Atira asteroids or Apohele asteroids, also known as Interior-Earth Objects (IEOs), are asteroids, whose orbits are entirely confined within Earth's orbit, 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.
The first suspected Apohele was 1998 DK36, and the first confirmed was 163693 Atira in 2003. There are 16 suspected Apoheles, of which eight have well-known orbits, of which five have been determined with sufficient precision to receive a permanent number (see § List below). An additional 28 objects (not listed) have aphelia smaller than Earth's aphelion (1.017 AU). The Near Earth Object Surveillance Satellite is intended to find more.
There is no standard name for the class. The name Apohele was proposed by the discoverers of 1998 DK36, 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). Still others, following the general practice to name a new class of asteroids for the first recognized member of that class, use the designation Atira asteroids.
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.
|(164294) 2004 XZ130||0.337||0.6176||0.90||0.4546||2.95||177||3564||20.4||250||List|
|(434326) 2004 JG6||0.298||0.6352||0.97||0.5312||18.94||185||4035||18.4||550||List|
|(413563) 2005 TG45||0.428||0.6815||0.94||0.3723||23.33||205||3276||17.6||1,000||List|
|2013 JX28 (=2006 KZ39)||0.262||0.6008||0.94||0.5642||10.76||170||2893||20.1||330||MPC|
|(418265) 2008 EA32||0.428||0.6159||0.80||0.3050||28.26||177||3126||16.5||1,500||List|
- (A) Diameter estimates are partially unsourced
- Cambridge Conference Correspondence, (2): WHAT'S IN A NAME: APOHELE = APOAPSIS & HELIOS – from Dave Tholen, Cambridge Conference Network (CCNet) DIGEST, 9 July 1998
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.
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- "JPL Small-Body Database Search Engine: Q < 0.983 (AU)". JPL Solar System Dynamics. Retrieved 11 November 2016.
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- List Of Aten Minor Planets, Minor Planet Center