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List Of Minor-planet Groups
A minor-planet group is a population of minor planets that share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid. It is customary to name a group of asteroids after the first member of that group to be discovered, which is often the largest. Groups out to the orbit of Earth There are relatively few asteroids that orbit close to the Sun. Several of these groups are hypothetical at this point in time, with no members having yet been discovered; as such, the names they have been given are provisional. * Vulcanoid asteroids are hypothetical asteroids that orbit entirely within the orbit of Mercury (planet), Mercury (have an aphelion of less than 0.3874 AU). A few searches for vulcanoids have been conducted but none have been discovered so far. * ꞌAylóꞌchaxnim asteroids (previously named Vatira) are asteroids that orbit entirely within the orbit of Venus (have an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 longest semidiameter or one half of the major axis, and thus runs from the centre, through a focus, and to the perimeter. The semi-minor axis (minor semiaxis) of an ellipse or hyperbola is a line segment that is at right angles with the semi-major axis and has one end at the center of the conic section. For the special case of a circle, the lengths of the semi-axes are both equal to the radius of the circle. The length of the semi-major axis of an ellipse is related to the semi-minor axis's length through the eccentricity and the semi-latus rectum \ell, as follows: The semi-major axis of a hyperbola is, depending on the convention, plus or minus one half of the distance between the two branches. Thus it is the distance from the ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Mars-crossing Minor Planets
A Mars-crossing asteroid (MCA, also Mars-crosser, MC) is an asteroid whose orbit crosses that of Mars. Some Mars-crossers numbered below 100000 are listed here. They include the two numbered Mars trojans 5261 Eureka and . Many databases, for instance the JPL Small-Body Database (JPL SBDB), only list asteroids with a perihelion greater than 1.3 AU as Mars-crossers. An asteroid with a perihelion less than this is classed as a near-Earth object even though it is crossing the orbit of Mars as well as crossing (or coming near to) that of Earth. Nevertheless, these objects are listed on this page. A grazer is an object with a perihelion below the aphelion of Mars (1.67 AU) but above the Martian perihelion (1.38 AU). The JPL SBDB lists 13,500 Mars-crossing asteroids. Only 18 MCAs are brighter than absolute magnitude (H) 12.5, which typically makes these asteroids with H<12.5 more than 13 km in diameter depending on the |
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 around the Sun, rather than its current position, thus an object with such an orbit is considered an NEO even at times when it is far from making a close approach of Earth. If an NEO's orbit crosses the Earth's orbit, and the object is larger than across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but about a third of a percent are comets. There are over 37,000 known near-Earth asteroids (NEAs) and over 120 known short-period near-Earth comets (NECs). A number of solar-orbiting meteoroids were large enough to be tracked in space before striking Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of Earth. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Observatory in 1932, the first time that an asteroid was seen to approach Earth so closely. The assumed S-type asteroid is one of few low-numbered asteroids for which no rotation period has been determined. It was assigned the provisional designation ' and named for Cupid, also known as "Amor" in Latin, the Roman equivalent of the Greek god Eros. Discovery On 12 March 1932, Belgian astronomer Eugène Delporte photographed ''Amor'' at the Royal Observatory of Belgium in Uccle, as it approached Earth to within 16 million kilometers (about 40 times the distance from Earth to the Moon). This was the first time that an asteroid was seen to approach Earth so closely. The body's observation arc begins with its official discovery observatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 around the Sun, rather than its current position, thus an object with such an orbit is considered an NEO even at times when it is far from making a close approach of Earth. If an NEO's orbit crosses the Earth's orbit, and the object is larger than across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but about a third of a percent are comets. There are over 37,000 known near-Earth asteroids (NEAs) and over 120 known short-period near-Earth comets (NECs). A number of solar-orbiting meteoroids were large enough to be tracked in space before striking Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of Earth. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lagrangian Point
In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium (mechanics), equilibrium for small-mass objects under the gravity, gravitational influence of two massive orbit, orbiting bodies. Mathematically, this involves the solution of the restricted three-body problem. Normally, the two massive bodies exert an unbalanced gravitational force at a point, altering the orbit of whatever is at that point. At the Lagrange points, the gravitational forces of the two large bodies and the centrifugal force balance each other. This can make Lagrange points an excellent location for satellites, as Orbital station-keeping, orbit corrections, and hence fuel requirements, needed to maintain the desired orbit are kept at a minimum. For any combination of two orbital bodies, there are five Lagrange points, L1 to L5, all in the orbital plane of the two large bodies. There are five Lagrange points for the Sun–Earth system, and five ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth Trojan
An Earth trojan is an asteroid that orbits the Sun in the vicinity of the Earth–Sun Lagrange points (leading 60°) or (trailing 60°), thus having an orbit similar to Earth's. Only two Earth trojans have so far been discovered. The name "trojan" was first used in 1906 for the Jupiter trojans, the asteroids that were observed near the Lagrangian points of Jupiter's orbit. Members (leading) * : A 300-metre diameter asteroid, discovered using the Wide-field Infrared Survey Explorer (WISE) satellite in January 2010. * : Discovered by the Pan-STARRS survey in December 2020 and later recognised as an Earth trojan in January 2021. It is 1.2 km in diameter. (trailing) * No known objects are currently thought to be trojans of Earth. Searches An Earth-based search for objects was conducted in 1994, covering 0.35 square degrees of sky, under poor observing conditions. Received 24 November 1997; revised 13 April 1998. That search fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1991 VG
1991 VG is a very small near-Earth object of the Apollo group, approximately in diameter. It was first observed by American astronomer James Scotti on 6 November 1991, using the Spacewatch telescope on Kitt Peak National Observatory near Tucson, Arizona, in the United States. On 6 December 1991 it passed about from the Moon. The asteroid then went unobserved from April 1992 until it was recovered by Paranal Observatory in May 2017. It was removed from the Sentry Risk Table on 1 June 2017. Discovery and observations On 6 November 1991, Scotti discovered a faint object which was designated 1991 VG soon after discovery. Recovery 1991 VG was not observed between 1992 and 2017. But after 26 years, 1991 VG had returned to the vicinity of Earth. As part of a program by ESA and ESO to secure the orbit of faint but potentially threatening Near-Earth Objects, 1991 VG was recovered by the ESO VLT on 30 May 2017, at magnitude 25. With this recovery, the orbit of 1991 VG is now de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spacewatch
The Spacewatch Project is an astronomical survey that specializes in the study of minor planets, including various types of asteroids and comets at University of Arizona telescopes on Kitt Peak near Tucson, Arizona. The Spacewatch Project has been active longer than any other similar currently active programs. Spacewatch was founded in 1980 by Tom Gehrels and Robert S. McMillan (astronomer), Robert S. McMillan, and is currently led by astronomer Melissa Brucker at the University of Arizona. Spacewatch uses several telescopes on Kitt Peak for follow-up observations of near-Earth objects. The Spacewatch Project uses three telescopes of apertures 0.9-m, 1.8-m, and 2.3-m. These telescopes are located on Kitt Peak, and the first two are dedicated to the purpose of locating Near-Earth object, Near-Earth Objects (NEOs). The 36 inch (0.9 meter) telescope on Kitt Peak has been in use by Spacewatch since 1984, and since 2000 the 72 inch (1.8 meter) Spacewatch telescope. Spacewatch' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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), with most Amors crossing the orbit of Mars. The Amor asteroid 433 Eros was the first asteroid to be orbited and landed upon by a robotic space probe (NEAR Shoemaker). 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. Populations As of January 2025 there are 15,175 known Amor asteroids. Of those objects, 1414 are numbered, 83 are named, a ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arjuna Asteroid
The Arjuna asteroids (also known as "Arjunas") are a dynamical group of asteroids in the Solar System. Arjunas are near-Earth objects (NEOs) whose orbits are very Earth-like in character, having low inclination, orbital periods close to one year, and low eccentricity. The group is named after Arjuna, a central hero in Hindu historic script Mahabharata. The definition is somewhat more relevant and overlaps the definition of the four well-established Apollo, Amor, Aten and Atira groups. They constitute a dynamically cold group of small NEOs that experience repeated trappings in the 1:1 mean-motion resonance with the Earth. Members Potential members of the Arjuna group with their Apollo (APO) or 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 ... (ATE) group classification in pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
