1.
Neptune
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Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the planet. Neptune is 17 times the mass of Earth and is more massive than its near-twin Uranus. Neptune orbits the Sun once every 164.8 years at a distance of 30.1 astronomical units. It is named after the Roman god of the sea and has the astronomical symbol ♆, 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. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to perturbation by an unknown planet. Neptune was subsequently observed with a telescope on 23 September 1846 by Johann Galle within a degree of the predicted by Urbain Le Verrier. Its largest moon, Triton, was discovered shortly thereafter, though none of the remaining known 14 moons were located telescopically until the 20th century. The planets distance from Earth gives it a small apparent size. Neptune was visited by Voyager 2, when it flew by the planet on 25 August 1989, the advent of the Hubble Space Telescope and large ground-based telescopes with adaptive optics has recently allowed for additional detailed observations from afar. Neptunes composition can be compared and contrasted with the Solar Systems other giant planets, however, its interior, like that of Uranus, is primarily composed of ices and rock, which is why Uranus and Neptune are normally considered ice giants to emphasise this distinction. Traces of methane in the outermost regions in part account for the blue appearance. In contrast to the hazy, relatively featureless atmosphere of Uranus, Neptunes atmosphere has active, for example, at the time of the Voyager 2 flyby in 1989, the planets southern hemisphere had a Great Dark Spot comparable to the Great Red Spot on Jupiter. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, because of its great distance from the Sun, Neptunes outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching 55 K. Temperatures at the centre are approximately 5,400 K. Neptune has a faint and fragmented ring system. On both occasions, Galileo seems to have mistaken Neptune for a star when it appeared close—in conjunction—to Jupiter in the night sky, hence. At his first observation in December 1612, Neptune was almost stationary in the sky because it had just turned retrograde that day and this apparent backward motion is created when Earths orbit takes it past an outer planet. Because Neptune was only beginning its yearly cycle, the motion of the planet was far too slight to be detected with Galileos small telescope
2.
Pluto
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Pluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered, Pluto was discovered by Clyde Tombaugh in 1930 and was originally considered to be the ninth planet from the Sun. After 1992, its planethood was questioned following the discovery of objects of similar size in the Kuiper belt. In 2005, Eris, which is 27% more massive than Pluto, was discovered and this led the International Astronomical Union to define the term planet formally in 2006, during their 26th General Assembly. That definition excluded Pluto and reclassified it as a dwarf planet, Pluto is the largest and second-most-massive known dwarf planet in the Solar System and the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but is less massive than Eris, like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—about one-sixth the mass of the Moon and one-third its volume. It has an eccentric and inclined orbit during which it ranges from 30 to 49 astronomical units or AU from the Sun. This means that Pluto periodically comes closer to the Sun than Neptune, light from the Sun takes about 5.5 hours to reach Pluto at its average distance. Pluto has five moons, Charon, Styx, Nix, Kerberos. Pluto and Charon are sometimes considered a system because the barycenter of their orbits does not lie within either body. The IAU has not formalized a definition for binary dwarf planets, on July 14,2015, the New Horizons spacecraft became the first spacecraft to fly by Pluto. During its brief flyby, New Horizons made detailed measurements and observations of Pluto, on October 25,2016, at 05,48 pm ET, the last bit of data was received from New Horizons from its close encounter with Pluto on July 14,2015. In the 1840s, Urbain Le Verrier used Newtonian mechanics to predict the position of the then-undiscovered planet Neptune after analysing perturbations in the orbit of Uranus. Subsequent observations of Neptune in the late 19th century led astronomers to speculate that Uranuss orbit was being disturbed by another planet besides Neptune, by 1909, Lowell and William H. Pickering had suggested several possible celestial coordinates for such a planet. Lowell and his observatory conducted his search until his death in 1916, unknown to Lowell, his surveys had captured two faint images of Pluto on March 19 and April 7,1915, but they were not recognized for what they were. There are fourteen other known prediscovery observations, with the oldest made by the Yerkes Observatory on August 20,1909. Percivals widow, Constance Lowell, entered into a legal battle with the Lowell Observatory over her late husbands legacy. Tombaughs task was to image the night sky in pairs of photographs, then examine each pair
3.
Centaur (minor planet)
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Centaurs are minor planets with a semi-major axis between those of the outer planets. They have unstable orbits that cross or have crossed the orbits of one or more of the giant planets, Centaurs typically behave with characteristics of both asteroids and comets. They are named after the centaurs that were a mixture of horse. It has been estimated there are around 44,000 centaurs in the Solar System with diameters larger than 1 km. The first centaur to be discovered, under the definition of the Jet Propulsion Laboratory, however, they were not recognized as a distinct population until the discovery of 2060 Chiron in 1977. The largest confirmed centaur is 10199 Chariklo, which at 260 km in diameter is as big as a mid-sized main-belt asteroid, however, the lost centaur 1995 SN55 may be somewhat larger. No centaur has been photographed up close, although there is evidence that Saturns moon Phoebe, imaged by the Cassini probe in 2004, in addition, the Hubble Space Telescope has gleaned some information about the surface features of 8405 Asbolus. As of 2008, three centaurs have been found to display comet-like comas, Chiron,60558 Echeclus, and 166P/NEAT, Chiron and Echeclus are therefore classified as both asteroids and comets. Other centaurs, such as 52872 Okyrhoe and 2012 CG, are suspected of having shown comas, any centaur that is perturbed close enough to the Sun is expected to become a comet. The generic definition of a centaur is a body that orbits the Sun between Jupiter and Neptune and crosses the orbits of one or more of the giant planets. Though nowadays the MPC often lists centaurs and scattered disc objects together as a single group, the Jet Propulsion Laboratory similarly defines centaurs as having a semi-major axis, a, between those of Jupiter and Neptune. In contrast, the Deep Ecliptic Survey defines centaurs using a classification scheme. These classifications are based on the change in behavior of the present orbit when extended over 10 million years. The DES defines centaurs as non-resonant objects whose instantaneous perihelia are less than the osculating semi-major axis of Neptune at any time during the simulation and this definition is intended to be synonymous with planet-crossing orbits and to suggest comparatively short lifetimes in the current orbit. The collection The Solar System Beyond Neptune defines objects with an axis between those of Jupiter and Neptune and a Jupiter – Tisserands parameter above 3. The JPL Small-Body Database lists 324 centaurs, there are an additional 65 trans-Neptunian objects with a perihelion closer than the orbit of Uranus. The Committee on Small Body Nomenclature of the International Astronomical Union has not formally weighed in on either side of the debate, thus far, only the binary objects Ceto and Phorcys and Typhon and Echidna have been named according to the new policy. Other objects caught between these differences in classification methods include 944 Hidalgo which was discovered in 1920 and is listed as a centaur in the JPL Small-Body Database
4.
Neptune trojan
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Neptune trojans are bodies in orbit around the Sun that orbit near one of the stable Lagrangian points of Neptune. They therefore have approximately the same period as Neptune and follow roughly the same orbital path. Seventeen Neptune trojans are known, of which thirteen orbit near the Sun–Neptune L4 Lagrangian point 60° ahead of Neptune. The Neptune trojans are termed trojans by analogy with the Jupiter trojans and it is suspected that large Neptune trojans could outnumber Jupiter trojans by an order of magnitude. In 2010, the discovery of the first known L5 Neptune trojan,2008 LC18, was announced, Neptunes trailing L5 region is currently very difficult to observe because it is along the line-of-sight to the center of the Milky Way, an area of the sky crowded with stars. However, New Horizons may not have had sufficient downlink bandwidth, in 2001, the first Neptune trojan was discovered,2001 QR322, near Neptunes L4 region, and with it the fifth known populated stable reservoir of small bodies in the Solar System. In 2005, the discovery of the high-inclination trojan 2005 TN53 has indicated that the Neptune trojans populate thick clouds, on August 12,2010, the first L5 trojan,2008 LC18, was announced. It was discovered by a survey that scanned regions where the light from the stars near the Galactic Center is obscured by dust clouds. This suggests that large L5 trojans are as common as large L4 trojans, to within uncertainty and it would have been possible for the New Horizons spacecraft to investigate L5 Neptune trojans discovered by 2014, when it passed through this region of space en route to Pluto. Some of the patches where the light from the Galactic Center is obscured by dust clouds are along New Horizonss flight path, allowing detection of objects that the spacecraft could image. 2011 HM102, the highest-inclination Neptune trojan known, was just bright enough for New Horizons to observe it in end-2013 at a distance of 1.2 AU. However, New Horizons may not have had sufficient downlink bandwidth, the orbits of Neptune trojans are highly stable, Neptune may have retained up to 50% of the original post-migration trojan population over the age of the Solar System. Neptunes L5 can host stable trojans equally well as its L4, Neptune trojans can librate up to 30° from their associated Lagrangian points with a 10, 000-year period. Neptune trojans that escape enter orbits similar to centaurs, although Neptune cannot currently capture stable trojans, roughly 2. 8% of the centaurs within 34 AU are predicted to be Neptune co-orbitals. Of these, 54% would be in horseshoe orbits, 10% would be quasi-satellites, the unexpected high-inclination trojans are the key to understanding the origin and evolution of the population as a whole. The existence of high-inclination Neptune trojans points to a capture during planetary migration instead of in situ or collisional formation. The estimated equal number of large L5 and L4 trojans indicates that there was no gas drag during capture, the capture of Neptune trojans during a migration of the planets occurs via process similar to the chaotic capture of Jupiter trojans in the Nice model. When Uranus and Neptune are near but not in a mean-motion resonance the period at which the locations where Uranus passes Neptune circulate can resonate with the periods of Neptune trojans
5.
Trans-Neptunian object
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A trans-Neptunian object is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune,30 astronomical units. Twelve minor planets with a semi-major axis greater than 150 AU and perihelion greater than 30 AU are known, 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,1992 QB1, as of February 2017 over 2,300 trans-Neptunian objects appear on the Minor Planet Centers List of Transneptunian Objects. Of these TNOs,2,000 have a perihelion farther out than Neptune, as of November 2016,242 of these have their orbits well-enough determined that they have been given a permanent minor planet designation. The largest known object is Pluto, followed by Eris,2007 OR10, Makemake. The Kuiper belt, scattered disk, and Oort cloud are three divisions of this volume of space, though treatments vary and a few objects such as Sedna do not fit easily into any division. The orbit of each of the planets is slightly affected by the influences of the other planets. Discrepancies in the early 1900s between the observed and expected orbits of Uranus and Neptune suggested that there were one or more additional planets beyond Neptune, the search for these led to the discovery of Pluto in February 1930, which was too small to explain the discrepancies. Revised estimates of Neptunes mass from the Voyager 2 flyby in 1989 showed that the problem was spurious, Pluto was easiest to find because it has the highest apparent magnitude of all known trans-Neptunian objects. It also has an inclination to the ecliptic than most other large TNOs. After Plutos discovery, American astronomer Clyde Tombaugh continued searching for years for similar objects. For a long time, no one searched for other TNOs as it was believed that Pluto. Only after the 1992 discovery of a second TNO,1992 QB1, a broad strip of the sky around the ecliptic was photographed and digitally evaluated for slowly moving objects. Hundreds of TNOs were found, with diameters in the range of 50 to 2,500 kilometers, Pluto and Eris were eventually classified as dwarf planets by the International Astronomical Union. Kuiper belt objects are classified into the following two groups, Resonant objects are locked in an orbital resonance with Neptune. Objects with a 1,2 resonance are called twotinos, and objects with a 2,3 resonance are called plutinos, after their most prominent member, classical Kuiper belt objects have no such resonance, moving on almost circular orbits, unperturbed by Neptune. Examples are 1992 QB1,50000 Quaoar and Makemake, the scattered disc contains objects farther from the Sun, usually with very irregular orbits. A typical example is the most massive known TNO, Eris, scattered-extended —Scattered-extended objects have a Tisserand parameter greater than 3 and have a time-averaged eccentricity greater than 0
6.
Kuiper belt
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It is similar to the asteroid belt, but it is far larger—20 times as wide and 20 to 200 times as massive. Like the asteroid belt, it consists mainly of small bodies, although many asteroids are composed primarily of rock and metal, most Kuiper belt objects are composed largely of frozen volatiles, such as methane, ammonia and water. The Kuiper belt is home to three officially recognized dwarf planets, Pluto, Haumea, and Makemake, some of the Solar Systems moons, such as Neptunes Triton and Saturns Phoebe, are also thought to have originated in the region. The Kuiper belt was named after Dutch-American astronomer Gerard Kuiper, though he did not actually predict its existence, in 1992,1992 QB1 was discovered, the first Kuiper belt object since Pluto. Since its discovery, the number of known KBOs has increased to over a thousand, the Kuiper belt should not be confused with the theorized Oort cloud, which is a thousand times more distant and is mostly spherical. The objects within the Kuiper belt, together with the members of the scattered disc, Pluto is the largest and most-massive member of the Kuiper belt and the largest and the second-most-massive known TNO, surpassed only by Eris in the scattered disc. Originally considered a planet, Plutos status as part of the Kuiper belt caused it to be reclassified as a planet in 2006. It is compositionally similar to other objects of the Kuiper belt, and its orbital period is characteristic of a class of KBOs, known as plutinos. After the discovery of Pluto in 1930, many speculated that it not be alone. The region now called the Kuiper belt was hypothesized in various forms for decades and it was only in 1992 that the first direct evidence for its existence was found. The number and variety of speculations on the nature of the Kuiper belt have led to continued uncertainty as to who deserves credit for first proposing it. The first astronomer to suggest the existence of a population was Frederick C. That same year, astronomer Armin O. Leuschner suggested that Pluto may be one of many long-period planetary objects yet to be discovered. Kuiper was operating on the common in his time that Pluto was the size of Earth and had therefore scattered these bodies out toward the Oort cloud or out of the Solar System. Were Kuipers hypothesis correct, there would not be a Kuiper belt today, the hypothesis took many other forms in the following decades. Cameron postulated the existence of a mass of small material on the outskirts of the solar system. Observation, however, ruled out this hypothesis, in 1977, Charles Kowal discovered 2060 Chiron, an icy planetoid with an orbit between Saturn and Uranus. He used a blink comparator, the device that had allowed Clyde Tombaugh to discover Pluto nearly 50 years before
7.
Resonant trans-Neptunian object
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In astronomy, a resonant trans-Neptunian object is a trans-Neptunian object in mean-motion orbital resonance with Neptune. The orbital periods of the resonant objects are in a simple integer relations with the period of Neptune e. g.1,2,2,3 etc, resonant TNOs can be either part of the main Kuiper belt population, or the more distant scattered disc population. The diagram illustrates the distribution of the known trans-Neptunian objects, resonant objects are plotted in red. The designation 2,3 or 3,2 both refer to the resonance for TNOs. There is no ambiguity, because TNOs have, by definition, the usage depends on the author and the field of research. Detailed analytical and numerical studies of Neptune’s resonances have shown that the objects must have a precise range of energies. If the objects semi-major axis is outside these ranges, the orbit becomes chaotic. As TNOs were discovered, more than 10% were found to be in 2,3 resonances and it is now believed that the objects have been collected from wider distances by sweeping resonances during the migration of Neptune. During this relatively short period of time, Neptunes resonances would be sweeping the space, the 2,3 resonance at 39.4 AU is by far the dominant category among the resonant objects, with 92 confirmed and 104 possible member bodies. The objects following orbits in this resonance are named plutinos after Pluto, the objects are rather small and most of them follow orbits close to the ecliptic. Twotinos have inclinations less than 15 degrees and generally moderate eccentricities, there are far fewer objects in this resonance than plutinos. Consequently, it might be that twotinos were originally as numerous as plutinos and these Neptune trojans, termed by analogy to the Trojan asteroids, are in 1,1 resonance with Neptune. One of the concerns is that weak resonances may exist and would be difficult to due to the current lack of accuracy in the orbits of these distant objects. Many objects have orbital periods of more than 300 years and most have only observed over a short observation arc of a couple years. A true resonance will smoothly oscillate while a coincidental near resonance will circulate, simulations by Emel’yanenko and Kiseleva in 2007 show that 2001 XT254 is librating in a 3,7 resonance with Neptune. This libration can be stable for less than 100 million to billions of years, Emel’yanenko and Kiseleva also show that 1995 TL8 appears to have less than a 1% probability of being in a 3,7 resonance with Neptune, but it does execute circulations near this resonance. The classes of TNO have no universally agreed definitions, the boundaries are often unclear. The Deep Ecliptic Survey introduced formally defined dynamical classes based on long-term forward integration of orbits under the combined perturbations from all four giant planets
8.
Plutino
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In astronomy, a plutino is a trans-Neptunian object in 2,3 mean-motion resonance with Neptune. For every 2 orbits that a plutino makes, Neptune orbits 3 times, the term plutino derived from the dwarf planet Pluto, the largest and the first plutino discovered. The term does not imply common physical characteristics, Plutinos are named after mythological creatures associated with the underworld. Plutinos form the part of the Kuiper belt and represent about a quarter of the known Kuiper belt objects. Plutinos are the largest class of the resonant trans-Neptunian objects, aside from Pluto itself, the first plutino,1993 RO, was discovered on September 16,1993. It is thought that objects that are currently in mean orbital resonances with Neptune initially followed independent heliocentric paths. As Neptune migrated outward early in the Solar Systems history, the bodies it approached would have been scattered, during this process, the 3,2 resonance is the strongest and most stable among all resonances. This is the reason it contains the largest number of bodies. The orbital periods of plutinos cluster around 247.3 years, the gravitational influence of Pluto is usually neglected given its small mass. However, the width is very narrow and only a few times larger than Pluto’s Hill sphere. Consequently, depending on the eccentricity, some plutinos will be driven out of the resonance by interactions with Pluto. Numerical simulations suggest that the orbits of plutinos with an eccentricity 10%–30% smaller or larger than that of Pluto are not stable over Ga timescales, the plutinos brighter than HV=6 include, David Jewitt on Plutinos Minor Planet Center, List of TNOs MPC List of Distant Minor Planets
9.
Scattered disc
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The scattered disc is a distant circumstellar disc in the Solar System that is sparsely populated by icy minor planets, a subset of the broader family of trans-Neptunian objects. The scattered-disc objects have orbital eccentricities ranging as high as 0.8, inclinations as high as 40° and these extreme orbits are thought to be the result of gravitational scattering by the gas giants, and the objects continue to be subject to perturbation by the planet Neptune. Although the closest scattered-disc objects approach the Sun at about 30–35 AU and this makes scattered objects among the most distant and coldest objects in the Solar System. Eventually, perturbations from the giant planets send such objects towards the Sun, many Oort cloud objects are also thought to have originated in the scattered disc. Detached objects are not sharply distinct from scattered disc objects, during the 1980s, the use of CCD-based cameras in telescopes made it possible to directly produce electronic images that could then be readily digitized and transferred to digital images. Because the CCD captured more light than film and the blinking could now be done at a computer screen. A flood of new discoveries was the result, over a thousand objects were detected between 1992 and 2006. The first scattered-disc object to be recognised as such was 1996 TL66, three more were identified by the same survey in 1999,1999 CV118,1999 CY118, and 1999 CF119. The first object presently classified as an SDO to be discovered was 1995 TL8, as of 2011, over 200 SDOs have been identified, including 2007 UK126,2002 TC302, Eris, Sedna and 2004 VN112. Known trans-Neptunian objects are divided into two subpopulations, the Kuiper belt and the scattered disc. A third reservoir of trans-Neptunian objects, the Oort cloud, has been hypothesized, some researchers further suggest a transitional space between the scattered disc and the inner Oort cloud, populated with detached objects. Those in 3,2 resonances are known as plutinos, because Pluto is the largest member of their group, in contrast to the Kuiper belt, the scattered-disc population can be disturbed by Neptune. Scattered-disc objects come within range of Neptune at their closest approaches. Some objects, like 1999 TD10, blur the distinction and the Minor Planet Center, the MPC also makes a clear distinction between the Kuiper belt and the scattered disc, separating those objects in stable orbits from those in scattered orbits. Another term used is scattered Kuiper-belt object for bodies of the scattered disc and this delineation is inadequate over the age of the Solar System, since bodies trapped in resonances could pass from a scattering phase to a non-scattering phase numerous times. That is, trans-Neptunian objects could travel back and forth between the Kuiper belt and the disc over time. In the a >30 AU region, the region of the Solar System populated by objects with semi-major axes greater than 30 AU, the Minor Planet Center classifies the trans-Neptunian object 90377 Sedna as a scattered-disc object. Under this definition, an object with a greater than 40 AU could be classified as outside the scattered disc
10.
Detached object
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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. This reflects the dynamical gradation that can exist between the parameters of the scattered disk and the detached population. At least nine such bodies have been identified, of which the largest, most distant. Those with perihelia greater than 75 AU are termed sednoids, as of 2016, there are two known sednoids, Sedna and 2012 VP113. Detached objects have much larger than Neptunes aphelion. They often have highly elliptical, very large orbits with semi-major axes of up to a few hundred astronomical units, such orbits cannot have been created by gravitational scattering by the giant planets. Instead, a number of explanations have been put forward, including an encounter with a star or a distant planet-sized object. The classification suggested by the Deep Ecliptic Survey team introduces a distinction between scattered-near objects and scattered-extended objects using a Tisserands parameter value of 3. Detached objects are one of five distinct classes of TNO, the other four classes are classical Kuiper-belt objects, resonant objects, scattered-disc objects. Detached objects generally have a distance greater than 40 AU, deterring strong interactions with Neptune. However, there are no boundaries between the scattered and detached regions, since both can coexist as TNOs in an intermediate region with perihelion distance between 37 and 40 AU. One such intermediate body with a well determined orbit is 2003 FY128, although Sedna is officially considered a scattered-disc object by the MPC, its discoverer Michael E. This classification of Sedna as an object is accepted in recent publications. They have orbital periods of more than 300 years and most have only observed over a short observation arc of a couple years. Further improvement in the orbit and potential resonance of objects will help to understand the migration of the giant planets. For example, simulations by Emel’yanenko and Kiseleva in 2007 show that many distant objects could be in resonance with Neptune. They show a 10% likelihood that 2000 CR105 is in a 20,1 resonance, a 38% likelihood that 2003 QK91 is in a 10,3 resonance, and an 84% likelihood that 2000 YW134 is in an 8,3 resonance. The likely dwarf planet 2005 TB190 appears to have less than a 1% likelihood of being in a 4,1 resonance
11.
Sednoid
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A sednoid is a trans-Neptunian object with a perihelion greater than 50 AU and a semi-major axis greater than 150 AU. Only two objects are known from this population,90377 Sedna and 2012 VP113, both of which have greater than 75 AU, but it is suspected that there are many more. These objects lie outside an apparently nearly empty gap in the Solar System starting at about 50 AU and they are usually grouped with the detached objects. The sednoids orbits cannot be explained by perturbations from the giant planets and their orbits could have been disrupted by an as-yet-unknown planet-sized body beyond the Kuiper belt such as the hypothesized Planet Nine. They could have captured from around passing stars, most likely in the Suns birth cluster. The two sednoids, like all of the more extreme detached objects, have an orientation of ≈ 0°.5 Gyr for Sedna. This suggests that one or more undiscovered massive perturbers may exist in the outer Solar System, a super-Earth at 250 AU would cause these objects to librate around ω = 0°±60° for billions of years. There are multiple possible configurations and a low-albedo super-Earth at that distance would have an apparent magnitude below the current all-sky-survey detection limits and this hypothetical super-Earth has been dubbed Telisto and Planet Nine. Larger, more-distant perturbers would also be too faint to be detected, fourteen known objects have a semi-major axis greater than 150 AU, a perihelion beyond Neptune, an argument of perihelion of 340°±55°, and an observation arc of more than 1 year. Each of the mechanisms for Sednas extreme orbit would leave a distinct mark on the structure. If a trans-Neptunian planet was responsible, all such objects would share roughly the same perihelion, if it rotated in the opposite direction, then two populations would form, one with low and one with high inclinations. The perturbations from passing stars would produce a variety of perihelia and inclinations, each dependent on the number. Acquiring a larger sample of objects would therefore help in determining which scenario is most likely. I call Sedna a fossil record of the earliest Solar System, eventually, when other fossil records are found, Sedna will help tell us how the Sun formed and the number of stars that were close to the Sun when it formed. A 2007–2008 survey by Brown, Rabinowitz and Schwamb attempted to locate another member of Sednas hypothetical population, although the survey was sensitive to movement out to 1,000 AU and discovered the likely dwarf planet 2007 OR10, it detected no new sednoids. Subsequent simulations incorporating the new data suggested about 40 Sedna-sized objects probably exist in this region, new icy body hints at planet lurking beyond Pluto
12.
Oort cloud
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The Oort cloud, sometimes called the Öpik–Oort cloud, is a theoretical cloud of predominantly icy planetesimals believed to surround the Sun to as far as somewhere between 50,000 and 200,000 AU. It is divided into two regions, a disc-shaped inner Oort cloud and a spherical outer Oort cloud, both regions lie beyond the heliosphere and in interstellar space. The Kuiper belt and the disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth as far from the Sun as the Oort cloud. The outer limit of the Oort cloud defines the boundary of the Solar System. The outer Oort cloud is only bound to the Solar System. These forces occasionally dislodge comets from their orbits within the cloud, based on their orbits, most of the short-period comets may come from the scattered disc, but some may still have originated from the Oort cloud. In 1932, the Estonian astronomer Ernst Öpik postulated that long-period comets originated in a cloud at the outermost edge of the Solar System. The idea was revived by Dutch astronomer Jan Oort as a means to resolve a paradox. Thus, Oort reasoned, a comet could not have formed while in its current orbit, there are two main classes of comet, short-period comets and long-period comets. Ecliptic comets have relatively small orbits, below 10 AU, and follow the ecliptic plane, all long-period comets have very large orbits, on the order of thousands of AU, and appear from every direction in the sky. Oort noted that there was a peak in numbers of comets with aphelia of roughly 20,000 AU. The Oort cloud is thought to occupy a vast space from somewhere between 2,000 and 5,000 AU to as far as 50,000 AU from the Sun, some estimates place the outer edge at between 100,000 and 200,000 AU. The region can be subdivided into a spherical outer Oort cloud of 20, 000–50,000 AU, the outer cloud is only weakly bound to the Sun and supplies the long-period comets to inside the orbit of Neptune. The inner Oort cloud is known as the Hills cloud, named after Jack G. Hills. The Hills cloud explains the existence of the Oort cloud after billions of years. The outer Oort cloud may have trillions of objects larger than 1 km, earlier it was thought to be more massive, but improved knowledge of the size distribution of long-period comets led to lower estimates. The mass of the inner Oort cloud has not been characterized, if analyses of comets are representative of the whole, the vast majority of Oort-cloud objects consist of ices such as water, methane, ethane, carbon monoxide and hydrogen cyanide. The Oort cloud is thought to be a remnant of the protoplanetary disc that formed around the Sun approximately 4.6 billion years ago
13.
Dwarf planet
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A dwarf planet is a planetary-mass object that is neither a planet nor a natural satellite. The International Astronomical Union currently recognizes five dwarf planets, Ceres, Pluto, Haumea, Makemake, another hundred or so known objects in the Solar System are suspected to be dwarf planets. Individual astronomers recognize several of these, and in August 2011 Mike Brown published a list of 390 candidate objects, Stern states that there are more than a dozen known dwarf planets. Only two of these bodies, Ceres and Pluto, have observed in enough detail to demonstrate that they actually fit the IAUs definition. The IAU accepted Eris as a dwarf planet because it is more massive than Pluto and they subsequently decided that unnamed trans-Neptunian objects with an absolute magnitude brighter than +1 are to be named under the assumption that they are dwarf planets. The classification of bodies in other systems with the characteristics of dwarf planets has not been addressed. Starting in 1801, astronomers discovered Ceres and other bodies between Mars and Jupiter which were for some decades considered to be planets. Between then and around 1851, when the number of planets had reached 23, astronomers started using the asteroid for the smaller bodies. With the discovery of Pluto in 1930, most astronomers considered the Solar System to have nine planets and it was roughly one-twentieth the mass of Mercury, which made Pluto by far the smallest planet. Although it was more than ten times as massive as the largest object in the asteroid belt, Ceres. In the 1990s, astronomers began to find objects in the region of space as Pluto. Many of these shared several of Plutos key orbital characteristics, and Pluto started being seen as the largest member of a new class of objects and this led some astronomers to stop referring to Pluto as a planet. Several terms, including subplanet and planetoid, started to be used for the now known as dwarf planets. By 2005, three trans-Neptunian objects comparable in size to Pluto had been reported and it became clear that either they would also have to be classified as planets, or Pluto would have to be reclassified. Astronomers were also confident that more objects as large as Pluto would be discovered, Eris was discovered in January 2005, it was thought to be slightly larger than Pluto, and some reports informally referred to it as the tenth planet. As a consequence, the became a matter of intense debate during the IAU General Assembly in August 2006. The IAUs initial draft proposal included Charon, Eris, and Ceres in the list of planets, dropping Charon from the list, the new proposal also removed Pluto, Ceres, and Eris, because they have not cleared their orbits. The IAUs final Resolution 5A preserved this three-category system for the bodies orbiting the Sun
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Plutoid
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A plutoid or ice dwarf is a trans-Neptunian dwarf planet, i. e. a body orbiting beyond Neptune that is massive enough to be rounded in shape. The term plutoid was adopted by the International Astronomical Union working group Committee on Small Bodies Nomenclature, the term plutoid is not widely used by astronomers, though ice dwarf is not uncommon. There are thought to be thousands of plutoids in the Solar System, the IAU developed this category of astronomical objects as a consequence of its 2006 resolution defining the word planet. Satellites of plutoids are not plutoids themselves, on 24 August 2006, the IAU decided to reclassify Pluto as a dwarf planet, requiring that a planet must clear the neighbourhood around its orbit. The General Assembly of the IAU further resolved, Pluto is recognized as the prototype of a new category of Trans-Neptunian Objects and this new category had been proposed under the name pluton or a plutonian object earlier in the General Assembly. The former was rejected, in part because pluton is a geological term, the definition of the category also fluctuated during its early stages. Ultimately, the final resolution left the definition, like the name. The term was announced after the Executive Committee meeting, along with a simplified definition. However, due to an error, the IAU Working Group for Planetary System Nomenclature was not consulted. As of 2009, the term had not been accepted by the scientific community. Prior to the emergence of the term plutoid as an IAU-sanctioned categorization, the term ice dwarf saw some adoption as a near-synonym to the eventual term plutoid. There are large numbers of objects in the Oort cloud. However, it is not clear whether all so-categorized ice dwarfs are actually icier than icy asteroids such as Ceres, nonetheless, Ceres is sometimes called a terrestrial dwarf to distinguish it from Pluto and Eris. This conception foreshadowed the reclassification of Pluto to dwarf planet and plutoid after the discovery of Eris, with the creation of the term dwarf planet, some ambiguity was created as to which of two IAU bodies would be responsible for naming dwarf planets. Eris had been named through the IAU Committee on Small Body Nomenclature, along with announcing the name plutoid, the IAU decision of 11 June 2008 institutionalized this cooperative process involving the two bodies in the naming of new plutoids. In keeping with minor planet naming guidelines, priority will be given to names proposed by the discovery teams, and plutoids may not share a name with a small Solar System body. When the definition of planet was instated at the IAU General Assembly of 2006, Ceres, Pluto. However, precise regulations as to how hydrostatic equilibrium would be measured were left undefined for the time being, without an official procedure for calculating the lower bound of size to be a dwarf planet, no further bodies could be formally recognized as either dwarf planets or plutoids
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Orbit
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In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet about a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating path around a body, to a close approximation, planets and satellites follow elliptical orbits, with the central mass being orbited at a focal point of the ellipse, as described by Keplers laws of planetary motion. For ease of calculation, in most situations orbital motion is adequately approximated by Newtonian Mechanics, historically, the apparent motions of the planets were described by European and Arabic philosophers using the idea of celestial spheres. This model posited the existence of perfect moving spheres or rings to which the stars and it assumed the heavens were fixed apart from the motion of the spheres, and was developed without any understanding of gravity. After the planets motions were accurately measured, theoretical mechanisms such as deferent. Originally geocentric it was modified by Copernicus to place the sun at the centre to help simplify the model, the model was further challenged during the 16th century, as comets were observed traversing the spheres. The basis for the understanding of orbits was first formulated by Johannes Kepler whose results are summarised in his three laws of planetary motion. Second, he found that the speed of each planet is not constant, as had previously been thought. Third, Kepler found a relationship between the orbital properties of all the planets orbiting the Sun. For the planets, the cubes of their distances from the Sun are proportional to the squares of their orbital periods. Jupiter and Venus, for example, are respectively about 5.2 and 0.723 AU distant from the Sun, their orbital periods respectively about 11.86 and 0.615 years. The proportionality is seen by the fact that the ratio for Jupiter,5. 23/11.862, is equal to that for Venus,0. 7233/0.6152. Idealised orbits meeting these rules are known as Kepler orbits, isaac Newton demonstrated that Keplers laws were derivable from his theory of gravitation and that, in general, the orbits of bodies subject to gravity were conic sections. Newton showed that, for a pair of bodies, the sizes are in inverse proportion to their masses. Where one body is more massive than the other, it is a convenient approximation to take the center of mass as coinciding with the center of the more massive body. Lagrange developed a new approach to Newtonian mechanics emphasizing energy more than force, in a dramatic vindication of classical mechanics, in 1846 le Verrier was able to predict the position of Neptune based on unexplained perturbations in the orbit of Uranus. This led astronomers to recognize that Newtonian mechanics did not provide the highest accuracy in understanding orbits, in relativity theory, orbits follow geodesic trajectories which are usually approximated very well by the Newtonian predictions but the differences are measurable. Essentially all the evidence that can distinguish between the theories agrees with relativity theory to within experimental measurement accuracy
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Semi-major and semi-minor axes
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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 widest points of the perimeter. The semi-major axis is one half of the axis, and thus runs from the centre, through a focus. Essentially, it is the radius of an orbit at the two most distant points. For the special case of a circle, the axis is the radius. One can think of the axis as an ellipses long radius. The semi-major axis of a hyperbola is, depending on the convention, thus it is the distance from the center to either vertex of the hyperbola. A parabola can be obtained as the limit of a sequence of ellipses where one focus is fixed as the other is allowed to move arbitrarily far away in one direction. Thus a and b tend to infinity, a faster than b, the semi-minor axis is a line segment associated with most conic sections that is at right angles with the semi-major axis and has one end at the center of the conic section. It is one of the axes of symmetry for the curve, in an ellipse, the one, in a hyperbola. The semi-major axis is the value of the maximum and minimum distances r max and r min of the ellipse from a focus — that is. In astronomy these extreme points are called apsis, the semi-minor axis of an ellipse is the geometric mean of these distances, b = r max r min. The eccentricity of an ellipse is defined as e =1 − b 2 a 2 so r min = a, r max = a. Now consider the equation in polar coordinates, with one focus at the origin, the mean value of r = ℓ / and r = ℓ /, for θ = π and θ =0 is a = ℓ1 − e 2. In an ellipse, the axis is the geometric mean of the distance from the center to either focus. The semi-minor axis of an ellipse runs from the center of the ellipse to the edge of the ellipse, the semi-minor axis is half of the minor axis. The minor axis is the longest line segment perpendicular to the axis that connects two points on the ellipses edge. The semi-minor axis b is related to the axis a through the eccentricity e. A parabola can be obtained as the limit of a sequence of ellipses where one focus is fixed as the other is allowed to move arbitrarily far away in one direction
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Astronomical unit
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The astronomical unit is a unit of length, roughly the distance from Earth to the Sun. However, that varies as Earth orbits the Sun, from a maximum to a minimum. Originally conceived as the average of Earths aphelion and perihelion, it is now defined as exactly 149597870700 metres, the astronomical unit is used primarily as a convenient yardstick for measuring distances within the Solar System or around other stars. However, it is also a component in the definition of another unit of astronomical length. A variety of symbols and abbreviations have been in use for the astronomical unit. In a 1976 resolution, the International Astronomical Union used the symbol A for the astronomical unit, in 2006, the International Bureau of Weights and Measures recommended ua as the symbol for the unit. In 2012, the IAU, noting that various symbols are presently in use for the astronomical unit, in the 2014 revision of the SI Brochure, the BIPM used the unit symbol au. In ISO 80000-3, the symbol of the unit is ua. Earths orbit around the Sun is an ellipse, the semi-major axis of this ellipse is defined to be half of the straight line segment that joins the aphelion and perihelion. The centre of the sun lies on this line segment. In addition, it mapped out exactly the largest straight-line distance that Earth traverses over the course of a year, knowing Earths shift and a stars shift enabled the stars distance to be calculated. But all measurements are subject to some degree of error or uncertainty, improvements in precision have always been a key to improving astronomical understanding. Improving measurements were continually checked and cross-checked by means of our understanding of the laws of celestial mechanics, the expected positions and distances of objects at an established time are calculated from these laws, and assembled into a collection of data called an ephemeris. NASAs Jet Propulsion Laboratory provides one of several ephemeris computation services, in 1976, in order to establish a yet more precise measure for the astronomical unit, the IAU formally adopted a new definition. Equivalently, by definition, one AU is the radius of an unperturbed circular Newtonian orbit about the sun of a particle having infinitesimal mass. As with all measurements, these rely on measuring the time taken for photons to be reflected from an object. However, for precision the calculations require adjustment for such as the motions of the probe. In addition, the measurement of the time itself must be translated to a scale that accounts for relativistic time dilation
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Charon (moon)
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Charon, also known as Pluto I, is the largest of the five known natural satellites of the dwarf planet Pluto. It was discovered in 1978 at the United States Naval Observatory in Washington, with half the diameter and one eighth the mass of Pluto, it is a very large moon in comparison to its parent body. Its gravitational influence is such that the barycenter of the Pluto–Charon system lies outside Pluto, the New Horizons spacecraft is the only probe that has visited the Pluto system. It approached Charon to within 27,000 km, Charon was discovered by United States Naval Observatory astronomer James Christy, using the 1. 55-meter Flagstaff telescope two months prior. Christy noticed that a slight elongation appeared periodically, later, the bulge was confirmed on plates dating back to April 29,1965. Subsequent observations of Pluto determined that the bulge was due to an accompanying body. The periodicity of the bulge corresponded to Plutos rotation period, which was known from Plutos light curve. This indicated a synchronous orbit, which suggested that the bulge effect was real. Doubts about Charons existence were erased when it and Pluto entered a period of mutual eclipses. This occurs when the Pluto–Charon orbital plane is edge-on as seen from Earth and it was fortuitous that one of these intervals happened to occur soon after Charons discovery. Charon was originally known by the temporary designation S/1978 P1, on June 24,1978, Christy first suggested the name Charon as a scientific-sounding version of his wife Charlenes nickname, Char. The IAU officially adopted the name in late 1985 and it was announced on January 3,1986, there is minor debate over the preferred pronunciation of the name. These indicate only one pronunciation of Charon when referring specifically to Plutos moon, speakers of many languages other than English, and many English-speaking astronomers as well, follow this pronunciation. However, Christy himself pronounced the ch as sh, after his wife Charlene, simulation work published in 2005 by Robin Canup suggested that Charon could have been formed by a collision around 4.5 billion years ago, much like Earth and the Moon. In this model, a large Kuiper belt object struck Pluto at high velocity, destroying itself and blasting off much of Plutos outer mantle, however, such an impact should result in an icier Charon and rockier Pluto than scientists have found. It is now thought that Pluto and Charon might have been two bodies that collided before going into orbit about each other, the collision would have been violent enough to boil off volatile ices like methane but not violent enough to have destroyed either body. The very similar density of Pluto and Charon implies that the parent bodies were not fully differentiated when the impact occurred, Charon and Pluto orbit each other every 6.387 days. The two objects are locked to one another, so each keeps the same face towards the other
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(15760) 1992 QB1
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1992 QB1 was the first trans-Neptunian object to be discovered after Pluto and Charon. It was discovered in 1992 by David C, jewitt and Jane X. Luu at the Mauna Kea Observatory, Hawaii. It is a classical Kuiper belt object and gave rise to the name cubewano for this kind of object, decoding its provisional designation, QB1 reveals that it was the 27th object found in the second half of August of that year. Over 1,500 further objects have been found beyond Neptune, the discoverers suggested the name Smiley for 1992 QB1, but the name was already used for an asteroid 1613 Smiley, named after the American astronomer Charles Hugh Smiley. It has received the number 15760 and remains unnamed, it is referred to simply as QB1. Orbital simulation from JPL at Nasa Ephemeris 1992 QB1 at the JPL Small-Body Database Discovery · Orbit diagram · Orbital elements · Physical parameters
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Makemake
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Makemake is a dwarf planet and perhaps the largest Kuiper belt object in the classical population, with a diameter approximately two thirds that of Pluto. Makemake has one satellite, S/20151. Makemake’s extremely low temperature, about 30 K, means its surface is covered with methane, ethane. Makemake was discovered on March 31,2005, by a led by Michael E. Brown. Initially, it was known as 2005 FY9 and later given the minor-planet number 136472, Makemake was recognized as a dwarf planet by the International Astronomical Union in July 2008. Its name derives from Makemake in the mythology of the Rapa Nui people of Easter Island. Makemake was discovered on March 31,2005, by a team at the Palomar Observatory, led by Michael E. Brown, despite its relative brightness, Makemake was not discovered until well after many much fainter Kuiper belt objects. Most searches for minor planets are conducted relatively close to the ecliptic, besides Pluto, Makemake is the only other dwarf planet that was bright enough that Clyde Tombaugh could have detected it during his search for trans-Neptunian planets around 1930. At the time of Tombaughs survey, Makemake was only a few degrees from the ecliptic, near the border of Taurus and Auriga, at an apparent magnitude of 16.0. This position, however, was very near the Milky Way. Tombaugh continued searching for years after the discovery of Pluto. The provisional designation 2005 FY9 was given to Makemake when the discovery was made public, before that, the discovery team used the codename Easterbunny for the object, because of its discovery shortly after Easter. In July 2008, in accordance with IAU rules for classical Kuiper belt objects,2005 FY9 was given the name of a creator deity. The name of Makemake, the creator of humanity and god of fertility in the myths of the Rapa Nui, as of December 2015, Makemake is 52.4 AU from the Sun, almost as far from the Sun as it ever reaches on its orbit. Makemake follows a very similar to that of Haumea, highly inclined at 29°. Nevertheless, Makemakes orbit is farther from the Sun in terms of both the semi-major axis and perihelion. Its orbital period is nearly 310 years, more than Plutos 248 years, both Makemake and Haumea are currently far from the ecliptic—the angular distance is almost 29°. Makemake is approaching its 2033 aphelion, whereas Haumea passed its aphelion in early 1992, Makemake is a classical Kuiper belt object, which means its orbit lies far enough from Neptune to remain stable over the age of the Solar System
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50000 Quaoar
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50000 Quaoar is a Kuiper belt object roughly half the size of Pluto, with a diameter of 1110±5 km. It is large enough and massive enough that it is probably a dwarf planet and its orbit in the Kuiper belt is not in resonance with Neptune, which means it is a classical Kuiper belt object. Quaoar has one moon, Weywot. Quaoar was discovered in 2002 and its moon in 2007 and it was named after the Tongva creator deity and its moon after his son. Signs of water ice have been found, which suggests that cryovolcanism may be occurring, a small amount of methane is present on Quaoars surface, which can only be retained by the largest Kuiper belt objects. The discovery of this magnitude 18.5 object, at the time located in the constellation Ophiuchus, was announced on October 7,2002, the earliest prediscovery image proved to be a May 25,1954 plate from Palomar Observatory. Quaoar is named for the Tongva creator god, following International Astronomical Union naming conventions for non-resonant Kuiper belt objects, the Tongva are the native people of the area around Los Angeles, where the discovery of Quaoar was made. Brown et al. had picked the name with the more intuitive spelling Kwawar, prior to IAU approval of the name, Quaoar went by the provisional designation 2002 LM60. However, subsequent even-larger discoveries were simply numbered according to the order in which their orbits were confirmed, Quaoar was later supplanted by Eris, Sedna, Haumea, and Makemake, though Sedna was later found to be somewhat smaller than Quaoar. Quaoar is about as massive as Plutos moon Charon, which is approximately 2 1⁄2 times as massive as Orcus, Quaoar is roughly one twelfth the diameter of Earth, one third the diameter of the Moon, and half the size of Pluto. Quaoar was the first trans-Neptunian object to be measured directly from Hubble Space Telescope images, using a new, given its distance Quaoar is on the limit of the HST resolution and its image is consequently smeared on a few adjacent pixels. This method was applied by the same authors to measure the size of Eris. The uncorrected 2004 HST estimates only marginally agree with the 2007 infrared measurements by the Spitzer Space Telescope that suggest a higher albedo and consequently a smaller diameter. Adopting a Uranian-satellite limb darkening profile suggests that the 2004 HST size estimate for Quaoar was approximately 40% too large, using a weighted average of the SST and corrected HST estimates, Quaoar, as of 2010, can be estimated at about 890±70 km in diameter. On 4 May 2011 Quaoar occulted a 16th-magnitude star, which gave 1170 km as the longest chord, New measurement from Herschel Space Observatory with revised data from SST suggested that Quaoar has a diameter of 1070±38 km and its satellite, Weywot, of 81±11 km. Because Quaoar is an object, the mass of the system can be calculated from the orbit of the secondary. Quaoars estimated density of around 2.2 g/cm3 and estimated size of 1,100 km suggests that it is a dwarf planet. Mike Brown estimates that rocky bodies around 900 km in diameter relax into hydrostatic equilibrium, with an estimated mass greater than 1
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20000 Varuna
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20000 Varuna is a large classical Kuiper belt object. It is probably a dwarf planet and it rotates rapidly and hence its shape is probably very elongated. Varuna was discovered on 28 November 2000 by Robert McMillan of Spacewatch and it was given the provisional designation 2000 WR106 and has been precovered in plates dating back to 1954. Varuna is named after a Hindu deity, Varuna was one of the most important deities of the ancient Indians, and he presided over the waters of the heaven and of the ocean and was the guardian of immortality. Due to his association with the waters and the ocean, he is identified with Greek Poseidon. Varuna received the minor planet number 20000 because it was the largest cubewano found so far and was believed to be as large as Ceres, the size of the large Kuiper belt objects can be determined by simultaneous observations of thermal emission and reflected sunlight. In addition, the estimates are model-dependent with the parameters to be assumed. Consequently, the estimates of the albedo vary, resulting in substantial differences in the inferred size. Estimates for the diameter of Varuna have varied from 500 to 1,060 km, multi-band thermal measurements from the Herschel Space Observatory in 2013 yielded a diameter of 668+154 −86 km. A 28-second occultation of an 11.1 magnitude star by Varuna was observed from Camalaú, Paraíba, Brazil, results of the 2010 occultation as seen from São Luís with a duration of 52.5 seconds corresponds with a chord of 1003 km. But Quixadá255 km away had a negative result suggesting a significantly elongated shape is required for Varuna, because the occultation occurred near Varunas maximum brightness, the occultation was observing the maximum apparent surface area for an ellipsoidal shape. Varuna is classified as a classical trans-Neptunian object and follows an orbit with a semi-major axis of ≈43 AU, similar to that of Quaoar. Its orbital period is similar to Quaoar at 283 years, the graph shows the polar view. The spheres illustrate the current positions, relative sizes and colours, the perihelia, aphelia and the dates of passage are also marked. Interestingly, the orbits of Varuna and Pluto have similar inclination and are similarly oriented, at 43 AU and on a near-circular orbit, unlike Pluto, which is in 2,3 orbital resonance with Neptune, Varuna is free from any significant perturbation from Neptune. The ecliptic view illustrates the comparison of Varunas near-circular orbit with that of Pluto, Varuna has a rotational period of approximately 6.34 hours. It has a light curve. Given the rapid rotation, rare for objects so large, Varuna is thought to be an elongated spheroid, since the discovery of Varuna, Haumea, another, even larger, rapidly rotating object, has been discovered and is also thought to have an elongated shape
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19521 Chaos
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19521 Chaos /ˈkeɪ. ɒs/ is a cubewano, a Kuiper-belt object not in resonance with any planet. It is a dwarf planet. Chaos was discovered in 1998 by the Deep Ecliptic Survey with Kitt Peaks 4 m telescope and its albedo is 0. 050+0.030 −0.016, making it, with its absolute magnitude of 4.8, 600+140 −130 km in diameter. It is named after the state of existence in Greek mythology. 19521 Chaos has a period of approximately 309 years. Its orbit is not much more eccentric than the orbit of Pluto,19521 Chaoss orbit is inclined approximately 12° to the ecliptic. Its orbit never crosses the orbit of Neptune, in the online comic Quantum Vibe the lead characters hide on a secret base they have constructed on Chaos to perform experiments undetected
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58534 Logos
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58534 Logos is a small Kuiper-belt object, more specifically a cubewano, notable for having a comparatively large satellite named Zoe. For a small KBO, about 80 km in diameter, it has a high albedo. The system mass is 4.58 ±0. 07×1017 kg, in the Gnostic tradition, Logos and Zoe are a paired emanation of the deity, and part of its creation myth. Logos is a binary with the components of comparable size orbiting the barycentre on an elliptical orbit. Logos companion was discovered on 17 November 2001 from Hubble Space Telescope observations by K. S. Noll, stephens, W. M. Grundy, J. Spencer, R. L. Millis, M. W. Buie, D. Cruikshank, S. C. Tegler, and W. Romanishin and announced on 11 February 2002, after the discovery, it received the provisional designation S/20011. Once confirmed it was officially named Logos I Zoe and it orbits Logos with a semi-major axis of 8217 ±42 km in 309.9 ±0.2 d with an eccentricity of 0.546 ±0.008. Its estimated diameter is 66 km, and mass ×1018 kg, Orbital simulation from JPL / Ephemeris IAUC7824 IAUC795958534 Logos at the JPL Small-Body Database Discovery · Orbit diagram · Orbital elements · Physical parameters
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88611 Teharonhiawako
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88611 Teharonhiawako is a trans-Neptunian object and a member of the Kuiper belt, measuring about 220 km in diameter. It is an object, with a large companion named Sawiskera. Teharonhiawako was discovered on August 20,2001, by the Deep Ecliptic Survey, the primary is named after Teharonhia, wako, a god of maize in the Iroquois creation myth, while the secondary is named after his evil twin brother Sawiskera. The objects were named in 2007, sawiskeras orbit has the following parameters, semi-major-axis—27670 ±120 km, period—828.76 ±0.22 days, eccentricity—0.2494 ±0.0021 and inclination—144.42 ±0. 35°. The total system mass is about 2.4 ×1018 kg, Orbital simulation from JPL / Ephemeris 88611 Teharonhiawako at the JPL Small-Body Database Discovery · Orbit diagram · Orbital elements · Physical parameters
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(33001) 1997 CU29
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1997 CU29, also written as 1997 CU29 is a cubewano. It has a perihelion at 41.660 AU and an aphelion of 45.134 AU.1997 CU29 is about 211 km in diameter and it was discovered on February 6,1997, by David C. Jewitt, Jane X. Luu, Chad Trujillo, and Jun Chen at the Mauna Kea Observatory,1997 CU29 at the JPL Small-Body Database Discovery · Orbit diagram · Orbital elements · Physical parameters
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(55636) 2002 TX300
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2002 TX300 is a bright Kuiper belt object in the outer Solar System estimated to be about 286 kilometres in diameter. It is a member of the Haumea family that was discovered on October 15,2002 by the Near-Earth Asteroid Tracking program. 2002 TX300 is a classical Kuiper belt object with a magnitude between that of 50000 Quaoar and 20000 Varuna. 2002 TX300 has the most eccentric and inclined orbit of the three, a variability of the visual brightness was also detected which could fit to 7.9 h or 15.8 h rotational period. The changes in brightness are quite close to the error margin, the diagrams to the left show polar and ecliptic views of the orbits of the two cubewanos. The perihelia and the aphelia are marked with the dates of passage, the present positions are marked with the spheres, illustrating relative sizes and differences in albedo. 2002 TX300 is classified as a classical Kuiper belt object and follows a very similar to that of Haumea, highly inclined and moderately eccentric. Other mid-sized cubewanos follow similar orbits as well, notably 2002 UX25 and 2002 AW197 and it has been observed 303 times, with precovery images back to 1954. In 2004, the non-detection of IR thermal emissions put a limit of 709 kilometres on its diameter. In a 2006 International Astronomical Union press release discussing the IAU2006 draft proposal, in 2007, measurements by the Spitzer Space Telescope showed that it may be less than 641 kilometres in diameter. In 2008, it was considered to be a planet based on the its lightcurve amplitude. Because 2002 TX300 is a member of the Haumea family, it is assumed to have an albedo of around 0.7,2002 TX300 occulted a relatively bright apparent magnitude 13.1 star in the constellation of Andromeda on October 9,2009. This event was visible from Australia, possibly New Zealand, the RA and declination for this event was about 003713.64 +282223.2. Detailed information for observers was made available, the occultation produced a diameter of 286 kilometres, suggesting an albedo of about 0.88. Somewhere between a size of 200 kilometres and 400 kilometres, an icy body becomes rounded by its own gravity, with the exception of Neptunes moon Proteus, and possibly Eriss moon Dysnomia, all icy moons with diameters 400 km or more are known to be spherical. Mike Brown lists it as a dwarf planet. The spectrum in the visible and near-infrared rages is very similar to that of Charon, mineralogical analysis indicates a substantial fraction of large ice particles. The signal-to-noise ratio of the observations was insufficient to differentiate between amorphous or crystalline ice, the proportion of highly processed organic materials, typically present on numerous trans-Neptunian objects, is very low
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(55565) 2002 AW197
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2002 AW197 is a classical Kuiper belt object. Measurements with the Spitzer Space Telescope have confirmed 2002 AW197 as a dwarf planet. Light-curve-amplitude analysis shows only small deviations, which suggests that 2002 AW197 is a spheroid with small albedo spots, tancredi accepts it as a dwarf planet. Mike Browns website lists it as a likely dwarf planet. It was discovered on January 10,2002, by Michael Brown et al and it is located near the Kuiper cliff. Observations of thermal emissions by the Spitzer Space Telescope in 2007 give a diameter of 734+116 −108 km, the newest estimate is 768+39 −38 km ESO analysis of spectra reveals a strong red slope and no presence of water ice suggesting organic material. As of 2013, it is currently 46.0 AU from the Sun and it will come to perihelion around 2078. High Albedo KBO2002 AW197, The Astronomical Journal Letters,624,53, abstract Doressoundiram, A. Barucci, M. A. Tozzi, G. P. Poulet, F. Boehnhardt, H. de Bergh, C. Spectral characteristics and modeling of the trans-neptunian object 2002 AW197 and the Centaurs 2002 GB10 and 2002 GO9, ESO Large Program on TNOs, planetary and Space Science,53, Issue 14-15, p. 1501–1509. Abstract AstDys orbital elements Orbital simulation from JPL / Horizons Ephemeris 2002 AW197 at the JPL Small-Body Database Discovery · Orbit diagram · Orbital elements · Physical parameters
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(55637) 2002 UX25
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2002 UX25 is a possible dwarf planet that orbits the Sun in the Kuiper belt beyond Neptune. Its orbit takes roughly 280 years, and it has one known moon and this moon makes it much easier to calculate mass, and when the size is known, also a density. The low density of about 0.82 g/cm3 surprised astronomers and it is a trans-Neptunian object with an absolute magnitude of 4.0, making it highly likely to be a dwarf planet. The Spitzer Space Telescope results estimate it to be about 681 km in diameter and it was discovered on 30 October 2002, by the Spacewatch program. It is a mid-sized cubewano similar in size to 20000 Varuna,2002 UX25 has a perihelion of 36.7 AU, which it will next reach in 2065. As of 2010,2002 UX25 is 41 AU from the Sun, the Minor Planet Center classifies 2002 UX25 as a cubewano while the Deep Ecliptic Survey classifies it as scattered-extended. The DES using a 10 My integration shows it with a perihelion distance of 36.3 AU.2002 UX25 has been observed 60 times with precovery images back to 1991. 2002 UX25 has an diameter of 665±29 km, and most icy objects around 400 km in diameter are thought to be spherical. Michael Browns website lists it as likely a dwarf planet. However, light-curve analysis has questioned whether it is actually a dwarf planet, a variability of the visual brightness was detected which could be fit to a period of 14.38 or 16.78 h. The light-curve amplitude is ΔM =0. 21±0.06, assuming equal albedos for the primary and secondary it leads to the size estimates of ~664 km and ~190 km, respectively. If the albedo of the secondary is half of that of the primary the estimates become ~640 and ~260 km, respectively. 2002 UX25 has red featureless spectrum in the visible and near-infrared but has a slope in the K-band. It is redder than Varuna, unlike its neutral-colored twin 2002 TX300, in spite of similar brightness and orbital elements. With a density of 0.82 g/cm3, assuming that the primary, why this should be is not well understood, because objects of its size in the Kuiper belt often contain a fair amount of rock and are hence pretty dense. To have a composition to others large KBOs, it would have to be exceptionally porous. The discovery of a satellite of 2002 UX25 was reported in IAUC8812 on 22 February 2007, the satellite was detected using the Hubble Space Telescope in August 2005. The satellite was found at 0.16 arcsec from the primary with an apparent magnitude difference of 2.5 and it orbits the primary in 8. 309±0.0002 days, at a distance of 4770±40 km, yielding a system mass of ×1020 kg
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Haumea
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Haumea, minor-planet designation 136108 Haumea, is a dwarf planet located beyond Neptunes orbit. On September 17,2008, it was recognized as a planet by the International Astronomical Union and named after Haumea. Haumeas mass is about one-third that of Pluto, and 1/1400 that of Earth, although its shape has not been directly observed, calculations from its light curve indicate that it is a triaxial ellipsoid, with its major axis twice as long as its minor. Its gravity is thought to be sufficient for it to have relaxed into hydrostatic equilibrium, two teams claim credit for the discovery of Haumea. Mike Brown and his team at Caltech discovered Haumea in December 2004 on images they had taken on May 6,2004, on July 20,2005, they published an online abstract of a report intended to announce the discovery at a conference in September 2005. At around this time, José Luis Ortiz Moreno and his team at the Instituto de Astrofísica de Andalucía at Sierra Nevada Observatory in Spain found Haumea on images taken on March 7–10,2003. Ortiz emailed the Minor Planet Center with their discovery on the night of July 27,2005, Ortiz later admitted he had accessed the Caltech observation logs but denied any wrongdoing, stating he was merely verifying whether they had discovered a new object. However, the IAU announcement on September 17,2008, that Haumea had been accepted as a dwarf planet, did not mention a discoverer. Until it was given a permanent name, the Caltech discovery team used the nickname Santa among themselves, because they had discovered Haumea on December 28,2004, the Spanish team were the first to file a claim for discovery to the Minor Planet Center, in July 2005. On July 29,2005, Haumea was given the provisional designation 2003 EL61, on September 7,2006, it was numbered and admitted into the official minor planet catalogue as 2003 EL61. The names were proposed by David Rabinowitz of the Caltech team, Haumea is the matron goddess of the island of Hawaiʻi, where the Mauna Kea Observatory is located. The two known moons, also believed to have formed in this manner, are named after two of Haumeas daughters, Hiʻiaka and Nāmaka. The proposal by the Ortiz team, Ataecina, did not meet IAU naming requirements, Haumea is a plutoid, a dwarf planet beyond Neptunes orbit. Haumea appears to have an ellipsoid shape resulting its rapid rotation complicated by tidal interactions with its moons. This contrasts with the simpler oblate shape typically assumed by less rapidly rotating astronomical bodies such as the Earth, in other words, Haumea is spinning so fast that if it spun much faster these bulges would distort into a dumbbell shape and split the planet in two. Haumea was initially listed as a classical Kuiper belt object in 2006 by the Minor Planet Center, the nominal trajectory suggests that it is in the weak 7,12 resonance with Neptune, because its perihelion distance of 35 AU is near the limit of stability with Neptune. There are precovery images of Haumea dating back to March 22,1955 from the Palomar Mountain Digitized Sky Survey, further observations of the orbit will be required to verify its dynamic status. Haumea has a period of 284 Earth years, a perihelion of 35 AU
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Orbital eccentricity
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The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is an orbit, values between 0 and 1 form an elliptical orbit,1 is a parabolic escape orbit. The term derives its name from the parameters of conic sections and it is normally used for the isolated two-body problem, but extensions exist for objects following a rosette orbit through the galaxy. In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit, the eccentricity of this Kepler orbit is a non-negative number that defines its shape. The limit case between an ellipse and a hyperbola, when e equals 1, is parabola, radial trajectories are classified as elliptic, parabolic, or hyperbolic based on the energy of the orbit, not the eccentricity. Radial orbits have zero angular momentum and hence eccentricity equal to one, keeping the energy constant and reducing the angular momentum, elliptic, parabolic, and hyperbolic orbits each tend to the corresponding type of radial trajectory while e tends to 1. For a repulsive force only the trajectory, including the radial version, is applicable. For elliptical orbits, a simple proof shows that arcsin yields the projection angle of a circle to an ellipse of eccentricity e. For example, to view the eccentricity of the planet Mercury, next, tilt any circular object by that angle and the apparent ellipse projected to your eye will be of that same eccentricity. From Medieval Latin eccentricus, derived from Greek ἔκκεντρος ekkentros out of the center, from ἐκ- ek-, eccentric first appeared in English in 1551, with the definition a circle in which the earth, sun. Five years later, in 1556, a form of the word was added. The eccentricity of an orbit can be calculated from the state vectors as the magnitude of the eccentricity vector, e = | e | where. For elliptical orbits it can also be calculated from the periapsis and apoapsis since rp = a and ra = a, where a is the semimajor axis. E = r a − r p r a + r p =1 −2 r a r p +1 where, rp is the radius at periapsis. For Earths annual orbit path, ra/rp ratio = longest_radius / shortest_radius ≈1.034 relative to center point of path, the eccentricity of the Earths orbit is currently about 0.0167, the Earths orbit is nearly circular. Venus and Neptune have even lower eccentricity, over hundreds of thousands of years, the eccentricity of the Earths orbit varies from nearly 0.0034 to almost 0.058 as a result of gravitational attractions among the planets. The table lists the values for all planets and dwarf planets, Mercury has the greatest orbital eccentricity of any planet in the Solar System. Such eccentricity is sufficient for Mercury to receive twice as much solar irradiation at perihelion compared to aphelion, before its demotion from planet status in 2006, Pluto was considered to be the planet with the most eccentric orbit
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Perihelion and aphelion
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The perihelion is the point in the orbit of a celestial body where it is nearest to its orbital focus, generally a star. It is the opposite of aphelion, which is the point in the orbit where the body is farthest from its focus. The word perihelion stems from the Ancient Greek words peri, meaning around or surrounding, aphelion derives from the preposition apo, meaning away, off, apart. According to Keplers first law of motion, all planets, comets. Hence, a body has a closest and a farthest point from its parent object, that is, a perihelion. Each extreme is known as an apsis, orbital eccentricity measures the flatness of the orbit. Because of the distance at aphelion, only 93. 55% of the solar radiation from the Sun falls on a given area of land as does at perihelion. However, this fluctuation does not account for the seasons, as it is summer in the northern hemisphere when it is winter in the southern hemisphere and vice versa. Instead, seasons result from the tilt of Earths axis, which is 23.4 degrees away from perpendicular to the plane of Earths orbit around the sun. Winter falls on the hemisphere where sunlight strikes least directly, and summer falls where sunlight strikes most directly, in the northern hemisphere, summer occurs at the same time as aphelion. Despite this, there are larger land masses in the northern hemisphere, consequently, summers are 2.3 °C warmer in the northern hemisphere than in the southern hemisphere under similar conditions. Apsis Ellipse Solstice Dates and times of Earths perihelion and aphelion, 2000–2025 from the United States Naval Observatory
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Orbital inclination
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Orbital inclination measures the tilt of an objects orbit around a celestial body. It is expressed as the angle between a plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth directly above the equator, the plane of the orbit is the same as the Earths equatorial plane. The general case is that the orbit is tilted, it spends half an orbit over the northern hemisphere. If the orbit swung between 20° north latitude and 20° south latitude, then its orbital inclination would be 20°, the inclination is one of the six orbital elements describing the shape and orientation of a celestial orbit. It is the angle between the plane and the plane of reference, normally stated in degrees. For a satellite orbiting a planet, the plane of reference is usually the plane containing the planets equator, for planets in the Solar System, the plane of reference is usually the ecliptic, the plane in which the Earth orbits the Sun. This reference plane is most practical for Earth-based observers, therefore, Earths inclination is, by definition, zero. Inclination could instead be measured with respect to another plane, such as the Suns equator or the invariable plane, the inclination of orbits of natural or artificial satellites is measured relative to the equatorial plane of the body they orbit, if they orbit sufficiently closely. The equatorial plane is the perpendicular to the axis of rotation of the central body. An inclination of 30° could also be described using an angle of 150°, the convention is that the normal orbit is prograde, an orbit in the same direction as the planet rotates. Inclinations greater than 90° describe retrograde orbits, thus, An inclination of 0° means the orbiting body has a prograde orbit in the planets equatorial plane. An inclination greater than 0° and less than 90° also describe prograde orbits, an inclination of 63. 4° is often called a critical inclination, when describing artificial satellites orbiting the Earth, because they have zero apogee drift. An inclination of exactly 90° is an orbit, in which the spacecraft passes over the north and south poles of the planet. An inclination greater than 90° and less than 180° is a retrograde orbit, an inclination of exactly 180° is a retrograde equatorial orbit. For gas giants, the orbits of moons tend to be aligned with the giant planets equator, the inclination of exoplanets or members of multiple stars is the angle of the plane of the orbit relative to the plane perpendicular to the line-of-sight from Earth to the object. An inclination of 0° is an orbit, meaning the plane of its orbit is parallel to the sky. An inclination of 90° is an orbit, meaning the plane of its orbit is perpendicular to the sky
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Orbital resonance
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Orbital resonances greatly enhance the mutual gravitational influence of the bodies, i. e. their ability to alter or constrain each others orbits. In most cases, this results in an interaction, in which the bodies exchange momentum. Under some circumstances, a resonant system can be stable and self-correcting, examples are the 1,2,4 resonance of Jupiters moons Ganymede, Europa and Io, and the 2,3 resonance between Pluto and Neptune. Unstable resonances with Saturns inner moons give rise to gaps in the rings of Saturn, thus the 2,3 ratio above means Pluto completes two orbits in the time it takes Neptune to complete three. In the case of resonance relationships between three or more bodies, either type of ratio may be used and the type of ratio will be specified. Since the discovery of Newtons law of gravitation in the 17th century. The stable orbits that arise in a two-body approximation ignore the influence of other bodies and it was Laplace who found the first answers explaining the remarkable dance of the Galilean moons. It is fair to say that this field of study has remained very active since then. Before Newton, there was consideration of ratios and proportions in orbital motions, in what was called the music of the spheres. In general, a resonance may involve one or any combination of the orbit parameters. Act on any scale from short term, commensurable with the orbit periods, to secular. Lead to either long-term stabilization of the orbits or be the cause of their destabilization, a mean-motion orbital resonance occurs when two bodies have periods of revolution that are a simple integer ratio of each other. Depending on the details, this can either stabilize or destabilize the orbit, stabilization may occur when the two bodies move in such a synchronised fashion that they never closely approach. For instance, The orbits of Pluto and the plutinos are stable, despite crossing that of the much larger Neptune, the resonance ensures that, when they approach perihelion and Neptunes orbit, Neptune is consistently distant. Other Neptune-crossing bodies that were not in resonance were ejected from that region by strong perturbations due to Neptune. There are also smaller but significant groups of resonant trans-Neptunian objects occupying the 1,1,3,5,4,7,1,2 and 2,5 resonances, among others, with respect to Neptune. In the asteroid belt beyond 3.5 AU from the Sun, orbital resonances can also destabilize one of the orbits. For small bodies, destabilization is actually far more likely, for instance, In the asteroid belt within 3.5 AU from the Sun, the major mean-motion resonances with Jupiter are locations of gaps in the asteroid distribution, the Kirkwood gaps
35.
Ecliptic
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The ecliptic is the apparent path of the Sun on the celestial sphere, and is the basis for the ecliptic coordinate system. It also refers to the plane of this path, which is coplanar with the orbit of Earth around the Sun, the motions as described above are simplifications. Due to the movement of Earth around the Earth–Moon center of mass, due to further perturbations by the other planets of the Solar System, the Earth–Moon barycenter wobbles slightly around a mean position in a complex fashion. The ecliptic is actually the apparent path of the Sun throughout the course of a year, because Earth takes one year to orbit the Sun, the apparent position of the Sun also takes the same length of time to make a complete circuit of the ecliptic. With slightly more than 365 days in one year, the Sun moves a little less than 1° eastward every day, again, this is a simplification, based on a hypothetical Earth that orbits at uniform speed around the Sun. The actual speed with which Earth orbits the Sun varies slightly during the year, for example, the Sun is north of the celestial equator for about 185 days of each year, and south of it for about 180 days. The variation of orbital speed accounts for part of the equation of time, if the equator is projected outward to the celestial sphere, forming the celestial equator, it crosses the ecliptic at two points known as the equinoxes. The Sun, in its apparent motion along the ecliptic, crosses the equator at these points, one from south to north. The crossing from south to north is known as the equinox, also known as the first point of Aries. The crossing from north to south is the equinox or descending node. Likewise, the ecliptic itself is not fixed, the gravitational perturbations of the other bodies of the Solar System cause a much smaller motion of the plane of Earths orbit, and hence of the ecliptic, known as planetary precession. The combined action of two motions is called general precession, and changes the position of the equinoxes by about 50 arc seconds per year. Once again, this is a simplification, periodic motions of the Moon and apparent periodic motions of the Sun cause short-term small-amplitude periodic oscillations of Earths axis, and hence the celestial equator, known as nutation. Obliquity of the ecliptic is the used by astronomers for the inclination of Earths equator with respect to the ecliptic. It is about 23. 4° and is currently decreasing 0.013 degrees per hundred years due to planetary perturbations, the angular value of the obliquity is found by observation of the motions of Earth and other planets over many years. From 1984, the Jet Propulsion Laboratorys DE series of computer-generated ephemerides took over as the ephemeris of the Astronomical Almanac. Obliquity based on DE200, which analyzed observations from 1911 to 1979, was calculated, jPLs fundamental ephemerides have been continually updated. J. Laskar computed an expression to order T10 good to 0″. 04/1000 years over 10,000 years, all of these expressions are for the mean obliquity, that is, without the nutation of the equator included
36.
Degree (angle)
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A degree, usually denoted by °, is a measurement of a plane angle, defined so that a full rotation is 360 degrees. It is not an SI unit, as the SI unit of measure is the radian. Because a full rotation equals 2π radians, one degree is equivalent to π/180 radians, the original motivation for choosing the degree as a unit of rotations and angles is unknown. One theory states that it is related to the fact that 360 is approximately the number of days in a year. Ancient astronomers noticed that the sun, which follows through the path over the course of the year. Some ancient calendars, such as the Persian calendar, used 360 days for a year, the use of a calendar with 360 days may be related to the use of sexagesimal numbers. The earliest trigonometry, used by the Babylonian astronomers and their Greek successors, was based on chords of a circle, a chord of length equal to the radius made a natural base quantity. One sixtieth of this, using their standard sexagesimal divisions, was a degree, Aristarchus of Samos and Hipparchus seem to have been among the first Greek scientists to exploit Babylonian astronomical knowledge and techniques systematically. Timocharis, Aristarchus, Aristillus, Archimedes, and Hipparchus were the first Greeks known to divide the circle in 360 degrees of 60 arc minutes, eratosthenes used a simpler sexagesimal system dividing a circle into 60 parts. Furthermore, it is divisible by every number from 1 to 10 except 7 and this property has many useful applications, such as dividing the world into 24 time zones, each of which is nominally 15° of longitude, to correlate with the established 24-hour day convention. Finally, it may be the case more than one of these factors has come into play. For many practical purposes, a degree is a small enough angle that whole degrees provide sufficient precision. When this is not the case, as in astronomy or for geographic coordinates, degree measurements may be written using decimal degrees, with the symbol behind the decimals. Alternatively, the sexagesimal unit subdivisions can be used. One degree is divided into 60 minutes, and one minute into 60 seconds, use of degrees-minutes-seconds is also called DMS notation. These subdivisions, also called the arcminute and arcsecond, are represented by a single and double prime. For example,40. 1875° = 40° 11′ 15″, or, using quotation mark characters, additional precision can be provided using decimals for the arcseconds component. The older system of thirds, fourths, etc. which continues the sexagesimal unit subdivision, was used by al-Kashi and other ancient astronomers, but is rarely used today
37.
Binary asteroid
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A binary asteroid is a system of two asteroids orbiting their common barycenter. The binary nature of 243 Ida was discovered when the Galileo spacecraft flew by the asteroid in 1993, since then numerous binary asteroids and several triple asteroids have been detected. The mass ratio of the two components of a system is an important characteristic. Most binary asteroids have a mass ratio, i. e. a relatively small satellite in orbit around the main component. Systems with a satellite, or moon, include 22 Kalliope,45 Eugenia,87 Sylvia,107 Camilla,121 Hermione,130 Elektra,243 Ida,283 Emma. Some binary systems have a ratio near unity, i. e. two components of similar mass. They include 90 Antiope and Hermes, several theories have been posited to explain the formation of binary-asteroid systems. The satellites orbiting large main-belt asteroids such as 22 Kalliope,45 Eugenia or 87 Sylvia may have formed by disruption of a parent body after impact or fission after an oblique impact. Trans-Neptunian binaries may have formed during the formation of the Solar System by mutual capture or three-body interaction, near-Earth asteroids, which orbit in the inner part of the Solar System, most likely form by spin-up and mass shedding, likely as a result of the YORP effect. Numerical simulations confirm that when solar energy spins a “rubble pile” asteroid to a sufficiently fast rate by the YORP effect and this process also exposes fresh material at the poles of the asteroid. 2001 SN263 and 1994 CC Minor-planet moon Yarkovsky–OKeefe–Radzievskii–Paddack effect
38.
Perturbation (astronomy)
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In astronomy, perturbation is the complex motion of a massive body subject to forces other than the gravitational attraction of a single other massive body. The other forces can include a body, resistance, as from an atmosphere. The study of perturbations began with the first attempts to predict planetary motions in the sky, in ancient times the causes were a mystery. Newton, at the time he formulated his laws of motion and of gravitation, applied them to the first analysis of perturbations, the complex motions of gravitational perturbations can be broken down. The hypothetical motion that the body follows under the effect of one other body only is typically a conic section. This is called a problem, or an unperturbed Keplerian orbit. The differences between that and the motion of the body are perturbations due to the additional gravitational effects of the remaining body or bodies. If there is one other significant body then the perturbed motion is a three-body problem. A general analytical solution exists for the problem, when more than two bodies are considered analytic solutions exist only for special cases. Even the two-body problem becomes insoluble if one of the bodies is irregular in shape, most systems that involve multiple gravitational attractions present one primary body which is dominant in its effects. The gravitational effects of the bodies can be treated as perturbations of the hypothetical unperturbed motion of the planet or satellite around its primary body. In methods of general perturbations, general differential equations, either of motion or of change in the elements, are solved analytically, usually by series expansions. The result is expressed in terms of algebraic and trigonometric functions of the orbital elements of the body in question. This can be applied generally to many different sets of conditions, historically, general perturbations were investigated first. The classical methods are known as variation of the elements, variation of parameters or variation of the constants of integration, in these methods, it is considered that the body is always moving in a conic section, however the conic section is constantly changing due to the perturbations. General perturbations is applicable if the perturbing forces are about one order of magnitude smaller, or less. In the Solar System, this is usually the case, Jupiter, general perturbation methods are preferred for some types of problems, as the source of certain observed motions are readily found. In effect, the positions and velocities are perturbed directly, special perturbations can be applied to any problem in celestial mechanics, as it is not limited to cases where the perturbing forces are small
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(119951) 2002 KX14
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2002 KX14, also written as 2002 KX14, is a trans-Neptunian object residing within the Kuiper belt. It was discovered on 17 May 2002 by Michael E. Brown and it has a semi-major axis, orbital period and orbital eccentricity close to that of a plutino. The orbital periods of plutinos cluster around 247.2 years, however,2002 KX14 is not a plutino, because is not in resonance with Neptune, and it may have formed near its present nearly circular orbit lying almost perfectly on the ecliptic. It may have remained dynamically cold and thus its orbit may not be a result of significant perturbations during Neptunes outward planetary migration. The Deep Ecliptic Survey currently shows it as a cubewano based on a 10-million-year integration of the orbit and it comes to opposition in late May at an apparent magnitude of 20.4. This makes it about 360 times fainter than Pluto
40.
Brett J. Gladman
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He holds the Canada Research Chair in Planetary Astronomy. Gladman is best known for his work in astronomy in the Solar System. He also studies planet formation, especially the puzzle of how the giant planets came to be, Gladman was awarded the H. C. Urey Prize by the Division of Planetary Sciences of the American Astronomical Society in 2002, the main-belt asteroid 7638 Gladman is named in his honor. In 2008-2011 he served as member and chair of the Science Advisory Council of the Canada-France-Hawaii Telescope on Mauna Kea in Hawaii and he was awarded a Killam research fellowship in 2015. List of minor planet discoverers Brett Gladman at the Astronomy group of the Dept. of Physics and Astronomy, UBC and Institute of Planetary Science
. Bibcode:2002AJ....124.2279D. doi:10.1086/342447.
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