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Quasi-satellite
A quasi-satellite is an object in a specific type of co-orbital configuration (1:1 orbital resonance) with a planet (or dwarf planet) where the object stays close to that planet over many orbital periods. A quasi-satellite's orbit around the Sun takes the same time as the planet's, but has a different eccentricity (usually greater), as shown in the diagram. When viewed from the perspective of the planet by an observer facing the sun, the quasi-satellite will appear to travel in an oblong retrograde loop around the planet. . In contrast to ''true'' satellites, quasi-satellite orbits lie outside the planet's Hill sphere, and are unstable. Over time they tend to evolve to other types of resonant motion, where they no longer remain in the planet's neighborhood, then possibly later move back to a quasi-satellite orbit, etc. Other types of orbit in a 1:1 resonance with the planet include horseshoe orbits and tadpole orbits around the Lagrangian points, but objects in these orbits do not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quasi-satellite Diagram
A quasi-satellite is an object in a specific type of co-orbital configuration (1:1 orbital resonance) with a planet (or dwarf planet) where the object stays close to that planet over many orbital periods. A quasi-satellite's orbit around the Sun takes the same time as the planet's, but has a different eccentricity (usually greater), as shown in the diagram. When viewed from the perspective of the planet by an observer facing the sun, the quasi-satellite will appear to travel in an oblong retrograde loop around the planet. . In contrast to ''true'' satellites, quasi-satellite orbits lie outside the planet's Hill sphere, and are unstable. Over time they tend to evolve to other types of resonant motion, where they no longer remain in the planet's neighborhood, then possibly later move back to a quasi-satellite orbit, etc. Other types of orbit in a 1:1 resonance with the planet include horseshoe orbits and tadpole orbits around the Lagrangian points, but objects in these orbits do ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
469219 Kamoʻoalewa
469219 Kamoʻoalewa (), provisionally designated , is a very small asteroid, fast rotator and near-Earth object of the Apollo group, approximately in diameter. At present it is a quasi-satellite of Earth, and currently the smallest, closest, and most stable known such quasi-satellite. The asteroid was discovered by Pan-STARRS at Haleakala Observatory on 27 April 2016. It was named , a Hawaiian word that refers to an oscillating celestial object. The Earth-like orbit and lunar-like silicates may be a result of it being lunar ejecta. Discovery and naming ''Kamoʻoalewa'' was first spotted on 27 April 2016, by the Pan-STARRS 1 asteroid survey telescope on Haleakalā, Hawaii, that is operated by the University of Hawaii's Institute for Astronomy and funded by NASA's Planetary Defense Coordination Office. The name ''Kamoʻoalewa'' is derived from the Hawaiian words ''ka'' 'the', ''moʻo'' 'fragment', referring to it being a piece broken off a larger object, ''a'' 'of', an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Co-orbital Configuration
In astronomy, a co-orbital configuration is a configuration of two or more astronomical objects (such as asteroids, moons, or planets) orbiting at the same, or very similar, distance from their primary, i.e. they are in a 1:1 mean-motion resonance. (or 1:−1 if orbiting in opposite directions). There are several classes of co-orbital objects, depending on their point of libration. The most common and best-known class is the trojan, which librates around one of the two stable Lagrangian points (Trojan points), and , 60° ahead of and behind the larger body respectively. Another class is the horseshoe orbit, in which objects librate around 180° from the larger body. Objects librating around 0° are called quasi-satellites. An exchange orbit occurs when two co-orbital objects are of similar masses and thus exert a non-negligible influence on each other. The objects can exchange semi-major axes or eccentricities when they approach each other. Parameters Orbital parameters that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horseshoe Orbit
In celestial mechanics, a horseshoe orbit is a type of co-orbital motion of a small orbiting body relative to a larger orbiting body. The osculating (instantaneous) orbital period of the smaller body remains very near that of the larger body, and if its orbit is a little more eccentric than that of the larger body, during every period it appears to trace an ellipse around a point on the larger object's orbit. However, the loop is not closed but drifts forward or backward so that the point it circles will appear to move smoothly along the larger body's orbit over a long period of time. When the object approaches the larger body closely at either end of its trajectory, its apparent direction changes. Over an entire cycle the center traces the outline of a horseshoe, with the larger body between the 'horns'. Asteroids in horseshoe orbits with respect to Earth include 54509 YORP, , , and possibly . A broader definition includes 3753 Cruithne, which can be said to be in a compound ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tadpole Orbit
In celestial mechanics, a horseshoe orbit is a type of co-orbital motion of a small orbiting body relative to a larger orbiting body. The osculating (instantaneous) orbital period of the smaller body remains very near that of the larger body, and if its orbit is a little more eccentric than that of the larger body, during every period it appears to trace an ellipse around a point on the larger object's orbit. However, the loop is not closed but drifts forward or backward so that the point it circles will appear to move smoothly along the larger body's orbit over a long period of time. When the object approaches the larger body closely at either end of its trajectory, its apparent direction changes. Over an entire cycle the center traces the outline of a horseshoe, with the larger body between the 'horns'. Asteroids in horseshoe orbits with respect to Earth include 54509 YORP, , , and possibly . A broader definition includes 3753 Cruithne, which can be said to be in a compound ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neptune
Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth, and slightly more massive than its near-twin Uranus. Neptune is denser and physically smaller than Uranus because its greater mass causes more gravitational compression of its atmosphere. It is referred to as one of the solar system's two ice giant planets (the other one being Uranus). Being composed primarily of gases and liquids, it has no well-defined "solid surface". The planet orbits the Sun once every 164.8 years at an average distance of . It is named after the Roman god of the sea and has the astronomical symbol , representing Neptune's trident. Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation. Un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroid2016HO3-SunEarthOrbit
An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. Of the roughly one million known asteroids the greatest number are located between the orbits of Mars and Jupiter, approximately 2 to 4 AU from the Sun, in the main asteroid belt. Asteroids are generally classified to be of three types: C-type, M-type, and S-type. These were named after and are generally identified with carbonaceous, metallic, and silicaceous compositions, respectively. The size of asteroids varies greatly; the largest, Ceres, is almost across and qualifies as a dwarf planet. The total mass of all the asteroids combined is only 3% that of Earth's Moon. The majority of main belt asteroids follow slightly elliptical, stable orbits, revolving in the same direction as the Earth and taking from three to six years to comple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Mercury-crossing Minor Planets
A Mercury crosser is an asteroid whose orbit crosses that of Mercury. The Mercury crossers proper have aphelia outside Mercury's (0.4667 AU) and perihelia inside Mercury's (0.3075 AU), whereas those listed here as outer grazers have perihelia within Mercury's aphelion but not within its perihelion. All have semi-major axes larger than Mercury's, and hence there are no known inner grazers. List Mercury crossers proper have aphelia outside Mercury's (0.4667 AU) and perihelia inside Mercury's (0.3075 AU). , 362 Mercury crossers were known. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
3753 Cruithne
3753 Cruithne is a Q-type, Aten asteroid in orbit around the Sun in 1:1 orbital resonance with Earth, making it a co-orbital object. It is an asteroid that, relative to Earth, orbits the Sun in a bean-shaped orbit that effectively describes a horseshoe, and that can change into a quasi-satellite orbit. Cruithne does not orbit Earth and at times it is on the other side of the Sun, placing Cruithne well outside of Earth's Hill sphere. Its orbit takes it near the orbit of Mercury and outside the orbit of Mars. Cruithne orbits the Sun in about one Earth year, but it takes 770 years for the series to complete a horseshoe-shaped movement around Earth. The name ''Cruithne'' is from Irish and refers to the early Picts (Old Irish: '' Cruthin'') in the '' Annals of Ulster''Cruithne: Asteroid 3753 . Western Washington University ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hill Sphere
The Hill sphere of an astronomical body is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit that lies within the planet's Hill sphere. That moon would, in turn, have a Hill sphere of its own. Any object within that distance would tend to become a satellite of the moon, rather than of the planet itself. One simple view of the extent of the Solar System is the Hill sphere of the Sun with respect to local stars and the galactic nucleus. In more precise terms, the Hill sphere approximates the gravitational sphere of influence of a smaller body in the face of perturbations from a more massive body. It was defined by the American astronomer George William Hill, based on the work of the French astronomer Édouard Roche. In the example to the right, the Earth's Hill sphere extends between the Lagrange points and , which lie along the line of centers of the two bodies. The region of influence of the smaller body i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lunar Distance (astronomy)
The instantaneous Earth–Moon distance, or distance to the Moon, is the distance from the center of Earth to the center of the Moon. Lunar distance (LD or \Delta_), or Earth–Moon characteristic distance, is a unit of measure in astronomy. More technically, it is the semi-major axis of the geocentric lunar orbit. The lunar distance is on average approximately , or 1.28 light-seconds; this is roughly 30 times Earth's diameter or 9.5 times Earth's circumference. A little less than 400 lunar distances make up an astronomical unit. The semi-major axis has a value of . The time-averaged distance between the centers of Earth and the Moon is . The actual distance varies over the course of the orbit of the Moon, from at the perigee to at apogee, resulting in a differential range of . Lunar distance is commonly used to express the distance to near-Earth object encounters. Lunar semi-major axis is an important astronomical datum; the few millimeter precision of the range measureme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phobos Program
Phobos (Greek for "fear") most commonly refers to: * Phobos (moon), a moon of Mars * Phobos (mythology), the Greek god and personification of fear and panic Phobos may also refer to: Comics * Phobos (Marvel Comics) * Phobos (''W.I.T.C.H.''), a character from ''W.I.T.C.H.'' Computer programming * Project Phobos, a Java-based web application environment * A runtime and standard library of D programming language Other uses * ''Phobos'' (album), a 1997 album by Voivod * ''Phobos'' (audio drama), a 2007 audio drama based on ''Doctor Who'' * Phobos (launch platform), a floating launch platform being refit by SpaceX * PHOBOS experiment, a nuclear physics experiment * Phobos program, a Soviet space program of the late 1980s * USS ''Phobos'' (AK-129), a World War II U.S. Navy ''Crater''-class cargo ship * Huitzil or Phobos, a character in the ''Darkstalkers'' game series See also * Phobos Grunt Fobos-Grunt or Phobos-Grunt (russian: link=no, Фобос-Грунт, where ''гр ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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