Eris (Asteroid No.: 136199 Eris) is the second largest dwarf planet in the known solar system, ranking the ninth in mass among all the celestial bodies that directly orbit the sun.Its estimated diameter is about 2326 ± 12 km.[1]
In 2010, Mars starsOccultationIts diameter is 2326 ± 12 kilometers (1445 ± 7 miles),[2]Slightly smaller than Pluto.[3-4]In July 2015, Pluto was measured as 2377 ± 4 kilometers (1477 ± 2 miles) by New Horizons.[5-6]The mass of Eris is 0.27% of that of the earthPluto127% of mass.[7-8]
Yishen Star isOuter Sea Uranus(TNO), also high eccentricityDiscrete discCelestial objects (SDO), with a larger satelliteDysnomia (Dysnomia), in February 2016, its distance from the sun was 96.3 astronomical units (14.41 billion kilometers),[9]About three times the size of Pluto.Except someLong-period cometUntil December 17, 20182018 VG18After Faroute, Eris and Eris are the most remote natural objects known in the solar system.[9]
Chinese name
Eris
Foreign name
Eris
Alias
Xena、(136199) Eris、2003 UBthree hundred and thirteen[10]
Eris was founded by the California Institute of TechnologyMichael E. Brown(Mike E. Brown)Chad Trujillo (Chad Trujillo) and Yale UniversityDavid Rabinowitz (David Rabinowitz),[11]It was found in the image taken on January 5, 2005 and October 21, 2003.[15]The discovery of Eris was announced by them on July 29, 2005, and the discovery was also announced on the same dayBird God Star(Makemake) Two days ago, they also announced that they had foundHaumea （Haumea），[16]Part of the reason is the controversy about the discoverer of Pregnancy God Star.The search team has been systematically searching for large objects outside the solar system for many years, and has led the discovery of several other large offshore Uranian objects, includingGenesis Star（50000 Quaoar），Orcus (90482 Orcus) andsedna （90377 Sedna）。[17]
On October 21, 2003, the team usedPalomar Observatory 1.2 by Michael Oschin·Schmidt telescopeRoutine observation was carried out, but because of the very slow movement of Mars in the sky at that time, no image of Mars was found.The reason is that the automatic image search software excludes all movement speeds below 1.5 per hourAngular secondTo reduce the number of false positive false positives returned.[15]When Sedna was discovered in 2003Angular secondInspired by this, the research team of the team used a lower angle movement limit to analyze the previous data again and conduct manual troubleshooting with the naked eye.In January 2005, a new analysis found the Eris star moving slowly under the background sky.[15]
Subsequent observations can preliminarily determine the orbit of Mars, so that the distance of celestial bodies can be estimated.[15]The team originally planned to postpone the publication of the discovery of the bright celestial bodies Eris and Ornithology until subsequent observations could more accurately determine its size and mass.But on July 27, another team from Spain askedAsteroid centerThe discovery of Triton was announced, which caused great pressure on the discovery controversy. The team had to announce the discovery of Triton and Oryx in advance on July 29.[11]
The image of Eris can be traced back to September 3, 1954.[10]In October 2005, more in-depth observation found that Eris had a satellite, which was later namedDysnomia （Dysnomia）。Through the observation of the orbit of Iris I, scientists can determine the mass of Iris. In June 2007, they calculated the mass of Iris as (1.66 ± 0.02) × 10twenty-twoKg,[7]27% ± 2% heavier than Pluto.
The arrow points to the motion track of Eris in the picture when it is found
Surface temperature minimum average maximum (approximate) 30 K42.5 K55 K
Spectrum type
B-V=0.78, V-R=0.45
Apparent magnitude
eighteen point seven
Absolute magnitude (H)
−1.19 ± 0.3
Angular diameter
40 milliarcsec[20]
Physical characteristics
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Eris is a dwarf planet outside Neptune's orbit（Plutonian Object ）。[22]Its orbital characteristics can be more specifically classified asDiscrete discThe celestial body (SDO), or the gravitational interaction with Neptune during the formation of the solar systemKuiper belt"Scattering" to distant and rarer orbits of the Outer Sea Uranus objects.Although its high orbital inclination is rare among the known discrete disk objects, the theoretical model shows that the objects initially located near the inner edge of the Kuiper Belt will disperse into the orbit with a higher inclination than the outer edge objects.[23]
Because Eris was initially thought to be larger than Pluto, NASA and the media described Eris as the "tenth planet" when they found it.[24]In order to deal with the uncertainty of its status and the continuous debate on whether Pluto should be classified as a planet, the International Astronomical Union has appointed a group of astronomers toplanetThe term is defined precisely enough to determine this issue.On August 24, 2006, the International Astronomical Union adopted the "Definition of Planets in the Solar System". Both Eris and Pluto are classified as dwarf planets, which are different from the newly defined planets.[25]Since then, Brown has expressed support for this classification.[26]Subsequently, the International Astronomical Union added Eris to the minor star list and numbered it (136199) Eris.[27]
Schematic diagram of Outer Sea Uranus, where Eris is a discrete disk object
Track characteristics
The orbital period of Eris is 559 years.[2]Its maximum distance from the sun（Apohelion）Probably 97.65AU, the closest distance to the sun（Perihelion）37.91AU.[2]It was in 1698[28]By 1699[29]Reached perihelion in 1977[29]Reaching aphelion, and in 2256[29]To 2258[30]Return to perihelion between.The orbits of the eight planets are roughly in the same plane as the Earth. In contrast, the orbit of Eris is tilted, relative toEclipticThe inclination of is about 44 degrees.[10]When found, exceptLong-period cometandSpace probeIn addition, Eris and its satellites are the most distant known celestial bodies in the solar system.[11][31]Until 20182018 VG18Until then, the record it held was broken.[32]
Schematic diagram of geostationary orbit with high inclination and high eccentricity
In 800 years, Eris will be closer to the sun than Pluto
The orbital eccentricity of Eris is very high, making Eris reach within 37.9AU of the sun, which is the typical perihelion of the scattered object.[34]This distance is within Pluto's orbit, but it can still avoid direct interaction with Neptune (about 37 AU).[35]On the other hand, Pluto, like other Pluto like objects, can cross the orbit of Neptune along the orbit with small inclination and eccentricity and under the protection of orbital resonance.[36]In about 800 years, Eris will be closer to the sun than Pluto.
In 2007, the apparent magnitude of Eris was 18.7, which was bright enough to be observed by some amateur telescopes.[37]The 200mm (7.9-inch) telescope equipped with CCD can detect Eris under favorable conditions.The reason why Eris was not discovered until recently is its steep orbital inclination. In the past, the search for large objects in the periphery of the solar system often focused on the ecliptic plane, where most of them were found.
Because of its highly tilted orbit, Eris only passes through a few of the traditional zodiac constellations.Most recently in the constellation Cetus.From 1876 to 1929, it was in Yufu, and from 1840 to 1875, it was in Phoenix.By 2036 it will enter Pisces (the zodiac), stay there until 2065, and then enter Aries (the zodiac).[29]Then it will move to the northern sky, enter Perseus in 2128, and enter Leopard in 2173 (declination will reach the northernmost).
The motion track of Eris on the celestial sphere is very slow
In November 2010, Eris became the most distant star from EarthOccultationone of.[13]The preliminary data of the event cast doubt on the previous scale estimate.[13]The discovery team announced the final result of occultation, and the diameter of Eris is estimated to be 2326 ± 12km.[2]
In November 2010, the schematic diagram of multiple observatories' observation of Erin's star cover
This result makes Eris slightly smaller in area and diameter than Pluto, whose diameter and diameter are 2372 ± 4km, although Eris has a larger mass.This also brings the albedo of Eris to 0.96, which is higher than that of any other large object except Enceladus in the solar systemAlbedo。[2]It is speculated that the high albedo is due to the fact that the Eris' eccentric orbit keeps it away from the sun, and the temperature fluctuations lead to the continuous replenishment of surface ice.[38]
The mass of Mars can be calculated more accurately.15.774 days recognized by Dysnomia[7][39]Rotation periodIt is calculated that Eris is 27% larger than Pluto.According to the occultation results in 2011, the density of Eris is 2.52 ± 0.07g/cmthree, which is much higher than Pluto, so Eris can only be mainly composed of rock material.[2]adoptRadioactive decayThe model of internal heating indicates that there may be an internal ocean of liquid water at the mantle core boundary of Eris.[40]
In July 2015, nearly ten years after Eris was regarded as the ninth known celestial body orbiting the sun directly,New Horizon No(New Horizons) mission's close range imaging more accurately determined that Pluto's volume is slightly larger than Eris, rather than slightly smaller than Eris as previously thought.[41]At present, Eris is the tenth largest known celestial body orbiting the sun directly, but it is still the ninth largest by mass.
Surface and atmosphere
On January 25, 2005, through the spectral observation of Eris with the 8-meter Gemini North Telescope located in Hawaii, the discovery team made a preliminary identification.The infrared light reflected from the object shows the existence of methane ice, indicating that the surface may be similar to Pluto. Among the known Neptune objects at that time, only Pluto has methane on the surface, and Triton also has methane on the surface.[42]
Due to the remote and eccentric orbit of Eris, its surface temperature is estimated to vary from 30 to 56K (− 243.2 to − 217.2 ° C).[11]
With the reddish Pluto andTriton Different, Eris looks almost white.[11]Pluto's reddish color is due to the presence ofTorin(tholins) deposits. When these deposits darken the surface, lower albedo will lead to higher temperature, which will cause evaporation of methane deposits.On the contrary, Eris is far enough from the sun, and even in places with low albedo, methane cancoagulationOn its surface.The uniform condensation of methane on the surface will reduce the contrast of albedo and cover up all red tolin deposits.[15]
Even though Eris is three times as far from the sun as Pluto, it may be close enough to the sun that the surface may warm enough to sublimate some of the ice.Because methane is a highly volatile substance, its existence indicates that Eris has been in the remote region of the solar system, where the temperature is enough to make methane ice persist, or there is methane inside the celestial body to supplement the methane vapor escaping from the atmosphere.This is contrary to the observation result of another discovered Neptune object, Pregod, which found water ice rather than methane.[43]
Comparison of infrared spectrum of Eris (red) and Pluto (black)
Astronomical application
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In 2005, the Keck telescope in Hawaiiadaptive optics The team uses new equipmentLaser guide starThe adaptive optics system has observed the four brightest Neptune objects (Pluto, Orion, Pregnancy and Erin).[44]The picture taken on September 10 shows that there is a satellite in orbit near Eris.In order to keep consistent with the nickname of "Xena", which was first used by Eris, Brown's team named the satellite "Gabrielle" (a close friend of "Xena").When Eris was officially named by the International Astronomical Union, Eris was named after Dysnomia, the daughter of Eris.Brown said he chose the name because it was similar to his wife's name Diane.The use of the name of Lawlessness also coincides with the surname of Lucy Lawless, who plays the soldier princess "Zina" in the TV series.[45]
In the 2010s, after New Horizons successfully flew over Pluto, several projects carried out research on the follow-up exploration of the Kuiper Belt, including the evaluation of the candidate star Eris.[46]It is calculated that if the probe is launched on April 3, 2032 or April 7, 2044, the exploration mission of using Jupiter's gravitational acceleration to fly over Eris may take 24.66 years.When the probe arrives, the distance between the Eris star and the sun will be 92.03 or 90.19 astronomical units.[18]
