Atira asteroid


Atira asteroids or Apohele asteroids, also known as interior-Earth objects, are asteroids whose orbits are entirely confined within Earth's orbit; that is, their orbit has an aphelion smaller than Earth's perihelion, which is 0.983 astronomical units. Atira asteroids are by far the smallest group of near-Earth objects, compared to the Aten, Apollo and Amor asteroids.

Asteroids

The first suspected Apohele was, and the first confirmed was 163693 Atira in 2003., there are 22 known Apoheles, of which 18 have robust orbit determinations, of which six have been computed with sufficient precision to receive a permanent number . An additional 78 objects have aphelia smaller than Earth's aphelion. The Near Earth Object Surveillance Satellite is intended to find more.
On 4 January 2020, the Zwicky Transient Facility discovered, whose aphelion distance is only 0.656 AU, which is entirely within the orbit of Venus, which never gets less than 0.718 AU from the Sun. However, no asteroids have yet been discovered inside the orbit of Mercury., the asteroid with the smallest known aphelion is, with an aphelion of 0.656 AU, followed by with Q = 0.774 AU and with Q = 0.794 AU.
Apoheles 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 resembles the one induced by the Kozai-Lidov mechanism, which contributes to enhanced long-term stability, there is no libration of the value of the argument of perihelion.
Vatira asteroids are a subclass of Atiras that orbit entirely interior to the orbit of Venus. They were theorized to exist at least since 2012, and in early 2020, the first Vatira asteroid was discovered:.

Name

There is no standard name for the class. The name Apohele was proposed by the discoverers of, and is the Hawaiian word for orbit, from apo 'circle' and hele 'to go'; it was chosen partially because of its similarity to the words aphelion and helios. Other authors adopted the designation Inner Earth Objects. 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.
'Vatira' is a conflation of 'Atira' with the 'v' of 'Venus'.

Members