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Distant Minor Planets
A distant minor planet, or ''distant object'', is any minor planet found beyond Jupiter in the outer Solar System that is not commonly thought of as an "asteroid". The umbrella term is used by IAU's Minor Planet Center (MPC), which is responsible for the identification, designation and orbit computation of these objects. , the MPC maintains 6101 distant objects in its data base. Most distant minor planets are trans-Neptunian objects and centaurs, while relatively few are damocloids, Neptune trojans or Uranus trojans. All distant objects have a semi-major axis (average distance from the Sun) greater than 6 AU. This threshold, which is just beyond the orbit of Jupiter (5.2 AU), ensures that the vast majority of "true asteroids" – such as the near-Earth, Mars-crosser, main-belt and Jupiter trojan The Jupiter trojans, commonly called trojan asteroids or simply trojans, are a large group of asteroids that share the planet Jupiter's orbit around the Sun. Relative to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minor Planet
According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor planet'', but that year's meeting IAU definition of planet, reclassified minor planets and comets into dwarf planets and Small Solar System body, small Solar System bodies (SSSBs).Press release, IAU 2006 General Assembly: Result of the IAU Resolution votes International Astronomical Union, August 24, 2006. Accessed May 5, 2008. In contrast to the eight official planets of the Solar System, all minor planets fail to clearing the neighborhood, clear their orbital neighborhood. Minor planets include asteroids (near- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranus Trojan
A Uranus trojan is an asteroid that shares an orbit with Uranus Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant. Most of the planet is made of water, ammonia, and methane in a Supercritical fluid, supercritical phase of matter, which astronomy calls "ice" or Volatile ( ... and the Sun. Predicted in simulations earlier, two trojans have been discovered in Uranus’s Lagrangian point (leading Uranus). was the first body to be classified as such a trojan in 2013, while in 2017 became the second. Several theories have come to be on how such trojans could orbit Uranus. Gravitational scattering is the most popular, stating that such asteroids (or comets) could have been gravitationally pulled by the other planets, leading them on a perfect trajectory towards Uranus, or somewhere where Uranus’s gravitational pull is neutral. References Sources * * Trojans (astronomy) {{asteroid-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical-list Minor Planet
A critical-list minor planet (''critical list numbered object'' or ''critical object'') is a numbered minor planet for which existing measurements of the orbit and position are especially in need of improvement. The IAU's Minor Planet Center (MPC) regularly publishes a list of these critical objects in their ''Minor Planet Electronic Circular''. The list typically contains asteroids that have been observed at a small number of apparitions, especially on opposition, or that have not been adequately observed for more than 10 years, while other observatories create their own, customized lists. The MPC also lists currently observable critical objects on their website, providing differently formatted lists of orbital elements to the worldwide astrometric community. Lowell Observatory publishes their own critical list, distinctly different from the MPC, instead focusing on objects with high ephemeris uncertainty. Specifically, objects with computed ephemeris uncertainty greater than 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jupiter Trojan
The Jupiter trojans, commonly called trojan asteroids or simply trojans, are a large group of asteroids that share the planet Jupiter's orbit around the Sun. Relative to Jupiter, each Trojan (celestial body), trojan Libration point orbit, librates around one of Jupiter's stable Lagrangian point, Lagrange points: either ', existing 60° ahead of the planet in its orbit, or ', 60° behind. Jupiter trojans are distributed in two elongated, curved regions around these Lagrangian points with an average semi-major axis of about 5.2 Astronomical unit, AU. The first Jupiter trojan discovered, 588 Achilles, was spotted in 1906 by German astronomer Max Wolf. More than 9,800 Jupiter trojans have been found . By convention, they are each named from Greek mythology after a figure of the Trojan War, hence the name "trojan". The total number of Jupiter trojans larger than 1 km in diameter is believed to be about , approximately equal to the number of asteroids larger than 1 km in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Main-belt
The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids or minor planets. The identified objects are of many sizes, but much smaller than planets, and, on average, are about one million kilometers (or six hundred thousand miles) apart. This asteroid belt is also called the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System. The asteroid belt is the smallest and innermost circumstellar disc in the Solar System. Classes of small Solar System bodies in other regions are the near-Earth objects, the centaurs, the Kuiper belt objects, the scattered disc objects, the sednoids, and the Oort cloud objects. About 60% of the main belt mass is contained in the four largest asteroids: Ceres, Vesta, Pallas, and Hygiea. The total mass of the asteroid be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mars-crosser
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 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 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 Ea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Unit
The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its modern redefinition in 2012. The astronomical unit is used primarily for measuring distances within the Solar System or around other stars. It is also a fundamental component in the definition of another unit of astronomical length, the parsec. One au is approximately equivalent to 499 light-seconds. History of symbol usage A variety of unit symbols and abbreviations have been in use for the astronomical unit. In a 1976 resolution, the International Astronomical Union (IAU) had used the symbol ''A'' to denote a length equal to the astronomical unit. In the astronomical literature, the symbol AU is common. In 2006, the International Bureau of Weights and Measures (BIPM) had recommended ua as the symbol for the unit, from the French ... [...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] |
Neptune Trojan
Neptune trojans are bodies that orbit the Sun near one of the stable Lagrangian points of Neptune, similar to the trojans of other planets. They therefore have approximately the same orbital period as Neptune and follow roughly the same orbital path. Thirty-one Neptune trojans are currently known, of which 27 orbit near the Sun–Neptune Lagrangian point 60° ahead of Neptune and four orbit near Neptune's region 60° behind Neptune. The Neptune trojans are termed 'trojans' by analogy with the Jupiter trojans. The discovery of in a high-inclination (>25°) orbit was significant, because it suggested a "thick" cloud of trojans ( Jupiter trojans have inclinations up to 40°), which is indicative of freeze-in capture instead of in situ or collisional formation. It is suspected that large (radius ≈ 100 km) Neptune trojans could outnumber Jupiter trojans by an order of magnitude. E. I. Chiang and Y. Lithwick ''Neptune Trojans as a Testbed for Planet Formation'', The Astr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined and slightly less than one-thousandth the mass of the Sun. Its diameter is 11 times that of Earth and a tenth that of the Sun. Jupiter orbits the Sun at a distance of , with an orbital period of . It is the List of brightest natural objects in the sky, third-brightest natural object in the Earth's night sky, after the Moon and Venus, and has been observed since prehistoric times. Its name derives from that of Jupiter (god), Jupiter, the chief deity of ancient Roman religion. Jupiter was the first of the Sun's planets to form, and its inward migration during the primordial phase of the Solar System affected much of the formation history of the other planets. Jupiter's atmosphere consists of 76% hydrogen and 24% helium by mass, with a denser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Damocloid
Damocloids are a class of minor planets such as 5335 Damocles and 1996 PW that have Halley-type or long-period highly eccentric orbits typical of periodic comets such as Halley's Comet, but without showing a cometary coma or tail. David Jewitt defines a damocloid as an object with a Jupiter Tisserand invariant (TJ) of 2 or less, while Akimasa Nakamura defines this group with the following orbital elements: * q 8.0 AU, and e > 0.75, * or alternatively, ''i'' > 90 ° However, this definition that does not focus on Jupiter excludes objects such as , , and . Using the Tisserand's parameter with respect to Jupiter of 2 or less, there are currently 220 damocloid candidates . Of these objects, 189 have orbital observation arcs greater than 30 days providing reasonably decent orbits. Their average radius is eight kilometers assuming an albedo of 0.04. The albedos of four damocloids have been measured, and they are among the darkest objects known in the Solar System. Damoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
