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Sednoid
A sednoid is a trans-Neptunian object with a perihelion well beyond the Kuiper cliff at . Only four objects are known from this population: 90377 Sedna, , 541132 Leleākūhonua (), and , but it is suspected that there are many more. All four have perihelia greater than . These objects lie outside an apparently nearly empty gap in the Solar System and have no significant interaction with the planets. They are usually grouped with the detached objects. Some astronomers, such as Scott Sheppard, consider the sednoids to be inner Oort cloud objects (OCOs), though the Hills cloud, inner Oort cloud, or Hills cloud, was originally predicted to lie beyond 2,000 AU, beyond the aphelia of the three known sednoids. One attempt at a precise definition of sednoids is any body with a Perihelion and aphelion, perihelion greater than and a semi-major axis greater than . However, this definition applies to objects such as , which has a perihelion at 50.02 AU and a semi-major axis of ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sednoid Orbits
A sednoid is a trans-Neptunian object with a perihelion well beyond the Kuiper cliff at . Only four objects are known from this population: 90377 Sedna, , 541132 Leleākūhonua (), and , but it is suspected that there are many more. All four have perihelia greater than . These objects lie outside an apparently nearly empty gap in the Solar System and have no significant interaction with the planets. They are usually grouped with the detached objects. Some astronomers, such as Scott Sheppard, consider the sednoids to be inner Oort cloud objects (OCOs), though the inner Oort cloud, or Hills cloud, was originally predicted to lie beyond 2,000 AU, beyond the aphelia of the three known sednoids. One attempt at a precise definition of sednoids is any body with a perihelion greater than and a semi-major axis greater than . However, this definition applies to objects such as , which has a perihelion at 50.02 AU and a semi-major axis of about 700 AU but it is thought to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sednoid Apparent Magnitudes
A sednoid is a trans-Neptunian object with a perihelion well beyond the Kuiper cliff at . Only four objects are known from this population: 90377 Sedna, , 541132 Leleākūhonua (), and , but it is suspected that there are many more. All four have perihelia greater than . These objects lie outside an apparently nearly empty gap in the Solar System and have no significant interaction with the planets. They are usually grouped with the detached objects. Some astronomers, such as Scott Sheppard, consider the sednoids to be inner Oort cloud objects (OCOs), though the inner Oort cloud, or Hills cloud, was originally predicted to lie beyond 2,000 AU, beyond the aphelia of the three known sednoids. One attempt at a precise definition of sednoids is any body with a perihelion greater than and a semi-major axis greater than . However, this definition applies to objects such as , which has a perihelion at 50.02 AU and a semi-major axis of about 700 AU but it is thought to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
90377 Sedna
Sedna (minor-planet designation 90377 Sedna) is a dwarf planet in the outer reaches of the Solar System that is in the innermost part of its orbit; it is 84 astronomical units (AU), or 1.26×1010 km, from the Sun, almost three times farther than Neptune. Spectroscopy has revealed that Sedna's surface composition is largely a mixture of water, methane, and nitrogen ices with tholins, similar to those of some other trans-Neptunian objects. Its surface is one of the reddest among Solar System objects. Sedna, within estimated uncertainties, is tied with as the largest planetoid not known to have a moon. Sedna's orbit is one of the largest in the Solar System other than those of long-period comets, with its aphelion (farthest distance from the Sun) estimated at 937 AU. This is 31 times Neptune's distance from the Sun, or 5.5 light-days, and well beyond the closest portion of the heliopause, which defines the boundary of interstellar space. As of 2022, the dwarf planets ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
541132 Leleākūhonua
541132 Leleākūhonua (), provisionally designated , is an extreme trans-Neptunian object and sednoid in the outermost part of the Solar System. It was first observed on 13 October 2015, by astronomers at the Mauna Kea Observatories, Hawaii. Based on its discovery date near Halloween and the letters in its provisional designation , the object was informally nicknamed "The Goblin" by its discoverers and later named ''Leleākūhonua'', comparing its orbit to the flight of the Pacific golden plover. It was the third sednoid discovered, after and , and measures around in diameter. Discovery ''Leleākūhonua'' was first observed on 13 October 2015 at the Mauna Kea Observatory , by American astronomers David Tholen, Chad Trujillo and Scott Sheppard during their astronomical survey for objects located beyond the Kuiper Cliff. The unofficial discovery was publicly announced on 1 October 2018. The survey uses two principal telescopes: For the Northern hemisphere, the 8.2-meter Su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Detached Object
Detached objects are a dynamical class of minor planets in the outer reaches of the Solar System and belong to the broader family of trans-Neptunian objects (TNOs). These objects have orbits whose points of closest approach to the Sun (perihelion) are sufficiently distant from the gravitational influence of Neptune that they are only moderately affected by Neptune and the other known planets: This makes them appear to be "detached" from the rest of the Solar System, except for their attraction to the Sun. In this way, detached objects differ substantially from most other known TNOs, which form a loosely defined set of populations that have been perturbed to varying degrees onto their current orbit by gravitational encounters with the giant planets, predominantly Neptune. Detached objects have larger perihelia than these other TNO populations, including the objects in orbital resonance with Neptune, such as Pluto, the classical Kuiper belt objects in non-resonant orbits such as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trans-Neptunian Object
A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has a semi-major axis of 30.1 astronomical units (au). Typically, TNOs are further divided into the classical and resonant objects of the Kuiper belt, the scattered disc and detached objects with the sednoids being the most distant ones. As of October 2020, the catalog of minor planets contains 678 numbered and more than 2,000 unnumbered TNOs. The first trans-Neptunian object to be discovered was Pluto in 1930. It took until 1992 to discover a second trans-Neptunian object orbiting the Sun directly, 15760 Albion. The most massive TNO known is Eris, followed by Pluto, , , and . More than 80 satellites have been discovered in orbit of trans-Neptunian objects. TNOs vary in color and are either grey-blue (BB) or very red (RR). They are thought to be composed of mixtures of rock, amorphous carbon and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planet Nine
Planet Nine is a hypothetical planet in the outer region of the Solar System. Its gravitational effects could explain the peculiar clustering of orbits for a group of extreme trans-Neptunian objects (ETNOs), bodies beyond Neptune that orbit the Sun at distances averaging more than 250 times that of the Earth. These ETNOs tend to make their closest approaches to the Sun in one sector, and their orbits are similarly tilted. These alignments suggest that an undiscovered planet may be shepherding the orbits of the most distant known Solar System objects. Nonetheless, some astronomers question this conclusion and instead assert that the clustering of the ETNOs orbits is due to observational biases, resulting from the difficulty of discovering and tracking these objects during much of the year. Based on earlier considerations, this hypothetical super-Earth-sized planet would have had a predicted mass of five to ten times that of the Earth, and an elongated orbit 400 to 800 times as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hills Cloud
In astronomy, the Hills cloud (also called the inner Oort cloud and inner cloud) is a vast theoretical circumstellar disc, interior to the Oort cloud, whose outer border would be located at around 20,000 to 30,000 astronomical units (AU) from the Sun, and whose inner border, less well defined, is hypothetically located at , well beyond planetary and Kuiper Belt object orbits—but distances might be much greater. If it exists, the Hills cloud contains roughly 5 times as many comets as the Oort cloud. Overview The need for the Hills cloud hypothesis is intimately connected with the dynamics of the Oort cloud: Oort cloud comets are continually perturbed in their environment. A non-negligible fraction leave the Solar System, or tumble into the inner system where they evaporate, or fall into the Sun or gas giants. Hence, the Oort cloud should have been depleted long ago, but it is still well supplied with comets. The Hills cloud hypothesis addresses the persistence of the O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
474640 Alicanto
474640 Alicanto, Provisional designation in astronomy, provisionally designated , is a detached object, detached extreme trans-Neptunian object. It was discovered on 6 November 2004, by American astronomer Andrew C. Becker at Cerro Tololo Inter-American Observatory in Chile. It never gets closer than 47 AU from the Sun (near the outer edge of the main Kuiper belt) and averages more than 300 AU from the Sun. Its large Orbital eccentricity, eccentricity strongly suggests that it was gravitationally scattered onto its current orbit. Because it is, like all detached objects, outside the current gravitational influence of Neptune, how it came to have this orbit cannot yet be explained. It was named after Alicanto, a nocturnal bird in Chilean mythology. Discovery and orbit ''Alicanto'' was discovered by American astronomer Andrew C. Becker, A. C. Becker with the ESSENCE supernova survey on 6 November 2004 observing with the 4-meter Blanco Telescope from Cerro Tololo Inter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semimajor 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 center t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Argument Of Perihelion
The argument of periapsis (also called argument of perifocus or argument of pericenter), symbolized as ''ω'', is one of the orbital elements of an orbiting body. Parametrically, ''ω'' is the angle from the body's ascending node to its periapsis, measured in the direction of motion. For specific types of orbits, terms such as argument of perihelion (for heliocentric orbits), argument of perigee (for geocentric orbits), argument of periastron (for orbits around stars), and so on, may be used (see apsis for more information). An argument of periapsis of 0° means that the orbiting body will be at its closest approach to the central body at the same moment that it crosses the plane of reference from South to North. An argument of periapsis of 90° means that the orbiting body will reach periapsis at its northmost distance from the plane of reference. Adding the argument of periapsis to the longitude of the ascending node gives the longitude of the periapsis. However, especially ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minor Planet Center
The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function The Minor Planet Center is the official worldwide organization in charge of collecting observational data for minor planets (such as asteroids), calculating their orbits and publishing this information via the '' Minor Planet Circulars''. Under the auspices of the International Astronomical Union (IAU), it operates at the Smithsonian Astrophysical Observatory, which is part of the Center for Astrophysics along with the Harvard College Observatory. The MPC runs a number of free online services for observers to assist them in observing minor planets and comets. The complete catalogue of minor planet orbits (sometimes referred to as the "Minor Planet Catalogue") may also be freely downloaded. In addition to astrometric data, the MPC collect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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