The Amor asteroids are a group of

near-Earth asteroid A near-Earth object (NEO) is 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). This definition applies to the object's orbit aro ...

s named after the archetype object

1221 Amor 1221 Amor is an asteroid and near-Earth object on an eccentric orbit, approximately in diameter. It is the namesake of the Amor asteroids, the second-largest subgroup of near-Earth objects. It was discovered by Eugène Delporte at the Uccle ...

. The orbital

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

of these objects is close to, but greater than, the orbital

aphelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

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 433 Eros is a stony asteroid of the Amor group, and the first discovered, and second-largest near-Earth object. It has an elongated shape and a volume-equivalent diameter of approximately . Visited by the NEAR Shoemaker space probe in 1998, ...

was the first asteroid to be

orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

ed and landed upon by a robotic

space probe Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board. Uncrewed spacecraft may have varying levels of autonomy from human input, such as remote control, or remote guidance. They may also be autonomous, in which th ...

(

NEAR Shoemaker ''Near Earth Asteroid Rendezvous – Shoemaker'' (''NEAR Shoemaker''), renamed after its 1996 launch in honor of planetary scientist Eugene Merle Shoemaker, Eugene Shoemaker, was a Robotic spacecraft, robotic space probe designed by the Johns ...

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 A near-Earth object (NEO) is 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). This definition applies to the object's orbit a ...

(NEO); i.e., ''q'' < 1.3 AU.

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

(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 Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...

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 3908 Nyx is an Amor asteroid, Amor and Mars-crosser asteroid. It was discovered by Hans-Emil Schuster on August 6, 1980, and is named after Nyx (mythology), Nyx, the Greek mythology, Greek goddess of the night, after which Pluto's natural satel ...

Definition

Populations

Outer Earth-grazer asteroids

Potentially hazardous asteroids

Lists

Prominent Amor asteroids

Named Amor asteroids

See also

References

External links