 days). Its orbit is significantly tilted by 26 degrees to the plane of the ecliptic and shows a high eccentricity of 0.32. It has a rotation period of almost 3 hours[lower-alpha 1] and an albedo of 0.20, assumed by the Collaborative Asteroid Lightcurve Link (CALL).[4] With a perihelion of 0.50 AU the body also classifies as a Venus-crosser – as Venus orbits the Sun at a distance of 0.72–0.73 AU – but does not get as close to the Sun as Mercury (which orbits at 0.31–0.47 AU).
Knowing that traditionally the first known object in a new class of asteroids will become the name of the new class of asteroids, due consideration was given to the name for (163693). The other classes of near-Earth asteroids are Amors, Apollos, and Atens (as mentioned above), named after a Roman, Greek, and Egyptian god, so a preference was given to a god or goddess beginning with the letter "A". Given (163693) was discovered by the LINEAR program which operates out of the southwestern United States, preference was also given to a name of local origin. The minor planet was named after Atira, a goddess of the Native American Pawnee people. She is the wife of the creator god, Tirawa, and goddess of Earth and the evening star.[2][8]
See also
- 2007 EB26 and (434326) 2004 JG6 – members of the Atira (Apohele) group
- Committee on Small Body Nomenclature
- Provisional designation in astronomy § Minor planets
References
- 1 2 Pravec (2003) web: rotation period ±0.0006 hours with a brightness amplitude of 2.9745 mag. Summary figures at 0.36Collaborative Asteroid Lightcurve Link (CALL) for (163693) Atira
- 1 2 3 4 5 "JPL Small-Body Database Browser: 163693 Atira (2003 CP20)" (2015-05-06 last obs.). Jet Propulsion Laboratory. Retrieved 25 March 2016.
- 1 2 3 "163693 Atira (2003 CP20)". Minor Planet Center. Retrieved December 2015.
- 1 2 "(163693) Atira – PHYSICAL INFORMATION". NEODyS: Near Earth Objects – Dynamic Site. Retrieved December 2015.
- 1 2 3 4 "LCDB Data for (163693) Atira". Asteroid Lightcurve Database (LCDB). Retrieved December 2015.
- ↑ Wm. Robert Johnston. "Names of Solar System objects and features". Archived from the original on 12 April 2010. Retrieved 2010-04-03.
- ↑ Shoemaker, E. M. (December 1982). "Asteroid and comet bombardment of the earth". Annual Review of Earth and Planetary Sciences 11: 461–494. Bibcode:1983AREPS..11..461S. doi:10.1146/annurev.ea.11.050183.002333. Retrieved December 2015.
- ↑ "NEO Groups". Jet Propulsion Laboratory. Retrieved December 2015.
- ↑ "www.godfinder.org". www.godfinder.org. Archived from the original on June 9, 2014. Retrieved 2014-06-15.
External links
- Discovery Circumstances
- Orbital Information
- Photo
- Asteroid Lightcurve Database (LCDB), query form (info)
- Dictionary of Minor Planet Names, Google books
- Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
- Discovery Circumstances – Numbered Minor Planets (160001)–(165000)
- 163693 Atira at the JPL Small-Body Database
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