DioLiu/Test2 · Datasets at Hugging Face

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= = Track listing = =

( Credits lifted from the album liner notes )

= = Personnel = =

( Credits lifted from the album liner notes )

= = Charts and certifications = =


= = = Album charts = = =


= = = Song charts = = =


= = = Certifications = = =

\| }


= Ceres ( dwarf planet ) =

Ceres ( / ˈsɪəriːz / ; minor @-@ planet designation : 1 Ceres ) is the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter . Its diameter is approximately 945 kilometers ( 587 miles ) , making it the largest of the minor planets within the orbit of Neptune . The thirty @-@ third @-@ largest known body in the Solar System , it is the only one identified orbiting entirely within the orbit of Neptune that is a dwarf planet . Composed of rock and ice , Ceres is estimated to comprise approximately one third of the mass of the entire asteroid belt . Ceres is the only object in the asteroid belt known to be rounded by its own gravity . From Earth , the apparent magnitude of Ceres ranges from 6 @.@ 7 to 9 @.@ 3 , and hence even at its brightest , it is too dim to be seen with the naked eye , except under extremely dark skies .
Ceres was the first asteroid discovered , by Giuseppe Piazzi at Palermo on 1 January 1801 . It was originally considered a planet , but was reclassified as an asteroid in the 1850s when many other objects in similar orbits were discovered .
Ceres appears to be differentiated into a rocky core and icy mantle , and may have a remnant internal ocean of liquid water under the layer of ice . The surface is probably a mixture of water ice and various hydrated minerals such as carbonates and clay . In January 2014 , emissions of water vapor were detected from several regions of Ceres . This was unexpected , because large bodies in the asteroid belt do not typically emit vapor , a hallmark of comets .
The robotic NASA spacecraft Dawn entered orbit around Ceres on 6 March 2015 . Pictures with a resolution previously unattained were taken during imaging sessions starting in January 2015 as Dawn approached Ceres , showing a cratered surface . Two distinct bright spots ( or high @-@ albedo features ) inside a crater ( different from the bright spots observed in earlier Hubble images ) were seen in a 19 February 2015 image , leading to speculation about a possible cryovolcanic origin or outgassing . On 3 March 2015 , a NASA spokesperson said the spots are consistent with highly reflective materials containing ice or salts , but that cryovolcanism is unlikely . On 11 May 2015 , NASA released a higher @-@ resolution image showing that , instead of one or two spots , there are actually several . On 9 December 2015 , NASA scientists reported that the bright spots on Ceres may be related to a type of salt , particularly a form of brine containing magnesium sulfate hexahydrite ( MgSO4 · 6H2O ) ; the spots were also found to be associated with ammonia @-@ rich clays . In June 2016 , near @-@ infrared spectra of these bright areas were found to be consistent with a large amount of sodium carbonate , ( Na
2CO
3 ) , implying that recent geologic activity was probably involved in the creation of the bright spots .
In October 2015 , NASA released a true color portrait of Ceres made by Dawn .

= = History = =


= = = Discovery = = =

Johann Elert Bode , in 1772 , first suggested that an undiscovered planet could exist between the orbits of Mars and Jupiter . Kepler had already noticed the gap between Mars and Jupiter in 1596 . Bode based his idea on the Titius – Bode law — a now @-@ discredited hypothesis Johann Daniel Titius first proposed in 1766 — observing that there was a regular pattern in the semi @-@ major axes of the orbits of known planets , marred only by the large gap between Mars and Jupiter . The pattern predicted that the missing planet ought to have an orbit with a semi @-@ major axis near 2 @.@ 8 astronomical units ( AU ) . William Herschel 's discovery of Uranus in 1781 near the predicted distance for the next body beyond Saturn increased faith in the law of Titius and Bode , and in 1800 , a group headed by Franz Xaver von Zach , editor of the Monatliche Correspondenz , sent requests to twenty @-@ four experienced astronomers ( dubbed the " celestial police " ) , asking that they combine their efforts and begin a methodical search for the expected planet . Although they did not discover Ceres , they later found several large asteroids .
One of the astronomers selected for the search was Giuseppe Piazzi , a Catholic priest at the Academy of Palermo , Sicily . Before receiving his invitation to join the group , Piazzi discovered Ceres on 1 January 1801 . He was searching for " the 87th [ star ] of the Catalogue of the Zodiacal stars of Mr la Caille " , but found that " it was preceded by another " . Instead of a star , Piazzi had found a moving star @-@ like object , which he first thought was a comet . Piazzi observed Ceres a total of 24 times , the final time on 11 February 1801 , when illness interrupted his observations . He announced his discovery on 24 January 1801 in letters to only two fellow astronomers , his compatriot Barnaba Oriani of Milan and Bode of Berlin . He reported it as a comet but " since its movement is so slow and rather uniform , it has occurred to me several times that it might be something better than a comet " . In April , Piazzi sent his complete observations to Oriani , Bode , and Jérôme Lalande in Paris . The information was published in the September 1801 issue of the Monatliche Correspondenz .
By this time , the apparent position of Ceres had changed ( mostly due to Earth 's orbital motion ) , and was too close to the Sun 's glare for other astronomers to confirm Piazzi 's observations . Toward the end of the year , Ceres should have been visible again , but after such a long time it was difficult to predict its exact position . To recover Ceres , Carl Friedrich Gauss , then 24 years old , developed an efficient method of orbit determination . In only a few weeks , he predicted the path of Ceres and sent his results to von Zach . On 31 December 1801 , von Zach and Heinrich W. M. Olbers found Ceres near the predicted position and thus recovered it .
The early observers were only able to calculate the size of Ceres to within an order of magnitude . Herschel underestimated its diameter as 260 km in 1802 , whereas in 1811 Johann Hieronymus Schröter overestimated it as 2 @,@ 613 km .

= = = Name = = =

Piazzi originally suggested the name Cerere Ferdinandea for his discovery , after the goddess Ceres ( Roman goddess of agriculture , Cerere in Italian , who was believed to have originated in Sicily and whose oldest temple was there ) and King Ferdinand of Sicily . " Ferdinandea " , however , was not acceptable to other nations and was dropped . Ceres was called Hera for a short time in Germany . In Greece , it is called Demeter ( Δήμητρα ) , after the Greek equivalent of the Roman Cerēs ; in English , that name is used for the asteroid 1108 Demeter .
The regular adjectival forms of the name are Cererian and Cererean , derived from the Latin genitive Cereris , but Ceresian is occasionally seen for the goddess ( as in the sickle @-@ shaped Ceresian Lake ) , as is the shorter form Cerean .
The old astronomical symbol of Ceres is a sickle , 〈 ⚳ 〉 ( ) , similar to Venus ' symbol 〈 ♀ 〉 but with a break in the circle . It has a variant 〈〉 , reversed under the influence of the initial letter ' C ' of ' Ceres ' . These were later replaced with the generic asteroid symbol of a numbered disk , 〈 ① 〉 .
Cerium , a rare @-@ earth element discovered in 1803 , was named after Ceres . In the same year another element was also initially named after Ceres , but when cerium was named , its discoverer changed the name to palladium , after the second asteroid , 2 Pallas .

= = = Classification = = =

The categorization of Ceres has changed more than once and has been the subject of some disagreement . Johann Elert Bode believed Ceres to be the " missing planet " he had proposed to exist between Mars and Jupiter , at a distance of 419 million km ( 2 @.@ 8 AU ) from the Sun . Ceres was assigned a planetary symbol , and remained listed as a planet in astronomy books and tables ( along with 2 Pallas , 3 Juno , and 4 Vesta ) for half a century .
As other objects were discovered in the neighborhood of Ceres , it was realized that Ceres represented the first of a new class of objects . In 1802 , with the discovery of 2 Pallas , William Herschel coined the term asteroid ( " star @-@ like " ) for these bodies , writing that " they resemble small stars so much as hardly to be distinguished from them , even by very good telescopes " . As the first such body to be discovered , Ceres was given the designation 1 Ceres under the modern system of minor @-@ planet designations . By the 1860s , the existence of a fundamental difference between asteroids such as Ceres and the major planets was widely accepted , though a precise definition of " planet " was never formulated .
The 2006 debate surrounding Pluto and what constitutes a planet led to Ceres being considered for reclassification as a planet . A proposal before the International Astronomical Union for the definition of a planet would have defined a planet as " a celestial body that ( a ) has sufficient mass for its self @-@ gravity to overcome rigid @-@ body forces so that it assumes a hydrostatic equilibrium ( nearly round ) shape , and ( b ) is in orbit around a star , and is neither a star nor a satellite of a planet " . Had this resolution been adopted , it would have made Ceres the fifth planet in order from the Sun . This never happened , however , and on 24 August 2006 a modified definition was adopted , carrying the additional requirement that a planet must have " cleared the neighborhood around its orbit " . By this definition , Ceres is not a planet because it does not dominate its orbit , sharing it as it does with the thousands of other asteroids in the asteroid belt and constituting only about a third of the mass of the belt . Bodies that met the first proposed definition but not the second , such as Ceres , were instead classified as dwarf planets .
Ceres is the largest object in the asteroid belt . It is sometimes assumed that Ceres has been reclassified as a dwarf planet , and that it is therefore no longer considered an asteroid . For example , a news update at Space.com spoke of " Pallas , the largest asteroid , and Ceres , the dwarf planet formerly classified as an asteroid " , whereas an IAU question @-@ and @-@ answer posting states , " Ceres is ( or now we can say it was ) the largest asteroid " , though it then speaks of " other asteroids " crossing Ceres ' path and otherwise implies that Ceres is still considered an asteroid . The Minor Planet Center notes that such bodies may have dual designations . The 2006 IAU decision that classified Ceres as a dwarf planet never addressed whether it is or is not an asteroid . Indeed , the IAU has never defined the word ' asteroid ' at all , having preferred the term ' minor planet ' until 2006 , and preferring the terms ' small Solar System body ' and ' dwarf planet ' after 2006 . Lang ( 2011 ) comments " the [ IAU has ] added a new designation to Ceres , classifying it as a dwarf planet . ... By [ its ] definition , Eris , Haumea , Makemake and Pluto , as well as the largest asteroid , 1 Ceres , are all dwarf planets " , and describes it elsewhere as " the dwarf planet – asteroid 1 Ceres " . NASA continues to refer to Ceres as an asteroid , as do various academic textbooks .

= = Orbit = =

Ceres follows an orbit between Mars and Jupiter , within the asteroid belt , with a period of 4 @.@ 6 Earth years . The orbit is moderately inclined ( i
= 10 @.@ 6 ° compared to 7 ° for Mercury and 17 ° for Pluto ) and moderately eccentric ( e =
0 @.@ 08 compared to 0 @.@ 09 for Mars ) .
The diagram illustrates the orbits of Ceres ( blue ) and several planets ( white and gray ) . The segments of orbits below the ecliptic are plotted in darker colors , and the orange plus sign is the Sun 's location . The top left diagram is a polar view that shows the location of Ceres in the gap between Mars and Jupiter . The top right is a close @-@ up demonstrating the locations of the perihelia ( q ) and aphelia ( Q ) of Ceres and Mars . In this diagram ( but not in general ) , the perihelion of Mars is on the opposite side of the Sun from those of Ceres and several of the large main @-@ belt asteroids , including 2 Pallas and 10 Hygiea . The bottom diagram is a side view showing the inclination of the orbit of Ceres compared to the orbits of Mars and Jupiter .
Ceres was once thought to be a member of an asteroid family . The asteroids of this family share similar proper orbital elements , which may indicate a common origin through an asteroid collision some time in the past . Ceres was later found to have spectral properties different from other members of the family , which is now called the Gefion family after the next @-@ lowest @-@ numbered family member , 1272 Gefion . Ceres appears to be merely an interloper in the Gefion family , coincidentally having similar orbital elements but not a common origin .

= = = Resonances = = =

Ceres is in a near @-@ 1 : 1 mean @-@ motion orbital resonance with Pallas ( their proper orbital periods differ by 0 @.@ 2 % ) . However , a true resonance between the two would be unlikely ; due to their small masses relative to their large separations , such relationships among asteroids are very rare . Nevertheless , Ceres is able to capture other asteroids into temporary 1 : 1 resonant orbital relationships ( making them temporary trojans ) for periods up to 2 million years or more ; fifty such objects have been identified .

= = = Transits of planets from Ceres = = =

Mercury , Venus , Earth , and Mars can all appear to cross the Sun , or transit it , from a vantage point on Ceres . The most common transits are those of Mercury , which usually happen every few years , most recently in 2006 and 2010 . The most recent transit of Venus was in 1953 , and the next will be in 2051 ; the corresponding dates are 1814 and 2081 for transits of Earth , and 767 and 2684 for transits of Mars .

= = Rotation and axial tilt = =

The rotation period of Ceres ( the Cererian day ) is 9 hours and 4 minutes . It has a small axial tilt of 4 ° . This is nevertheless large enough for Ceres 's polar regions to contain permanently shadowed craters that are expected to act as cold traps and accumulate water ice over time , similar to the situation on the Moon and Mercury . About 0 @.@ 14 % of water molecules released from the surface are expected to end up in the traps , hopping an average of 3 times before escaping or being trapped .

= = Geology = =

Ceres has a mass of 9 @.@ 39 × 1020 kg as determined from the Dawn spacecraft . With this mass Ceres comprises approximately a third of the estimated total 3 @.@ 0 ± 0 @.@ 2 × 1021 kg mass of the asteroid belt , which is in turn approximately 4 % of the mass of the Moon . Ceres is massive enough to give it a nearly spherical , equilibrium shape . Among Solar System bodies , Ceres is intermediate in size between the smaller Vesta and the larger Tethys . Its surface area is approximately the same as the land area of India or Argentina .

= = = Surface = = =

The surface composition of Ceres is broadly similar to that of C @-@ type asteroids . Some differences do exist . The ubiquitous features in Ceres ' IR spectrum are those of hydrated materials , which indicate the presence of significant amounts of water in its interior . Other possible surface constituents include iron @-@ rich clay minerals ( cronstedtite ) and carbonate minerals ( dolomite and siderite ) , which are common minerals in carbonaceous chondrite meteorites . The spectral features of carbonates and clay minerals are usually absent in the spectra of other C @-@ type asteroids . Sometimes Ceres is classified as a G @-@ type asteroid .
Ceres ' surface is relatively warm . The maximum temperature with the Sun overhead was estimated from measurements to be 235 K ( approximately − 38 ° C , − 36 ° F ) on 5 May 1991 . Ice is unstable at this temperature . Material left behind by the sublimation of surface ice could explain the dark surface of Ceres compared to the icy moons of the outer Solar System .

= = = = Observations prior to Dawn = = = =

Prior to the Dawn mission , only a few surface features had been unambiguously detected on Ceres . High @-@ resolution ultraviolet Hubble Space Telescope images taken in 1995 showed a dark spot on its surface , which was nicknamed " Piazzi " in honor of the discoverer of Ceres . This was thought to be a crater . Later near @-@ infrared images with a higher resolution taken over a whole rotation with the Keck telescope using adaptive optics showed several bright and dark features moving with Ceres ' rotation . Two dark features had circular shapes and were presumed to be craters ; one of them was observed to have a bright central region , whereas another was identified as the " Piazzi " feature . Visible @-@ light Hubble Space Telescope images of a full rotation taken in 2003 and 2004 showed eleven recognizable surface features , the natures of which were then undetermined . One of these features corresponds to the " Piazzi " feature observed earlier .
These last observations indicated that the north pole of Ceres pointed in the direction of right ascension 19 h 24 min ( 291 ° ) , declination + 59 ° , in the constellation Draco , resulting in an axial tilt of approximately 3 ° . Dawn later determined that the north polar axis actually points at right ascension 19 h 25 m 40 @.@ 3 s ( 291 @.@ 418 ° ) , declination + 66 ° 45 ' 50 " ( about 1 @.@ 5 degrees from Delta Draconis ) , which means an axial tilt of 4 ° .

= = = = Observations by Dawn = = = =

Dawn revealed a large number of craters with low relief , indicating that they lie over a relatively soft surface , probably of water ice . One crater , with extremely low relief , is 270 km ( 170 mi ) in diameter , reminiscent of large , flat craters on Tethys and Iapetus . An unexpectedly large number of Cererian craters have central pits , and many have central peaks . Several bright spots have been observed by Dawn , the brightest spot ( " Spot 5 " ) located in the middle of an 80 @-@ kilometer ( 50 mi ) crater called Occator . From images taken of Ceres on 4 May 2015 , the secondary bright spot was revealed to actually be a group of scattered bright areas , possibly as many as ten . These bright features have an albedo of approximately 40 % that are caused by a substance on the surface , possibly ice or salts , reflecting sunlight . A haze periodically appears above Spot 5 , the best known bright spot , supporting the hypothesis that some sort of outgassing or sublimating ice formed the bright spots . In March 2016 , Dawn found definitive evidence of water molecules on the surface of Ceres at Oxo crater . JPL states : " This water could be bound up in minerals or , alternatively , it could take the form of ice . "
On 9 December 2015 , NASA scientists reported that the bright spots on Ceres may be related to a type of salt , particularly a form of brine containing magnesium sulfate hexahydrite ( MgSO4 · 6H2O ) ; the spots were also found to be associated with ammonia @-@ rich clays . Another team thinks the salts are sodium carbonate .

= = = Internal structure = = =

Ceres ' oblateness is consistent with a differentiated body , a rocky core overlain with an icy mantle . This 100 @-@ kilometer @-@ thick mantle ( 23 % – 28 % of Ceres by mass ; 50 % by volume ) contains up to 200 million cubic kilometers of water , which would be more than the amount of fresh water on Earth . This result is supported by the observations made by the Keck telescope in 2002 and by evolutionary modeling . Also , some characteristics of its surface and history ( such as its distance from the Sun , which weakened solar radiation enough to allow some fairly low @-@ freezing @-@ point components to be incorporated during its formation ) , point to the presence of volatile materials in the interior of Ceres . It has been suggested that a remnant layer of liquid water may have survived to the present under a layer of ice . Measurements taken by Dawn confirm that Ceres is both differentiated and has a shape consistent with hydrostatic equilibrium , which makes Ceres the smallest object confirmed to be in hydrostatic equilibrium , being 600 km smaller and less than half the mass of Saturn 's moon Rhea , the next smallest such object . Modeling has suggested Ceres could have a small metallic core from partial differentiation of its rocky fraction .

= = Track listing = =

( Credits lifted from the album liner notes )

= = Personnel = =

( Credits lifted from the album liner notes )

= = Charts and certifications = =

= = = Album charts = = =

= = = Song charts = = =

= = = Certifications = = =

| }

= Ceres ( dwarf planet ) =

Ceres ( / ˈsɪəriːz / ; minor @-@ planet designation : 1 Ceres ) is the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter . Its diameter is approximately 945 kilometers ( 587 miles ) , making it the largest of the minor planets within the orbit of Neptune . The thirty @-@ third @-@ largest known body in the Solar System , it is the only one identified orbiting entirely within the orbit of Neptune that is a dwarf planet . Composed of rock and ice , Ceres is estimated to comprise approximately one third of the mass of the entire asteroid belt . Ceres is the only object in the asteroid belt known to be rounded by its own gravity . From Earth , the apparent magnitude of Ceres ranges from 6 @.@ 7 to 9 @.@ 3 , and hence even at its brightest , it is too dim to be seen with the naked eye , except under extremely dark skies .

Ceres was the first asteroid discovered , by Giuseppe Piazzi at Palermo on 1 January 1801 . It was originally considered a planet , but was reclassified as an asteroid in the 1850s when many other objects in similar orbits were discovered .

Ceres appears to be differentiated into a rocky core and icy mantle , and may have a remnant internal ocean of liquid water under the layer of ice . The surface is probably a mixture of water ice and various hydrated minerals such as carbonates and clay . In January 2014 , emissions of water vapor were detected from several regions of Ceres . This was unexpected , because large bodies in the asteroid belt do not typically emit vapor , a hallmark of comets .

The robotic NASA spacecraft Dawn entered orbit around Ceres on 6 March 2015 . Pictures with a resolution previously unattained were taken during imaging sessions starting in January 2015 as Dawn approached Ceres , showing a cratered surface . Two distinct bright spots ( or high @-@ albedo features ) inside a crater ( different from the bright spots observed in earlier Hubble images ) were seen in a 19 February 2015 image , leading to speculation about a possible cryovolcanic origin or outgassing . On 3 March 2015 , a NASA spokesperson said the spots are consistent with highly reflective materials containing ice or salts , but that cryovolcanism is unlikely . On 11 May 2015 , NASA released a higher @-@ resolution image showing that , instead of one or two spots , there are actually several . On 9 December 2015 , NASA scientists reported that the bright spots on Ceres may be related to a type of salt , particularly a form of brine containing magnesium sulfate hexahydrite ( MgSO4 · 6H2O ) ; the spots were also found to be associated with ammonia @-@ rich clays . In June 2016 , near @-@ infrared spectra of these bright areas were found to be consistent with a large amount of sodium carbonate , ( Na

2CO

3 ) , implying that recent geologic activity was probably involved in the creation of the bright spots .

In October 2015 , NASA released a true color portrait of Ceres made by Dawn .

= = History = =

= = = Discovery = = =

Johann Elert Bode , in 1772 , first suggested that an undiscovered planet could exist between the orbits of Mars and Jupiter . Kepler had already noticed the gap between Mars and Jupiter in 1596 . Bode based his idea on the Titius – Bode law — a now @-@ discredited hypothesis Johann Daniel Titius first proposed in 1766 — observing that there was a regular pattern in the semi @-@ major axes of the orbits of known planets , marred only by the large gap between Mars and Jupiter . The pattern predicted that the missing planet ought to have an orbit with a semi @-@ major axis near 2 @.@ 8 astronomical units ( AU ) . William Herschel 's discovery of Uranus in 1781 near the predicted distance for the next body beyond Saturn increased faith in the law of Titius and Bode , and in 1800 , a group headed by Franz Xaver von Zach , editor of the Monatliche Correspondenz , sent requests to twenty @-@ four experienced astronomers ( dubbed the " celestial police " ) , asking that they combine their efforts and begin a methodical search for the expected planet . Although they did not discover Ceres , they later found several large asteroids .

One of the astronomers selected for the search was Giuseppe Piazzi , a Catholic priest at the Academy of Palermo , Sicily . Before receiving his invitation to join the group , Piazzi discovered Ceres on 1 January 1801 . He was searching for " the 87th [ star ] of the Catalogue of the Zodiacal stars of Mr la Caille " , but found that " it was preceded by another " . Instead of a star , Piazzi had found a moving star @-@ like object , which he first thought was a comet . Piazzi observed Ceres a total of 24 times , the final time on 11 February 1801 , when illness interrupted his observations . He announced his discovery on 24 January 1801 in letters to only two fellow astronomers , his compatriot Barnaba Oriani of Milan and Bode of Berlin . He reported it as a comet but " since its movement is so slow and rather uniform , it has occurred to me several times that it might be something better than a comet " . In April , Piazzi sent his complete observations to Oriani , Bode , and Jérôme Lalande in Paris . The information was published in the September 1801 issue of the Monatliche Correspondenz .

By this time , the apparent position of Ceres had changed ( mostly due to Earth 's orbital motion ) , and was too close to the Sun 's glare for other astronomers to confirm Piazzi 's observations . Toward the end of the year , Ceres should have been visible again , but after such a long time it was difficult to predict its exact position . To recover Ceres , Carl Friedrich Gauss , then 24 years old , developed an efficient method of orbit determination . In only a few weeks , he predicted the path of Ceres and sent his results to von Zach . On 31 December 1801 , von Zach and Heinrich W. M. Olbers found Ceres near the predicted position and thus recovered it .

The early observers were only able to calculate the size of Ceres to within an order of magnitude . Herschel underestimated its diameter as 260 km in 1802 , whereas in 1811 Johann Hieronymus Schröter overestimated it as 2 @,@ 613 km .

= = = Name = = =

Piazzi originally suggested the name Cerere Ferdinandea for his discovery , after the goddess Ceres ( Roman goddess of agriculture , Cerere in Italian , who was believed to have originated in Sicily and whose oldest temple was there ) and King Ferdinand of Sicily . " Ferdinandea " , however , was not acceptable to other nations and was dropped . Ceres was called Hera for a short time in Germany . In Greece , it is called Demeter ( Δήμητρα ) , after the Greek equivalent of the Roman Cerēs ; in English , that name is used for the asteroid 1108 Demeter .

The regular adjectival forms of the name are Cererian and Cererean , derived from the Latin genitive Cereris , but Ceresian is occasionally seen for the goddess ( as in the sickle @-@ shaped Ceresian Lake ) , as is the shorter form Cerean .

The old astronomical symbol of Ceres is a sickle , 〈 ⚳ 〉 ( ) , similar to Venus ' symbol 〈 ♀ 〉 but with a break in the circle . It has a variant 〈〉 , reversed under the influence of the initial letter ' C ' of ' Ceres ' . These were later replaced with the generic asteroid symbol of a numbered disk , 〈 ① 〉 .

Cerium , a rare @-@ earth element discovered in 1803 , was named after Ceres . In the same year another element was also initially named after Ceres , but when cerium was named , its discoverer changed the name to palladium , after the second asteroid , 2 Pallas .

= = = Classification = = =

The categorization of Ceres has changed more than once and has been the subject of some disagreement . Johann Elert Bode believed Ceres to be the " missing planet " he had proposed to exist between Mars and Jupiter , at a distance of 419 million km ( 2 @.@ 8 AU ) from the Sun . Ceres was assigned a planetary symbol , and remained listed as a planet in astronomy books and tables ( along with 2 Pallas , 3 Juno , and 4 Vesta ) for half a century .

As other objects were discovered in the neighborhood of Ceres , it was realized that Ceres represented the first of a new class of objects . In 1802 , with the discovery of 2 Pallas , William Herschel coined the term asteroid ( " star @-@ like " ) for these bodies , writing that " they resemble small stars so much as hardly to be distinguished from them , even by very good telescopes " . As the first such body to be discovered , Ceres was given the designation 1 Ceres under the modern system of minor @-@ planet designations . By the 1860s , the existence of a fundamental difference between asteroids such as Ceres and the major planets was widely accepted , though a precise definition of " planet " was never formulated .

The 2006 debate surrounding Pluto and what constitutes a planet led to Ceres being considered for reclassification as a planet . A proposal before the International Astronomical Union for the definition of a planet would have defined a planet as " a celestial body that ( a ) has sufficient mass for its self @-@ gravity to overcome rigid @-@ body forces so that it assumes a hydrostatic equilibrium ( nearly round ) shape , and ( b ) is in orbit around a star , and is neither a star nor a satellite of a planet " . Had this resolution been adopted , it would have made Ceres the fifth planet in order from the Sun . This never happened , however , and on 24 August 2006 a modified definition was adopted , carrying the additional requirement that a planet must have " cleared the neighborhood around its orbit " . By this definition , Ceres is not a planet because it does not dominate its orbit , sharing it as it does with the thousands of other asteroids in the asteroid belt and constituting only about a third of the mass of the belt . Bodies that met the first proposed definition but not the second , such as Ceres , were instead classified as dwarf planets .

Ceres is the largest object in the asteroid belt . It is sometimes assumed that Ceres has been reclassified as a dwarf planet , and that it is therefore no longer considered an asteroid . For example , a news update at Space.com spoke of " Pallas , the largest asteroid , and Ceres , the dwarf planet formerly classified as an asteroid " , whereas an IAU question @-@ and @-@ answer posting states , " Ceres is ( or now we can say it was ) the largest asteroid " , though it then speaks of " other asteroids " crossing Ceres ' path and otherwise implies that Ceres is still considered an asteroid . The Minor Planet Center notes that such bodies may have dual designations . The 2006 IAU decision that classified Ceres as a dwarf planet never addressed whether it is or is not an asteroid . Indeed , the IAU has never defined the word ' asteroid ' at all , having preferred the term ' minor planet ' until 2006 , and preferring the terms ' small Solar System body ' and ' dwarf planet ' after 2006 . Lang ( 2011 ) comments " the [ IAU has ] added a new designation to Ceres , classifying it as a dwarf planet . ... By [ its ] definition , Eris , Haumea , Makemake and Pluto , as well as the largest asteroid , 1 Ceres , are all dwarf planets " , and describes it elsewhere as " the dwarf planet – asteroid 1 Ceres " . NASA continues to refer to Ceres as an asteroid , as do various academic textbooks .

= = Orbit = =

Ceres follows an orbit between Mars and Jupiter , within the asteroid belt , with a period of 4 @.@ 6 Earth years . The orbit is moderately inclined ( i

= 10 @.@ 6 ° compared to 7 ° for Mercury and 17 ° for Pluto ) and moderately eccentric ( e =

0 @.@ 08 compared to 0 @.@ 09 for Mars ) .

The diagram illustrates the orbits of Ceres ( blue ) and several planets ( white and gray ) . The segments of orbits below the ecliptic are plotted in darker colors , and the orange plus sign is the Sun 's location . The top left diagram is a polar view that shows the location of Ceres in the gap between Mars and Jupiter . The top right is a close @-@ up demonstrating the locations of the perihelia ( q ) and aphelia ( Q ) of Ceres and Mars . In this diagram ( but not in general ) , the perihelion of Mars is on the opposite side of the Sun from those of Ceres and several of the large main @-@ belt asteroids , including 2 Pallas and 10 Hygiea . The bottom diagram is a side view showing the inclination of the orbit of Ceres compared to the orbits of Mars and Jupiter .

Ceres was once thought to be a member of an asteroid family . The asteroids of this family share similar proper orbital elements , which may indicate a common origin through an asteroid collision some time in the past . Ceres was later found to have spectral properties different from other members of the family , which is now called the Gefion family after the next @-@ lowest @-@ numbered family member , 1272 Gefion . Ceres appears to be merely an interloper in the Gefion family , coincidentally having similar orbital elements but not a common origin .

= = = Resonances = = =

Ceres is in a near @-@ 1 : 1 mean @-@ motion orbital resonance with Pallas ( their proper orbital periods differ by 0 @.@ 2 % ) . However , a true resonance between the two would be unlikely ; due to their small masses relative to their large separations , such relationships among asteroids are very rare . Nevertheless , Ceres is able to capture other asteroids into temporary 1 : 1 resonant orbital relationships ( making them temporary trojans ) for periods up to 2 million years or more ; fifty such objects have been identified .

= = = Transits of planets from Ceres = = =

Mercury , Venus , Earth , and Mars can all appear to cross the Sun , or transit it , from a vantage point on Ceres . The most common transits are those of Mercury , which usually happen every few years , most recently in 2006 and 2010 . The most recent transit of Venus was in 1953 , and the next will be in 2051 ; the corresponding dates are 1814 and 2081 for transits of Earth , and 767 and 2684 for transits of Mars .

= = Rotation and axial tilt = =

The rotation period of Ceres ( the Cererian day ) is 9 hours and 4 minutes . It has a small axial tilt of 4 ° . This is nevertheless large enough for Ceres 's polar regions to contain permanently shadowed craters that are expected to act as cold traps and accumulate water ice over time , similar to the situation on the Moon and Mercury . About 0 @.@ 14 % of water molecules released from the surface are expected to end up in the traps , hopping an average of 3 times before escaping or being trapped .

= = Geology = =

Ceres has a mass of 9 @.@ 39 × 1020 kg as determined from the Dawn spacecraft . With this mass Ceres comprises approximately a third of the estimated total 3 @.@ 0 ± 0 @.@ 2 × 1021 kg mass of the asteroid belt , which is in turn approximately 4 % of the mass of the Moon . Ceres is massive enough to give it a nearly spherical , equilibrium shape . Among Solar System bodies , Ceres is intermediate in size between the smaller Vesta and the larger Tethys . Its surface area is approximately the same as the land area of India or Argentina .

= = = Surface = = =

The surface composition of Ceres is broadly similar to that of C @-@ type asteroids . Some differences do exist . The ubiquitous features in Ceres ' IR spectrum are those of hydrated materials , which indicate the presence of significant amounts of water in its interior . Other possible surface constituents include iron @-@ rich clay minerals ( cronstedtite ) and carbonate minerals ( dolomite and siderite ) , which are common minerals in carbonaceous chondrite meteorites . The spectral features of carbonates and clay minerals are usually absent in the spectra of other C @-@ type asteroids . Sometimes Ceres is classified as a G @-@ type asteroid .

Ceres ' surface is relatively warm . The maximum temperature with the Sun overhead was estimated from measurements to be 235 K ( approximately − 38 ° C , − 36 ° F ) on 5 May 1991 . Ice is unstable at this temperature . Material left behind by the sublimation of surface ice could explain the dark surface of Ceres compared to the icy moons of the outer Solar System .

= = = = Observations prior to Dawn = = = =

Prior to the Dawn mission , only a few surface features had been unambiguously detected on Ceres . High @-@ resolution ultraviolet Hubble Space Telescope images taken in 1995 showed a dark spot on its surface , which was nicknamed " Piazzi " in honor of the discoverer of Ceres . This was thought to be a crater . Later near @-@ infrared images with a higher resolution taken over a whole rotation with the Keck telescope using adaptive optics showed several bright and dark features moving with Ceres ' rotation . Two dark features had circular shapes and were presumed to be craters ; one of them was observed to have a bright central region , whereas another was identified as the " Piazzi " feature . Visible @-@ light Hubble Space Telescope images of a full rotation taken in 2003 and 2004 showed eleven recognizable surface features , the natures of which were then undetermined . One of these features corresponds to the " Piazzi " feature observed earlier .

These last observations indicated that the north pole of Ceres pointed in the direction of right ascension 19 h 24 min ( 291 ° ) , declination + 59 ° , in the constellation Draco , resulting in an axial tilt of approximately 3 ° . Dawn later determined that the north polar axis actually points at right ascension 19 h 25 m 40 @.@ 3 s ( 291 @.@ 418 ° ) , declination + 66 ° 45 ' 50 " ( about 1 @.@ 5 degrees from Delta Draconis ) , which means an axial tilt of 4 ° .

= = = = Observations by Dawn = = = =

Dawn revealed a large number of craters with low relief , indicating that they lie over a relatively soft surface , probably of water ice . One crater , with extremely low relief , is 270 km ( 170 mi ) in diameter , reminiscent of large , flat craters on Tethys and Iapetus . An unexpectedly large number of Cererian craters have central pits , and many have central peaks . Several bright spots have been observed by Dawn , the brightest spot ( " Spot 5 " ) located in the middle of an 80 @-@ kilometer ( 50 mi ) crater called Occator . From images taken of Ceres on 4 May 2015 , the secondary bright spot was revealed to actually be a group of scattered bright areas , possibly as many as ten . These bright features have an albedo of approximately 40 % that are caused by a substance on the surface , possibly ice or salts , reflecting sunlight . A haze periodically appears above Spot 5 , the best known bright spot , supporting the hypothesis that some sort of outgassing or sublimating ice formed the bright spots . In March 2016 , Dawn found definitive evidence of water molecules on the surface of Ceres at Oxo crater . JPL states : " This water could be bound up in minerals or , alternatively , it could take the form of ice . "

On 9 December 2015 , NASA scientists reported that the bright spots on Ceres may be related to a type of salt , particularly a form of brine containing magnesium sulfate hexahydrite ( MgSO4 · 6H2O ) ; the spots were also found to be associated with ammonia @-@ rich clays . Another team thinks the salts are sodium carbonate .

= = = Internal structure = = =

Ceres ' oblateness is consistent with a differentiated body , a rocky core overlain with an icy mantle . This 100 @-@ kilometer @-@ thick mantle ( 23 % – 28 % of Ceres by mass ; 50 % by volume ) contains up to 200 million cubic kilometers of water , which would be more than the amount of fresh water on Earth . This result is supported by the observations made by the Keck telescope in 2002 and by evolutionary modeling . Also , some characteristics of its surface and history ( such as its distance from the Sun , which weakened solar radiation enough to allow some fairly low @-@ freezing @-@ point components to be incorporated during its formation ) , point to the presence of volatile materials in the interior of Ceres . It has been suggested that a remnant layer of liquid water may have survived to the present under a layer of ice . Measurements taken by Dawn confirm that Ceres is both differentiated and has a shape consistent with hydrostatic equilibrium , which makes Ceres the smallest object confirmed to be in hydrostatic equilibrium , being 600 km smaller and less than half the mass of Saturn 's moon Rhea , the next smallest such object . Modeling has suggested Ceres could have a small metallic core from partial differentiation of its rocky fraction .