Atira asteroid

Atira asteroids or Apohele asteroids, also known as interior-Earth objects (IEOs), are Near-Earth objects 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 least numerous group of near-Earth objects, compared to the more populous Aten, Apollo and Amor asteroids.

History

Naming

Atira asteroids are the most recently discovered group of near-Earth objects. The first Atira asteroid detected was 1998 DK36 in 1998, and at that time, its discoverers proposed the name "Apohele" to refer to this group of asteroids, after the Hawaiian word for orbit, from apo [ˈɐpo] 'circle' and hele [ˈhɛlɛ] 'to go'. This was suggested partly because of its similarity to the words aphelion (apoapsis) and helios. Other authors adopted the designation "Inner Earth Objects" (IEOs). But 1998 DK36 was considered a lost minor planet. Therefore, it has a claim to title "first Apohele detected" but not "first Apohele confirmed", which goes to 163693 Atira. Following the general practice to name a new class of asteroids for the first confirmed member of that class, which in this case was 163693 Atira, the designation of "Atira asteroids" was largely adopted by the scientific community, including by NASA, by 2010.

Discovery and observation

Their location inside the Earth's orbit makes Atiras very difficult to observe, as from Earth's perspective they are close to the Sun and therefore 'drowned out' by the Sun's overpowering light.