Atira asteroidAtira 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.
1862 ApolloSpectral typeQ(Tholen, SMASS)B–V = 0.819U–B = 0.481Absolute magnitude (H)16.091862 Apollo is a stony asteroid, approximately 1.5 kilometers in diameter, classified as a near-Earth object (NEO). It was discovered by German astronomer Karl Reinmuth at Heidelberg Observatory on 24 April 1932, but was lost and not recovered until 1973.Aten asteroidThe Aten asteroids are a dynamical group of asteroids whose orbits bring them into proximity with Earth. By definition, Atens are Earth-crossing asteroids(a < 1.0 AU and Q > 0.983 AU). The group is named after 2062 Aten, the first of its kind, discovered on 7 January 1976 by American astronomer Eleanor Helin at Palomar Observatory.
Near-Earth objectSmall Solar System body with an orbit that can bring it close to Earth37,000+ known NEOs, divided into several orbital subgroupsApollos: 21,132 (56.5%)Amors: 13,137 (35.1%)Atens: 2,952 (7.90%)Comets: 123 (0.33%)Atiras: 34 (0.09%)A near-Earth object (NEO) is by definition any small Solar System body orbiting the Sun whose closest approach to the Sun (perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU).
List of Earth-crossing asteroidsAn Earth-crosser is a near-Earth asteroid whose orbit crosses that of Earth as observed from the ecliptic pole of Earth's orbit. The known numbered Earth-crossers are listed here. Those Earth-crossers whose semi-major axes are smaller than Earth's are Aten asteroids; the remaining ones are Apollo asteroids. (See also the Amor asteroids.)An asteroid with an Earth-crossing orbit is not necessarily in danger of colliding with Earth.
Amor asteroidThe Amor asteroids are a group of near-Earth asteroids named after the archetype object 1221 Amor . The orbital perihelion of these objects is close to, but greater than, the orbital aphelion of Earth (i.e., the objects do not cross Earth's orbit), with most Amors crossing the orbit of Mars. The Amor asteroid 433 Eros was the first asteroid to be orbited and landed upon by a robotic space probe (NEAR Shoemaker).
Astronomical unitThe astronomical unit (symbol: au or AU) is a unit of length defined as 149597870700 m. Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its modern redefinition in 2012. The astronomical unit is used primarily for measuring distances within the Solar System or around other stars. It is also a fundamental component in the definition of another unit of astronomical length, the parsec.
Minor-planet designationThere are three internationally standardized designations for minor planets, which are assigned by the Minor Planet Center (MPC). In order of assignment, these are: 1. an initial provisional designation, for all announced discoveries, that reflects the date of discovery;2. a permanent designation: a catalog number assigned sequentially once the object has a securely determined orbit;and, for a little under 2% of objects, 3.
Opposition (astronomy)In positional astronomy, two astronomical objects are said to be in opposition when they are on opposite sides of the celestial sphere, as observed from a given body (usually Earth). A planet (or asteroid or comet) is said to be "in opposition" or "at opposition" when it is in opposition to the Sun.
ApsisAn apsis (from Ancient Greek (hapsís)'arch, vault' (third declension); pl.apsides ) is one of the two extreme points in the orbit of a planetary body about its primary body, either the farthest point (apoapsis) or the nearest point (periapsis). The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two apsides. Apsides pertaining to orbits around different bodies have distinct names to differentiate themselves from other apsides.Karl Wilhelm ReinmuthKarl Wilhelm Reinmuth (4 April 1892 in Heidelberg – 6 May 1979 in Heidelberg) was a German astronomer and a prolific discoverer of 395 minor planets.*As an Amazon Associate I earn from qualifying purchases.