Жер орбитасының ішіндегі астероидтар тобы

Group of near Earth asteroids

Atira asteroids /ə/'/t//ɪr//ə/ or Apohele asteroids, also known as interior Earth objects (IEOs), are Near Earth objects whose orbits are entirely confined within Earth's orbit; This was suggested partly because of its similarity to the words aphelion (apoapsis) and helios. Other authors adopted the designation "Inner Earth Objects" (IEOs). An additional 127 objects have aphelia smaller than Earth's aphelion (Q = 1.017 AU). A number of known Atiras could be fragments or former moons of larger Atiras as they exhibit an unusually high level of orbital correlation.

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. The dynamics of many Atira asteroids resemble the one induced by the Kozai Lidov mechanism, which contributes to enhanced long term orbital stability, since there is no libration of the perihelion.

A 2017 study published in the journal Advances in Space Research proposed a low cost space probe be sent to study Atira asteroids, citing the difficulty in observing the group from Earth as a reason to undertake the mission. The study proposed that the mission would be powered by spacecraft electric propulsion and would follow a path designed to flyby as many Atira asteroids as possible. The probe would also attempt to discover new NEO's that may pose a threat to Earth. Observations suggest that ꞌAylóꞌchaxnim asteroids frequently have their orbits altered into Atira asteroids and vice versa. First formally theorised to exist by William F. Bottke and Gianluca Masi in 2002 and 2003, the first and to date only such asteroid found is 594913 ꞌAylóꞌchaxnim, It has an aphelion of only 0.656 AU, making it the asteroid with the smallest known aphelion.