
The Apollo 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
1862 Apollo
1862 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 lost and not recovered unti ...
, discovered by German astronomer
Karl Reinmuth
Karl Wilhelm Reinmuth (4 April 1892 in Heidelberg – 6 May 1979 in Heidelberg) was a German astronomer and a prolific discoverer of 395 minor planets.
Scientific career
From 1912 to 1957, Reinmuth was working as an astronomer at the He ...
in the 1930s. They are
Earth-crossing asteroid
An 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 E ...
s that have an orbital
semi-major axis
In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...
greater than that of the Earth (a > 1
AU) but
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 ...
distances less than the Earth's
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 ...
distance (q < 1.017 AU).
, the number of known Apollo asteroids is 21,083, making the class the largest group of
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 ...
s (''cf''. the
Aten
Aten, also Aton, Atonu, or Itn (, reconstructed ) was the focus of Atenism, the religious system formally established in ancient Egypt by the late Eighteenth Dynasty pharaoh Akhenaten. Exact dating for the Eighteenth Dynasty is contested, thou ...
,
Amor and
Atira asteroids), of which 1,742 are
numbered (asteroids are not numbered until they have been observed at two or more
oppositions), 81 are named, and 2,130 are identified as
potentially hazardous asteroids
A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the Impact event, event ...
.
The closer their semi-major axis is to Earth's, the less
eccentricity
Eccentricity or eccentric may refer to:
* Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal"
Mathematics, science and technology Mathematics
* Off-Centre (geometry), center, in geometry
* Eccentricity (g ...
is needed for the
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 ...
s to cross. The
Chelyabinsk meteor, that exploded over the city of
Chelyabinsk
Chelyabinsk; , is the administrative center and largest types of inhabited localities in Russia, city of Chelyabinsk Oblast, Russia. It is the List of cities and towns in Russia by population, seventh-largest city in Russia, with a population ...
in the southern Urals region of Russia on February 15, 2013, injuring an estimated 1,500 people with flying glass from broken windows, was an Apollo-class
asteroid
An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
.
List
The largest known Apollo asteroid is
1866 Sisyphus
1866 Sisyphus is a binary stony asteroid, near-Earth object and the largest member of the Apollo group, approximately 7 kilometers in diameter.
It was discovered on 5 December 1972, by Swiss astronomer Paul Wild at Zimmerwald Observatory n ...
, with a diameter of about 8.5 km. Examples of known Apollo asteroids include:
See also
*
Alinda group
*
Amor asteroid
The 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 ...
*
Apollo asteroids (category)
*
Apollo asteroid records
*
Aten asteroid
*
List of minor planets
The following is a list of minor planets in ascending numerical order. Minor planets are Small Solar System bodies, small bodies in the Solar System: asteroids, Distant minor planet, distant objects, and dwarf planets, but not comets. As of 2022 ...
*
2020 PP1
References
External links
List of Apollo minor planets
{{Small Solar System bodies
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 ...