Atira asteroid

The group of Atira (Apohele) asteroids compared to the orbits of the terrestrial planets of the Solar System.
  Mars (M)
  Venus (V)
  Mercury (H)		   Sun
  Atira asteroids
  Earth (E)

Atira asteroids or Apohele asteroids, also known as Interior-Earth Objects (IEOs), are asteroids, whose orbits are entirely confined within Earth's orbit,[1] that is, their orbit has an aphelion (farthest point from the Sun) smaller than Earth's perihelion (nearest point to the Sun), which is 0.983 astronomical units (AU). Atira asteroids are by far the smallest group of near-Earth objects, compared to the Aten, Apollo and Amor asteroids.[2]

The first suspected Apohele was 1998 DK36, and the first confirmed was 163693 Atira in 2003. There are 18 suspected Apoheles,[2] of which 15 have well-known orbits, of which six have been determined with sufficient precision to receive a permanent number (see § List below).[3] An additional 58 objects (not listed) have aphelia smaller than Earth's aphelion (1.017 AU).[4] The Near Earth Object Surveillance Satellite is intended to find more.

In great part because of the search methods used to look for asteroids, there are currently no known asteroids with orbits contained within Venus or Mercury's (e.g. vulcanoids).

There is no standard name for the class. The name Apohele was proposed by the discoverers of 1998 DK36,[5] and is the Hawaiian word for orbit; it was chosen partially because of its similarity to the words aphelion (apoapsis) and helios.[lower-alpha 1] Other authors adopted the designation Inner Earth Objects (IEOs).[6] Still others, following the general practice to name a new class of asteroids for the first recognized member of that class,[7][8] use the designation Atira asteroids.[1]

Apoheles do not cross Earth's orbit and are not immediate impact threats, but their orbits may be perturbed outward by a close approach to either Mercury or Venus and become Earth-crossing asteroids in the future. The orbits of many of these objects are strongly affected by the Kozai-Lidov mechanism, which contributes to enhanced long-term stability.[9]

List

List of known and suspected Apoheles as of May 2018 (Q < 0.983 AU)[3]
Designation Perihelion
(AU)		 Semi-major axis
(AU)		 Aphelion
(AU)		 Eccentricity Inclination
(°)		 Period
(days)		 Observation arc
(days)		 (H) Diameter(A)
(m)		 Discoverer Ref
Mercury (for comparison)0.3070.38710.4670.20567.0188NA-0.64,879,400NA
Venus (for comparison)0.7180.72330.7280.00683.39225NA-4.512,103,600NA
1998 DK360.4040.69230.9800.41602.02210125.035David J. TholenMPC
163693 Atira0.5020.74110.9800.322125.62233519216.34,800+1,000(B)LINEARList
(164294) 2004 XZ1300.3370.61760.8980.45462.95177356420.4300David J. TholenList
(434326) 2004 JG60.2980.63520.9730.531218.94185403518.4740LONEOSList
(413563) 2005 TG450.4280.68140.9350.372223.33205429517.61,100Catalina Sky SurveyList
2013 JX28 (=2006 KZ39)0.2620.60080.9400.564210.76170289320.1340Mount Lemmon Survey
Pan-STARRS		MPC
2006 WE40.6410.78470.9280.182924.77254408118.9590Mount Lemmon SurveyMPC
(418265) 2008 EA320.4280.61590.8040.305028.26177312616.51,800Catalina Sky SurveyList
(481817) 2008 UL900.4310.69500.9590.379824.31212344118.7650Mount Lemmon SurveyList
2010 XB110.2880.6180.9480.533929.88177181119.9450Mount Lemmon SurveyMPC
2012 VE460.4550.71290.9710.36156.67220113520.2320Pan-STARRSMPC
2013 TQ50.6530.77370.8940.155616.4024980519.8390Mount Lemmon SurveyMPC
2014 FO470.5480.75210.9560.271119.20238140720.3310Mount Lemmon SurveyMPC
2015 DR2150.3520.66640.9810.47164.0919940420.3310Pan-STARRSMPC
2015 ME1310.6450.80490.9710.198928.88264219.5450Pan-STARRSMPC
2017 XA10.6460.80960.9730.201617.182664121.2200Pan-STARRSMPC
2017 YH0.3280.63450.9410.482419.8318539118.5710SpacewatchMPC
2018 JB30.4850.68320.8820.290540.402061217.51,120Catalina Sky SurveyMPC
(A) All diameter estimates are based on an assumed albedo of 0.14 (except 163693 Atira, for which the size has been directly measured)
(B) Binary asteroid

Pseudo-Atiras

Two further asteroids technically pass further from the Sun than Earth does at its closest, but due to the eccentricity of Earth's orbit, still remain entirely within it. The known pseudo-Atira asteroids are listed below:

List of pseudo-Atiras as of May 2018 (Q < 1.017 AU)
Designation Perihelion
(AU)		 Semi-major axis
(AU)		 Aphelion
(AU)		 Eccentricity Inclination
(°)		 Period
(days)		 Observation arc
(days)		 (H) Diameter(A)
(m)		 Discoverer Ref
2009 SZ990.4810.81480.9890.214421.33269213319.5450Mount Lemmon SurveyMPC
2017 TF20.4470.71540.9840.375113.862211320.4300Mount Lemmon SurveyMPC

See also

References

  1. ↑ Cambridge Conference Correspondence, (2): WHAT'S IN A NAME: APOHELE = APOAPSIS & HELIOS – from Dave Tholen, Cambridge Conference Network (CCNet) DIGEST, 9 July 1998
    Benny,
    Duncan Steel has already brought up the subject of a class name for objects with orbits interior to the Earth's. To be sure, we've already given that subject some thought. I also wanted a word that begins with the letter "A", but there was some desire to work Hawaiian culture into it. I consulted with a friend of mine that has a master's degree in the Hawaiian language, and she recommended "Apohele", the Hawaiian word for "orbit". I found that an interesting suggestion, because of the similarity to fragments of "apoapsis" and "helios", and these objects would have their apoapsis closer to the Sun than the Earth's orbit. By the way, the pronunciation would be like "ah-poe-hey-lay". Rob Whiteley has suggested "Ali`i", which refers to the Hawaiian elite, which provides a rich bank of names for discoveries in this class, such as Kuhio, Kalakaua, Kamehameha, Liliuokalani, and so on. Unfortunately, I think the okina (the reverse apostrophe) would be badly treated by most people.
    I wasn't planning to bring it up at this stage, but because Duncan has already done so, here's what we've got on the table so far. I'd appreciate some feedback on the suggestions.
    --Dave
  1. 1 2 "Near-Earth Object Groups". JPL – NASA. Retrieved 11 November 2016.
  2. 1 2 "Near-Earth Asteroid Discovery Statistics". 14 December 2017. Retrieved 30 December 2017.
  3. 1 2 "JPL Small-Body Database Search Engine: Q < 0.983 (AU)". JPL Solar System Dynamics. Retrieved 30 December 2017.
  4. ↑ "Asteroids with aphelia between 0.983 and 1.017 AU". Retrieved 30 December 2017.
  5. ↑ Tholen, D. J.; Whiteley, R. J. (September 1998). "Results From NEO Searches At Small Solar Elongation". American Astronomical Society. 30: 1041. Bibcode:1998DPS....30.1604T. Retrieved 11 November 2016.
  6. ↑ Michel, Patrick; Zappalà, Vincenzo; Cellino, Alberto; Tanga, Paolo (February 2000). "NOTE: Estimated Abundance of Atens and Asteroids Evolving on Orbits between Earth and Sun". Icarus. 143 (2): 421–424. Bibcode:2000Icar..143..421M. doi:10.1006/icar.1999.6282. Retrieved 11 November 2016.
  7. ↑ Wm. Robert Johnston (24 August 2006). "Names of Solar System objects and features". www.johnstonsarchive.net. Retrieved 11 November 2016.
  8. ↑ 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 11 November 2016.
  9. ↑ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (11 June 2018). "Kozai--Lidov Resonant Behavior Among Atira-class Asteroids". Research Notes of the AAS. 2 (2): 46. arXiv:1806.00442. Bibcode:2018RNAAS...2b..46D. doi:10.3847/2515-5172/aac9ce.
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