词条 | Main-belt comet | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
释义 |
The first main-belt comet discovered is 7968 Elst–Pizarro. It was discovered in 1979 and was found to have a tail by Eric Elst and Guido Pizarro in 1996 and given the cometary designation 133P/Elst-Pizarro.[4][4] OrbitsUnlike comets, which spend most of their orbit at Jupiter-like or greater distances from the Sun, main-belt comets follow near-circular orbits within the asteroid belt that are undistinguishable from the orbits of many standard asteroids. Although quite a few short-period comets have semimajor axes well within Jupiter's orbit, main-belt comets differ in having small eccentricities and inclinations similar to main-belt asteroids. The first three identified main-belt comets all orbit within the outer part of the asteroid belt.[7] It is not known how an outer Solar System body like the other comets could have made its way into a low-eccentricity orbit typical of the asteroid belt, which is only weakly perturbed by the planets. Hence it is assumed that unlike other comets, the main-belt comets are simply icy asteroids, which formed in an inner Solar System orbit close to their present positions, and that many outer asteroids may be icy.[6] ActivitySome main-belt comets display a cometary dust tail only for a part of their orbit near perihelion. This strongly suggests that volatiles at their surfaces are sublimating, driving off the dust.[7] Activity in 133P/Elst–Pizarro is recurrent, having been observed at each of the last three perihelia.[4] The activity persists for a month or several[6] out of each 5-6 year orbit, and is presumably due to ice being uncovered by minor impacts in the last 100 to 1000 years.[6] These impacts are suspected to excavate these subsurface pockets of volatile material helping to expose them to solar radiation.[6] When discovered in January 2010, P/2010 A2 (LINEAR) was initially given a cometary designation and considered a member of this group,[8] but P/2010 A2 is now thought to be the remnant of an asteroid-on-asteroid impact.[9][10] Observations of (596) Scheila indicated that large amounts of dust were kicked up by the impact of another asteroid of approximately 35 meters in diameter. P/2013 R3In October 2013, observations of P/2013 R3, taken with the 10.4 m Gran Telescopio Canarias on the island of La Palma, showed that this comet was breaking apart.[12] Inspection of the stacked CCD images obtained on October 11 and 12 showed that the main-belt comet presented a central bright condensation that was accompanied on its movement by three more fragments, A,B,C. The brightest A fragment was also detected at the reported position in CCD images obtained at the 1.52 m telescope of the Sierra Nevada Observatory in Granada on October 12.[12] NASA reported on a series of images taken by the Hubble Space Telescope between October 29, 2013 and January 14, 2014 that show the increasing separation of the four main bodies.[13] The Yarkovsky–O'Keefe–Radzievskii–Paddack effect, caused by sunlight, increased the spin rate until the centrifugal force caused the rubble pile to separate.[13]CompositionIt has been hypothesized that main-belt comets may have been the source of Earth's water, because the deuterium–hydrogen ratio of Earth's oceans is too low for classical comets to have been the principal source.[14] European scientists have proposed a sample-return mission from a MBC called Caroline to analyse the content of volatiles and collect dust samples.[7] MembersThe term 'main-belt comet' is a classification based on orbit and the presence of an extended morphology. It does not imply that these objects are comets or that the material surrounding their nuclei was ejected by the sublimation of volatiles, as on comets. Identified members of this morphology class include:
ExplorationCastalia is a proposed mission concept for a robotic spacecraft to explore 133P/Elst–Pizarro and make the first in situ measurements of water in the asteroid belt, and thus, help solve the mystery of the origin of Earth's water.[16] The lead is Colin Snodgrass, from The Open University in the UK. Castalia was proposed in 2015 and 2016 to the European Space Agency within the Cosmic Vision programme missions M4 and M5, but it was not selected. The team continues to mature the mission concept and science objectives.[16] Because of the construction time required and orbital dynamics, a launch date of October 2028 was proposed.[16]See also
References1. ^{{cite web |title=JPL "Main-belt Asteroid" Orbit Classification |publisher=JPL Solar System Dynamics |url=http://ssd.jpl.nasa.gov/sbdb_help.cgi?class=MBA |accessdate=2010-12-15}} 2. ^{{cite news |last1=Chang |first1=Kenneth |last2=Stirone |first2=Shannon |title=The Asteroid Was Shooting Rocks Into Space. ‘Were We Safe in Orbit?’ - NASA’s Osiris-Rex and Japan’s Hayabusa2 spacecraft reached the space rocks they are surveying last year, and scientists from both teams announced early findings on Tuesday (03/19/2019) |url=https://www.nytimes.com/2019/03/19/science/bennu-ryugu-asteroids.html |date=19 March 2019 |work=The New York Times |accessdate=21 March 2019 }} 3. ^{{cite web |title=Hubble Observes Six Tails from an Unusual Asteroid|publisher=Space Telescope Science Institute (STScI), official YouTube channel for the Hubble Space Telescope|url=https://www.youtube.com/watch?v=CGgRNWUFfZ0 |accessdate=2014-11-15}} 4. ^{{cite web|last=Hsieh|first=Henry|title=133P/Elst-Pizarro|url=http://www.ifa.hawaii.edu/~hsieh/elstpiz.shtml|publisher=UH Institute for Astronomy|accessdate=22 June 2012|date=January 20, 2004|deadurl=yes|archiveurl=https://web.archive.org/web/20111026205338/http://www.ifa.hawaii.edu/~hsieh/elstpiz.shtml|archivedate=26 October 2011|df=}} 5. ^{{cite web |last1=Harrington |first1=J.D. |last2=Villard |first2=Ray |title=RELEASE 14-060 NASA's Hubble Telescope Witnesses Asteroid's Mysterious Disintegration |url=http://www.nasa.gov/press/2014/march/nasas-hubble-telescope-witnesses-asteroids-mysterious-disintegration-1 |date=6 March 2014 |work=NASA |accessdate=6 March 2014 }} 6. ^1 2 3 4 5 {{cite web|date=May 2010 |title=Main Belt Comets |publisher=Hawaii |author=Henry H. Hsieh |url=http://www.ifa.hawaii.edu/~hsieh/mbcs.shtml |archive-url=https://web.archive.org/web/20110806021852/http://www.ifa.hawaii.edu/~hsieh/mbcs.shtml |dead-url=yes |archive-date=2011-08-06 |accessdate=2010-12-15 }} (older 2010 site) {{webarchive|url=https://web.archive.org/web/20090810052739/http://star.pst.qub.ac.uk/~hhh/mbcs.shtml |date=2009-08-10 }} 7. ^1 [https://ac.els-cdn.com/S0273117718301741/1-s2.0-S0273117718301741-main.pdf?_tid=60729ad6-8e38-4774-a5a4-cb1535560808&acdnat=1523207512_194ea87998b5bd4a360bee5af6739f73 The proposed Caroline ESA M3 mission to a Main Belt Comet]. Geraint H. Jones, Jessica Agarwal, Neil Bowles, Mark Burchell, Andrew J. Coates, Alan Fitzsimmons, Amara Graps, Henry H. Hsieh, Carey M. Lisse, Stephen C. Lowry, Adam Masters, Colin Snodgrass, Cecilia Tubiana. Advances in Space Research. 25 February 2018. {{doi|10.1016/j.asr.2018.02.032}} 8. ^MPEC 2010-A51 : COMET P/2010 A2 (LINEAR) 9. ^{{cite journal | last1 = Jewitt | first1 = David | last2 = Weaver | first2 = Harold | last3 = Agarwal | first3 = Jessica | last4 = Mutchler | first4 = Max | last5 = Drahus | first5 = Michal | title = A recent disruption of the main-belt asteroid P/2010?A2 | journal = Nature | volume = 467 | pages = 817–9 | date = 2010 | doi = 10.1038/nature09456|bibcode = 2010Natur.467..817J | issue=7317 | pmid=20944743}} 10. ^{{cite journal | last1 = Snodgrass | first1 = Colin | last2 = Tubiana | first2 = Cecilia | last3 = Vincent | first3 = Jean-Baptiste | last4 = Sierks | first4 = Holger | last5 = Hviid | first5 = Stubbe | last6 = Moissl | first6 = Richard | last7 = Boehnhardt | first7 = Hermann | last8 = Barbieri | first8 = Cesare | last9 = Koschny | first9 = Detlef | last10 = Lamy | first10 = Philippe | last11 = Rickman | first11 = Hans | last12 = Rodrigo | first12 = Rafael | last13 = Carry | first13 = Benoît | last14 = Lowry | first14 = Stephen C. | last15 = Laird | first15 = Ryan J. M. | last16 = Weissman | first16 = Paul R. | last17 = Fitzsimmons | first17 = Alan | last18 = Marchi | first18 = Simone | last19 = a’Hearn | first19 = M. | last20 = Angrilli | first20 = F. | last21 = Barucci | first21 = A. | last22 = Bertaux | first22 = J.-L. | last23 = Cremonese | first23 = G. | last24 = Da Deppo | first24 = V. | last25 = Davidsson | first25 = B. | last26 = Debei | first26 = S. | last27 = De Cecco | first27 = M. | last28 = Fornasier | first28 = S. | last29 = Gutiérrez | first29 = P. | last30 = Ip | first30 = W.-H. | title = A collision in 2009 as the origin of the debris trail of asteroid P/2010?A2 | journal = Nature | volume = 467 | pages = 814–6 | date = 2010 | doi = 10.1038/nature09453 | pmid=20944742 | issue=7317| display-authors = 8 |arxiv = 1010.2883 |bibcode = 2010Natur.467..814S }} 11. ^{{cite news|title=Hubble witnesses an asteroid mysteriously disintegrating|url=http://www.spacetelescope.org/news/heic1405/|accessdate=12 March 2014|newspaper=ESA / HUBBLE}} 12. ^1 {{cite web|first=Javier|last=Licandro|title=Main Belt Comet P/2013 R3 is breaking apart|url=http://www.iac.es/divulgacion.php?op1=16&id=816&lang=en&img=1051|publisher=IAC Press Release|accessdate=17 October 2013}} 13. ^1 https://science.nasa.gov/science-news/science-at-nasa/2014/06mar_asteroid/ 14. ^Main-Belt Comets May Have Been Source Of Earths Water, Space Daily, Mar 23, (2006). 15. ^1 2 {{cite web |title=Main Belt Comets |publisher=UCLA, Department of Earth and Space Sciences |author=David Jewitt |url=http://www2.ess.ucla.edu/~jewitt/mbc.html |accessdate=2010-12-15}} 16. ^1 2 [https://www.sciencedirect.com/science/article/pii/S0273117717306622 The Castalia mission to Main Belt Comet 133P/Elst-Pizarro]. C. Snodgrass, G. H. Jones, H. Boehnhardt, A. Gibbings, etal. Advances in Space Research, Volume 62, Issue 8, 15 October 2018, Pages 1947-1976. {{doi|10.1016/j.asr.2017.09.011}}. External links
2 : Comets|Main-belt comets |
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