Apohele asteroid
Encyclopedia
Apohele asteroids, or alternatively Interior-Earth Objects (IEOs) or Atira asteroids, are a subclass of Aten asteroid
s. They have not only their perihelion within Earth
's orbit, but also their aphelion; that is, their entire orbit is within Earth's (which has a perihelion of 0.983 AU
).
The first suspected Apophele was , the first confirmed Apohele was (163693) Atira in 2003. As of March 2010, there are 10 suspected Apoheles, of which seven have been observed in multiple oppositions, and the orbits of two have been determined with sufficient precision to receive a permanent number (see list below); 28 more objects have aphelia shorter than the Earth's aphelion (1.017 AU). The Near Earth Object Surveillance Satellite
is intended to find more.
In great part because of the search methods used to look for asteroids, there are currently no known asteroids with orbits contained within Venus
or Mercury's
(e.g., Vulcanoids
).
There is no standard name for the class. The name Apohele was proposed by the discoverers of , and is the Hawaii
an word for orbit
; it was chosen partially because of its similarity to the words aphelion (apoapsis) and helios. Other authors adopted the designation Inner Earth Objects (IEOs). Still others, following the general practice to name a new class of asteroids for the first recognized member of that class, use the designation Atira asteroids.
Aten asteroid
The Aten asteroids are a group of near-Earth asteroids, named after the first of the group to be discovered . They are defined by having semi-major axes of less than one astronomical unit...
s. They have not only their perihelion within Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's orbit, but also their aphelion; that is, their entire orbit is within Earth's (which has a perihelion of 0.983 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
).
The first suspected Apophele was , the first confirmed Apohele was (163693) Atira in 2003. As of March 2010, there are 10 suspected Apoheles, of which seven have been observed in multiple oppositions, and the orbits of two have been determined with sufficient precision to receive a permanent number (see list below); 28 more objects have aphelia shorter than the Earth's aphelion (1.017 AU). The Near Earth Object Surveillance Satellite
Near Earth Object Surveillance Satellite
The Near Earth Object Surveillance Satellite is a Canadian microsatellite using a 15-cm aperture f/5.88 Maksutov telescope similar to that on the MOST spacecraft, 3-axis stabilized with pointing stability of ~2 arcseconds in a ~100 second exposure...
is intended to find more.
In great part because of the search methods used to look for asteroids, there are currently no known asteroids with orbits contained within Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
or Mercury's
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
(e.g., Vulcanoids
Vulcanoid asteroid
The vulcanoids are a hypothetical population of asteroids that may orbit the Sun in a dynamically stable zone inside the orbit of the planet Mercury. They are named after the hypothetical planet Vulcan, whose existence was disproven in 1915...
).
There is no standard name for the class. The name Apohele was proposed by the discoverers of , and is the Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
an word for orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
; it was chosen partially because of its similarity to the words aphelion (apoapsis) and helios. Other authors adopted the designation Inner Earth Objects (IEOs). Still others, following the general practice to name a new class of asteroids for the first recognized member of that class, use the designation Atira asteroids.
List
List of known and suspected Apoheles as of 12 February 2010.| Name | Perihelion (AU Astronomical unit An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance.... ) |
Semi-major axis Semi-major axis The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape... (AU) |
Aphelion (AU) |
Eccentricity | Inclination Inclination Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit... (°) |
Observations (# of oppositions) |
|---|---|---|---|---|---|---|
| 2 | ||||||
| 3 | ||||||
| 2 | ||||||
| 3 | ||||||
| 1 (2 days) | ||||||
| 2 | ||||||
| 2 | ||||||
| 1 (1 day) | ||||||
| (163693) Atira | 6 | |||||
| 1 (6 days) |