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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 /əˈtɪrə/ 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]

Asteroids[]

The first suspected was 1998 DK36, and the first confirmed, was 163693 Atira in 2003. As of February 2022, there are 28 known Atiras,[2] of which 24 have robust orbit determinations, of which seven have been computed with sufficient precision to receive a permanent number.[3] An additional 127 objects (not listed below) have aphelia smaller than Earth's aphelion (Q = 1.017 AU).[4]

The Near Earth Object Surveillance Satellite is currently searching to find more.

Atiras do not cross Earth's orbit and are not immediate impact event 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. Although the dynamics of many of these objects somehow resemble the one induced by the Kozai-Lidov mechanism (coupled oscillations in eccentricity and inclination), which contributes to enhanced long-term stability, there is no libration of the value of the argument of perihelion.[5][6]

Vatira asteroids[]

Vatira asteroids are a subclass of Atiras that orbit entirely interior to the orbit of Venus (whose perihelion q = 0.718 AU). The name "Vatira" is provisional, combining "Venus" with "Atira". They were theorized to exist at least since 2012,[7] and in early 2020, the first Vatira asteroid was discovered: 594913 ꞌAylóꞌchaxnim.[8][9][10] It was discovered on 4 January 2020 by the Zwicky Transient Facility. Its aphelion distance is only 0.656 AU.[11][12] Being the prototype, its name will be used to refer to this population.[7] As of January 2020, it is the asteroid with the smallest known aphelion,[3][5] followed by 2019 AQ3 with Q = 0.774 AU and 2019 LF6 with Q = 0.794 AU.[13]

Vulcanoid asteroids[]

Main article: Vulcanoid

No asteroids have yet been discovered to orbit entirely inside the orbit of Mercury (q = 0.307 AU). Such hypothetical asteroids would likely be termed vulcanoids, although the term often refers to asteroids which more specifically have remained in the intra-Mercurian region over the age of the solar system.[7]

Name[]

There is no standard name for the class. Following the general practice to name a new class of asteroids for the first recognized member of that class,[14][15] some astronomers,[16][17][18][19] and this article, use the designation Atira asteroids.[1]

The name Apohele was proposed by the discoverers of 1998 DK36.[20] It is the Hawaiian word for orbit, from apo [ˈɐpo] 'circle' and hele [ˈhɛlɛ] 'to go';[21] it was chosen partly because of its similarity to the words aphelion (apoapsis) and helios.[a]

Other authors adopted the designation Inner Earth Objects (IEOs).[22]

Members[]

The following table lists the known and suspected Atiras as of February 2022. The sole known Vatira asteroid 594913 ꞌAylóꞌchaxnim has been highlighted in pink. The planets Mercury and Venus have been included for comparison (grey rows).

List of known and suspected Atiras as of February 2021 (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)		 0.307 0.3871 0.467 0.2056 7.01 88 NA -0.6 4,879,400 NA
Venus
(for comparison)		 0.718 0.7233 0.728 0.0068 3.39 225 NA -4.5 12,103,600 NA
1998 DK36 0.404 0.6923 0.980 0.4160 2.02 210 1 25.0 35 David J. Tholen MPC · JPL
163693 Atira 0.502 0.7410 0.980 0.3222 25.62 233 6601 16.3 4800±500(B) LINEAR List
MPC · JPL
(164294) 2004 XZ130 0.337 0.6176 0.898 0.4546 2.95 177 3564 20.4 300 David J. Tholen List
MPC · JPL
(434326) 2004 JG6 0.298 0.6353 0.973 0.5311 18.94 185 6227 18.5 710 LONEOS List
MPC · JPL
(413563) 2005 TG45 0.428 0.6814 0.935 0.3722 23.33 205 5814 17.6 1,100 Catalina Sky Survey List
MPC · JPL
2013 JX28
(aka 2006 KZ39)		 0.262 0.6008 0.940 0.5641 10.76 170 5110 20.1 340 Mount Lemmon Survey
Pan-STARRS		 MPC · JPL
(613676) 2006 WE4 0.641 0.7848 0.928 0.1829 24.77 254 4995 18.9 590 Mount Lemmon Survey List
MPC · JPL
(418265) 2008 EA32 0.428 0.6159 0.804 0.3050 28.26 177 4794 16.5 1,800 Catalina Sky Survey List
MPC · JPL
(481817) 2008 UL90 0.431 0.6951 0.959 0.3798 24.31 212 4496 18.6 680 Mount Lemmon Survey List
MPC · JPL
2010 XB11 0.288 0.6180 0.948 0.5339 29.89 177 1811 19.9 370 Mount Lemmon Survey MPC · JPL
2012 VE46 0.455 0.7131 0.971 0.3613 6.67 220 2225 20.2 320 Pan-STARRS MPC · JPL
2013 TQ5 0.653 0.7737 0.894 0.1557 16.40 249 2269 19.8 390 Mount Lemmon Survey MPC · JPL
2014 FO47 0.548 0.7522 0.956 0.2712 19.20 238 2779 20.3 310 Mount Lemmon Survey MPC · JPL
2015 DR215 0.352 0.6665 0.981 0.4716 4.08 199 2156 20.4 300 Pan-STARRS MPC · JPL
2017 XA1 0.646 0.8095 0.973 0.2017 17.18 266 1084 21.3 200 Pan-STARRS MPC · JPL
2017 YH
(aka 2016 XJ24)		 0.328 0.6343 0.940 0.4825 19.85 185 1127 18.4 740 Spacewatch
ATLAS		 MPC · JPL
2018 JB3 0.485 0.6832 0.882 0.2904 40.39 206 2037 17.7 1,020 Catalina Sky Survey MPC · JPL
2019 AQ3 0.404 0.5887 0.774 0.3143 47.22 165 2175 17.5 1,120 Zwicky Transient Facility MPC · JPL
2019 LF6 0.317 0.5554 0.794 0.4293 29.51 151 796 17.3 1,230 Zwicky Transient Facility MPC · JPL
594913 ꞌAylóꞌchaxnim 0.457 0.5554 0.654 0.1770 15.87 151 609 16.2 1500+1100
−600		 Zwicky Transient Facility MPC · JPL
2020 HA10 0.692 0.8196 0.947 0.1552 49.65 271 3248 18.9 590 Mount Lemmon Survey MPC · JPL
2020 OV1 0.476 0.6376 0.800 0.2541 32.58 186 1169 18.9 590 Zwicky Transient Facility MPC · JPL
2021 BS1 0.396 0.5984 0.800 0.3377 31.73 169 46 18.5 710 Zwicky Transient Facility MPC · JPL
2021 LJ4 0.416 0.6748 0.933 0.3834 9.83 202 5 20.1 340 Scott S. Sheppard MPC · JPL
2021 PB2 0.610 0.7174 0.825 0.1501 24.83 222 3392 18.8 620 Zwicky Transient Facility MPC · JPL
2021 PH27 0.133 0.4617 0.790 0.7117 31.93 115 1515 17.7 1,020 Scott S. Sheppard MPC · JPL
2021 VR3 0.313 0.5339 0.755 0.4138 18.06 143 1012 18.0 890 Zwicky Transient Facility MPC · JPL
2022 BJ8 0.590 0.7852 0.981 0.2487 15.83 254 7 19.7 400 Kitt Peak-Bok MPC · JPL
(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[]

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 "Aliʻi", 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. Archived from the original on 2 February 2002. Retrieved 11 November 2016.
  2. ^ a b "Near-Earth Asteroid Discovery Statistics". 14 May 2019. Retrieved 25 May 2019.
  3. ^ a b c "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 25 May 2019.
  5. ^ a b 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. S2CID 119239031.
  6. ^ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (1 August 2019). "Understanding the evolution of Atira-class asteroid 2019 AQ3, a major step towards the future discovery of the Vatira population". Monthly Notices of the Royal Astronomical Society. 487 (2): 2742–2752. arXiv:1905.08695. Bibcode:2019MNRAS.487.2742D. doi:10.1093/mnras/stz1437. S2CID 160009327.
  7. ^ a b c Greenstreet, Sarah; Ngo, Henry; Gladman, Brett (January 2012). "The orbital distribution of Near-Earth Objects inside Earth's orbit" (PDF). Icarus. 217 (1): 355–366. Bibcode:2012Icar..217..355G. doi:10.1016/j.icarus.2011.11.010. hdl:2429/37251. We have provisionally named objects with 0.307 < Q < 0.718 AU Vatiras, because they are Atiras which are decoupled from Venus. Provisional because it will be abandoned once the first discovered member of this class will be named.
  8. ^ Masi, Gianluca (9 January 2020). "2020 AV2, the first intervenusian asteroid ever discovered: an image – 08 Jan. 2020". Virtual Telescope Project. Retrieved 9 January 2020.
  9. ^ Plait, Phil (10 January 2020). "Meet 2020 AV2, the first asteroid found that stays inside Venus's orbit!". Bad Astronomy. Syfy Wire. Retrieved 10 January 2020.
  10. ^ Popescu, M.; de León, J.; de la Fuente Marcos, C.; Vaduvescu, O.; de la Fuente Marcos, R.; Licandro, J.; Pinter, V.; Zamora, O.; Fariña, C.; Curelaru, L. (11 August 2020). "Physical characterization of 2020 AV2, the first known asteroid orbiting inside Venus orbit". Monthly Notices of the Royal Astronomical Society. 496 (3): 3572–3581. arXiv:2006.08304. Bibcode:2020MNRAS.496.3572P. doi:10.1093/mnras/staa1728. S2CID 219687045. Retrieved 8 July 2020.
  11. ^ Greenstreet, Sarah (6 February 2020). "Orbital Dynamics of 2020 AV2: the First Vatira Asteroid". Monthly Notices of the Royal Astronomical Society: Letters. 493 (1): L129–L131. arXiv:2001.09083. Bibcode:2020MNRAS.493L.129G. doi:10.1093/mnrasl/slaa025. S2CID 210911743.
  12. ^ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (11 February 2020). "On the orbital evolution of 2020 AV2, the first asteroid ever observed to go around the Sun inside the orbit of Venus". Monthly Notices of the Royal Astronomical Society: Letters. 494 (1): L6. arXiv:2002.03033. Bibcode:2020MNRAS.494L...6D. doi:10.1093/mnrasl/slaa027. S2CID 211068996.
  13. ^ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (25 July 2019). "Hot and Eccentric: The Discovery of 2019 LF6 as a New Step in the Quest for the Vatira Population". Research Notes of the American Astronomical Society. 3 (7): 106. Bibcode:2019RNAAS...3g.106D. doi:10.3847/2515-5172/ab346c. S2CID 201405666.
  14. ^ Wm. Robert Johnston (24 August 2006). "Names of Solar System objects and features". www.johnstonsarchive.net. Retrieved 11 November 2016.
  15. ^ 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.
  16. ^ Plait, Phil (24 August 2021). "Meet 2021 PH27, a newly discovered asteroid with the shortest known year!". SYFY WIRE.
  17. ^ Di Carlo, Marilena; Romero Martin, Juan Manuel; Ortiz Gomez, Natalia; Vasile, Massimiliano (April 2017). "Optimised low-thrust mission to the Atira asteroids". Advances in Space Research. 59 (7): 1724–1739. doi:10.1016/j.asr.2017.01.009.
  18. ^ Ribeiro, A. O.; Roig, F.; De Prá, M. N.; Carvano, J. M.; DeSouza, S. R. (1 June 2016). "Dynamical study of the Atira group of asteroids". Monthly Notices of the Royal Astronomical Society. 458 (4): 4471–4476. doi:10.1093/mnras/stw642.
  19. ^ de la Fuente Marcos, C.; de la Fuente Marcos, R. (1 August 2019). "Understanding the evolution of Atira-class asteroid 2019 AQ3, a major step towards the future discovery of the Vatira population". Monthly Notices of the Royal Astronomical Society. 487 (2): 2742–2752. arXiv:1905.08695. doi:10.1093/mnras/stz1437.
  20. ^ 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.
  21. ^ (Ulukau Hawaiian Electronic Library)
  22. ^ 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.

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