Atira asteroid

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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 13 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.[a] 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.

List[edit]

List of known and suspected Apoheles as of December 2017 (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)
Ref
1998 DK36 0.404 0.6923 0.98 0.4160 2.02 210 1 25.0 35 MPC
163693 Atira 0.502 0.7411 0.98 0.3221 25.62 233 5192 16.3 4,800+1,000(B) List
(164294) 2004 XZ130 0.337 0.6176 0.90 0.4546 2.95 177 3564 20.4 300 List
(434326) 2004 JG6 0.298 0.6352 0.97 0.5312 18.94 185 4035 18.4 740 List
(413563) 2005 TG45 0.428 0.6814 0.94 0.3722 23.33 205 4295 17.6 1,100 List
2013 JX28 (=2006 KZ39) 0.262 0.6008 0.94 0.5642 10.76 170 2893 20.1 340 MPC
2006 WE4 0.641 0.7847 0.93 0.1830 24.77 254 3263 18.9 590 MPC
2007 EB26 0.116 0.5476 0.98 0.7887 8.49 148 5 19.6 430 MPC
(418265) 2008 EA32 0.428 0.6159 0.80 0.3050 28.26 177 3126 16.5 1,800 List
(481817) 2008 UL90 0.431 0.6948 0.96 0.3802 24.31 212 1917 18.6 680 List
2010 XB11 0.288 0.618 0.95 0.5339 29.88 177 1811 19.9 450 MPC
2012 VE46 0.455 0.7129 0.97 0.3615 6.67 220 1135 20.2 320 MPC
2013 TQ5 0.653 0.7737 0.89 0.1556 16.40 249 805 19.8 390 MPC
2014 FO47 0.548 0.7522 0.96 0.2711 19.20 238 686 20.3 310 MPC
2015 DR215 0.352 0.6664 0.98 0.4716 4.09 199 404 20.3 310 MPC
2015 ME131 0.645 0.8049 0.96 0.1989 28.88 264 2 19.5 450 MPC
2017 XA1 0.646 0.8095 0.97 0.2017 17.17 266 5 21.4 190 MPC
2017 YH 0.329 0.6348 0.94 0.4816 19.77 185 15 18.4 740 MPC
(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

See also[edit]

References[edit]

  1. ^ Cambridge Conference Correspondence, (2): WHAT'S IN A NAME: APOHELE = APOAPSIS & HELIOSfrom 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. ^ a b "Near-Earth Object Groups". JPL – NASA. Retrieved 11 November 2016. 
  2. ^ a b "Near-Earth Asteroid Discovery Statistics". 14 December 2017. Retrieved 30 December 2017. 
  3. ^ a b "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. 

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