Amor asteroid
Group of near-Earth asteroids
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Definition
The orbital characteristics that define an asteroid as being in the Amor group are:
- The orbital period is greater than one year; i.e., the orbital semi-major axis (a) is greater than 1.0 AU (a > 1.0 AU);
- The orbit does not cross that of Earth; i.e., the orbital perihelion (q) is greater than Earth's orbital aphelion (q > 1.017 AU);
- The object is a near-Earth object (NEO); i.e., q < 1.3 AU.
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Populations
As of January 2025 there are 15,175 known Amor asteroids. Of those objects, 1414 are numbered, 83 are named, and 42 are designated as a potentially hazardous asteroid.
Outer Earth-grazer asteroids
An outer Earth-grazer asteroid is an asteroid that is normally beyond Earth's orbit, but which can get closer to the Sun than Earth's aphelion (1.0167 AU), and not closer than Earth's perihelion (0.9833 AU); i.e., the asteroid's perihelion is between Earth's perihelion and aphelion. Outer Earth-grazer asteroids are split between Amor and Apollo asteroids. Using the definition of Amor asteroids above, "Earth grazers" that never get closer to the Sun than Earth does (at any point along its orbit) are Amors, whereas those that do are Apollos.
Potentially hazardous asteroids
To be considered a potentially hazardous asteroid (PHA), an object's orbit must, at some point, come within 0.05 AU of Earth's orbit, and the object itself must be sufficiently large/massive to cause significant regional damage if it impacted Earth. Most PHAs are either Aten asteroids or Apollo asteroids (and thus have orbits that cross the orbit of Earth), and as of November 2023 70 Amors are classified as a PHA, the named objects 2061 Anza, 3122 Florence, 3908 Nyx, and 3671 Dionysus.
Lists
Prominent Amor asteroids
Named Amor asteroids
This is a non-static list of named Amor asteroids.