TheAmor asteroids are a group ofnear-Earth asteroids named after the archetype object1221 Amor/ˈeɪmɔːr/. The orbitalperihelion of these objects is close to, but greater than, the orbitalaphelion of Earth (i.e., the objects do not cross Earth's orbit),[1] with most Amors crossing the orbit of Mars. The Amor asteroid433 Eros was the first asteroid to beorbited and landed upon by a roboticspace probe (NEAR Shoemaker).
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 apotentially hazardous asteroid.[3][4]
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'saphelion (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 andApollo 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.
To be considered apotentially 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 eitherAten asteroids orApollo 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 objects2061 Anza,3122 Florence,3908 Nyx, and3671 Dionysus.[5]
