View source for Active asteroid

{{short description|Bodies orbiting within the main asteroid belt which have shown cometary activity}}
[[File:596 Scheila, 5 minute exposure, Dec. 12, 2010.jpg|250px|thumb|right|Asteroid [[596 Scheila]] displaying a comet-like appearance on 12 December 2010]]
[[File:Aftermath of DART Collision with Dimorphos Captured_by_SOAR_Telescope (noirlab2223a).jpg|thumb|Dust ejecta and tail from the aftermath of the [[Double Asteroid Redirection Test]]'s impact on the [[minor-planet moon|asteroid moon]] [[Dimorphos]], as seen by the [[Southern Astrophysical Research Telescope]] in 2022]]
'''Active asteroids''' are [[Small Solar System body|small Solar System bodies]] that have [[asteroid]]-like orbits but show [[comet]]-like visual characteristics.<ref name="NYT-20221118">{{cite news |last=Andrews |first=Robin George |title=The Mysterious Comets That Hide in the Asteroid Belt - Comets normally fly in from the far reaches of space. Yet astronomers have found them seemingly misplaced in the asteroid belt. Why are they there? |url=https://www.nytimes.com/2022/11/18/science/comet-asteroid-belt-space.html |date=18 November 2022 |work=[[The New York Times]] |accessdate=18 November 2022 }}</ref> That is, they show a [[Coma (cometary)|coma]], [[comet tail|tail]], or other visual evidence of mass-loss (like a comet), but their orbits remain within [[Jupiter]]'s orbit (like an asteroid).<ref name="Jewitt"/><ref name="JHA15" /> These bodies were originally designated '''main-belt comets''' (MBCs) in 2006 by astronomers [[David Jewitt]] and [[Henry Hsieh (astronomer)|Henry Hsieh]], but this name implies they are necessarily icy in composition like a comet and that they only exist within the [[asteroid belt|main-belt]], whereas the growing population of active asteroids shows that this is not always the case.<ref name="Jewitt">{{cite web |title=The Active Asteroids |publisher=[[UCLA]], Department of Earth and Space Sciences |author=David Jewitt |url=http://www2.ess.ucla.edu/~jewitt/mbc.html |access-date=2020-01-26|author-link=David Jewitt }}</ref><ref name="NYT-20190319">{{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]] |access-date=21 March 2019 }}</ref><ref>{{cite web |title=Hubble Observes Six Tails from an Unusual Asteroid|date=14 November 2013 |publisher=Space Telescope Science Institute (STScI), official YouTube channel for the Hubble Space Telescope|url=https://www.youtube.com/watch?v=CGgRNWUFfZ0  |archive-url=https://ghostarchive.org/varchive/youtube/20211222/CGgRNWUFfZ0 |archive-date=2021-12-22 |url-status=live|access-date=2014-11-15}}{{cbignore}}</ref>

The first active asteroid discovered is [[7968 Elst–Pizarro]]. It was discovered (as an asteroid) in 1979 but then was found to have a tail by [[Eric Walter Elst|Eric Elst]] and Guido Pizarro in 1996 and given the cometary designation 133P/Elst-Pizarro.<ref name="Jewitt"/><ref name=HH133P>{{cite web|last=Hsieh|first=Henry|title=133P/Elst-Pizarro|url=http://www.ifa.hawaii.edu/~hsieh/elstpiz.shtml|publisher=UH Institute for Astronomy|access-date=22 June 2012|date=January 20, 2004|url-status=dead|archive-url=https://web.archive.org/web/20111026205338/http://www.ifa.hawaii.edu/~hsieh/elstpiz.shtml|archive-date=26 October 2011}}</ref>

== Orbits ==
Unlike [[Comet#Orbital characteristics|comets]], which spend most of their orbit at Jupiter-like or greater distances from the Sun, active asteroids follow orbits within the orbit of [[Jupiter]] that are often indistinguishable from the orbits of standard [[Asteroid#Distribution within the Solar System|asteroids]]. [[David Jewitt|Jewitt]] defines active asteroids as those bodies that, in addition to having visual evidence of mass loss, have an orbit with:<ref name="JHA15" />
* [[semi-major axis]] a < a<sub>Jupiter</sub> (5.20 [[astronomical unit|AU]])
* [[Tisserand parameter]] with respect to Jupiter T<sub>J</sub> > 3.08

Jewitt chooses 3.08 as the Tisserand parameter to separate asteroids and comets instead of 3.0 (the Tisserand parameter of Jupiter itself) to avoid ambiguous cases caused by the real [[Solar System]] deviating from an idealized [[restricted three-body problem]].<ref name="JHA15" />

The first three identified active asteroids all orbit within the outer part of the [[asteroid belt]].<ref name="HHsieh">{{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 |url-status=dead |archive-date=2011-08-06 |access-date=2010-12-15 }} [http://star.pst.qub.ac.uk/~hhh/mbcs.shtml (older 2010 site)] {{webarchive|url=https://web.archive.org/web/20090810052739/http://star.pst.qub.ac.uk/~hhh/mbcs.shtml |date=2009-08-10 }}</ref>

== Activity ==
[[File:14060-Asteroid-P2013R3-Disintegration-20140306.jpg|thumb|right|300px|Disintegration of asteroid [[P/2013 R3]] observed by the [[Hubble Space Telescope]] (6 March 2014).<ref name="NASA-20140306">{{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]] |access-date=6 March 2014 }}</ref><ref>{{cite news|title=Hubble witnesses an asteroid mysteriously disintegrating|url=http://www.spacetelescope.org/news/heic1405/|access-date=12 March 2014|newspaper=ESA / HUBBLE}}</ref>]] 
Some active asteroids display a cometary dust tail only for a part of their orbit near [[Apsis|perihelion]]. This strongly suggests that volatiles at their surfaces are sublimating, driving off the dust.<ref name=Caroline>[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}}</ref> Activity in [[133P/Elst–Pizarro]] is recurrent, having been observed at each of the last three perihelia.<ref name="Jewitt"/> The activity persists for a month or several<ref name="HHsieh"/> 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.<ref name="HHsieh"/> These impacts are suspected to excavate these subsurface pockets of [[Volatile (astrogeology)|volatile]] material helping to expose them to [[solar radiation]].<ref name="HHsieh"/>

When discovered in January 2010, [[P/2010 A2|P/2010 A2 (LINEAR)]] was initially given a cometary designation and thought to be showing comet-like sublimation,<ref>[http://www.minorplanetcenter.org/mpec/K10/K10A51.html MPEC 2010-A51 : COMET P/2010 A2 (LINEAR)]</ref> but P/2010 A2 is now thought to be the remnant of an asteroid-on-asteroid impact.<ref>{{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| s2cid = 205222567 }}</ref><ref>{{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 | s2cid = 4330570 }}</ref> 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 R3===
{{Main article|P/2013 R3 (Catalina–PanSTARRS)}}
P/2013 R3 (Catalina–PanSTARRS) was discovered independently by two observers by [[Richard E. Hill]] using the Catalina Sky Survey's 0.68-m Schmidt telescope and by [[Bryce T. Bolin]] using the 1.8-m Pan-STARRS1 telescope on Haleakala.<ref name=HillBolinP2013R3>{{cite journal|first1=R|last1=Hill|first2=B |last2=Bolin|first3=J |last3=Kleyna|first4=L |last4=Denneau|first5=R |last5=Wainscoat|first6=M |last6=Micheli|first7=J |last7=Armstrong|first8=M |last8=Molina|first9=H |last9=Sato|title=CBET #3658 : COMET P/2013 R3 (CATALINA-PANSTARRS)|journal=Central Bureau Electronic Telegrams|year=2013|issue=3658|page=1|url=https://ui.adsabs.harvard.edu/abs/2013CBET.3658....1H/abstract|publisher=[[Central Bureau for Astronomical Telegrams]]|bibcode=2013CBET.3658....1H|access-date=27 September 2013}}</ref> The discovery images taken by [[Pan-STARRS|Pan-STARRS1]] showed the appearance of two distinct sources within 3" of each other combined with a tail enveloping both sources. In October 2013, follow-up 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.<ref name=LicandroP2013>{{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|access-date=17 October 2013}}</ref> 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.<ref name=LicandroP2013/>

[[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.<ref name=NASA20140306>{{Cite web | url=https://science.nasa.gov/science-news/science-at-nasa/2014/06mar_asteroid/ |title = Hubble Witnesses Asteroid's Mysterious Disintegration &#124; Science Mission Directorate}}</ref> The [[Yarkovsky–O'Keefe–Radzievskii–Paddack effect]], caused by sunlight, increased the spin rate until the [[centrifugal force]] caused the [[rubble pile]] to separate.<ref name=NASA20140306/>

===Dimorphos===
{{Main|Dimorphos}}

By smashing into the asteroid moon of the [[binary asteroid]] [[65803 Didymos]], NASA's [[Double Asteroid Redirection Test]] spacecraft made Dimorphos an active asteroid. Scientists had proposed that some active asteroids are the result of impact events, but no one had ever observed the activation of an asteroid. The DART mission activated Dimorphos under precisely known and carefully observed impact conditions, enabling the detailed study of the formation of an active asteroid for the first time.<ref name="nasa-march2023">{{cite web |last1=Furfaro |first1=Emily |title=NASA's DART Data Validates Kinetic Impact as Planetary Defense Method |url=https://www.nasa.gov/feature/nasa-s-dart-data-validates-kinetic-impact-as-planetary-defense-method |website=NASA |access-date=9 March 2023 |date=28 February 2023}} {{PD-notice}}</ref><ref>{{cite journal |last1=Li |first1=Jian-Yang |last2=Hirabayashi |first2=Masatoshi |last3=Farnham |first3=Tony L. |last4=Sunshine |first4=Jessica M. |last5=Knight |first5=Matthew M. |last6=Tancredi |first6=Gonzalo |last7=Moreno |first7=Fernando |last8=Murphy |first8=Brian |last9=Opitom |first9=Cyrielle |last10=Chesley |first10=Steve |last11=Scheeres |first11=Daniel J. |last12=Thomas |first12=Cristina A. |last13=Fahnestock |first13=Eugene G. |last14=Cheng |first14=Andrew F. |last15=Dressel |first15=Linda |last16=Ernst |first16=Carolyn M. |last17=Ferrari |first17=Fabio |last18=Fitzsimmons |first18=Alan |last19=Ieva |first19=Simone |last20=Ivanovski |first20=Stavro L. |last21=Kareta |first21=Teddy |last22=Kolokolova |first22=Ludmilla |last23=Lister |first23=Tim |last24=Raducan |first24=Sabina D. |last25=Rivkin |first25=Andrew S. |last26=Rossi |first26=Alessandro |last27=Soldini |first27=Stefania |last28=Stickle |first28=Angela M. |last29=Vick |first29=Alison |last30=Vincent |first30=Jean-Baptiste |last31=Weaver |first31=Harold A. |last32=Bagnulo |first32=Stefano |last33=Bannister |first33=Michele T. |last34=Cambioni |first34=Saverio |last35=Bagatin |first35=Adriano Campo |last36=Chabot |first36=Nancy L. |last37=Cremonese |first37=Gabriele |last38=Daly |first38=R. Terik |last39=Dotto |first39=Elisabetta |last40=Glenar |first40=David A. |last41=Granvik |first41=Mikael |last42=Hasselmann |first42=Pedro H. |last43=Herreros |first43=Isabel |last44=Jacobson |first44=Seth |last45=Jutzi |first45=Martin |last46=Kohout |first46=Tomas |last47=La Forgia |first47=Fiorangela |last48=Lazzarin |first48=Monica |last49=Lin |first49=Zhong-Yi |last50=Lolachi |first50=Ramin |last51=Lucchetti |first51=Alice |last52=Makadia |first52=Rahil |last53=Epifani |first53=Elena Mazzotta |last54=Michel |first54=Patrick |last55=Migliorini |first55=Alessandra |last56=Moskovitz |first56=Nicholas A. |last57=Ormö |first57=Jens |last58=Pajola |first58=Maurizio |last59=Sánchez |first59=Paul |last60=Schwartz |first60=Stephen R. |last61=Snodgrass |first61=Colin |last62=Steckloff |first62=Jordan |last63=Stubbs |first63=Timothy J. |last64=Trigo-Rodríguez |first64=Josep M. |title=Ejecta from the DART-produced active asteroid Dimorphos |journal=Nature |date=1 March 2023 |volume=616 |issue=7957 |pages=452–456 |doi=10.1038/s41586-023-05811-4 |pmid=36858074 |pmc=10115637 |arxiv=2303.01700 |bibcode=2023Natur.616..452L |s2cid=257282549 |language=en |issn=1476-4687 |display-authors=3}}</ref> Observations show that Dimorphos lost approximately 1 million kilograms after the collision.<ref>{{cite journal |last1=Witze |first1=Alexandra |title=Asteroid lost 1 million kilograms after collision with DART spacecraft |journal=Nature |date=1 March 2023 |volume=615 |issue=7951 |pages=195 |doi=10.1038/d41586-023-00601-4 |pmid=36859675 |bibcode=2023Natur.615..195W |s2cid=257282080 |url=https://www.nature.com/articles/d41586-023-00601-4 |access-date=9 March 2023 |language=en|url-access=subscription }}</ref> Impact produced a dust plume that temporarily brightened the Didymos system and developed a {{convert|10000|km|mi|adj=on|sp=us}}-long [[comet tail|dust tail]] that persisted for several months.<ref name="NOIRLab-20221003">{{cite web
 |title = SOAR Telescope Catches Dimorphos's Expanding Comet-like Tail After DART Impact
 |url = https://noirlab.edu/public/news/noirlab2223/
 |first = Charles |last= Blue
 |publisher = NOIRLab
 |date = 3 October 2022
 |accessdate = 4 February 2023}}</ref><ref name="NASA-20221215">{{cite web
 |title = Early Results from NASA's DART Mission
 |url = https://www.nasa.gov/feature/early-results-from-nasa-s-dart-mission
 |first = Jessica |last= Merzdorf
 |publisher = NASA
 |date = 15 December 2022
 |accessdate = 4 February 2023}}</ref><ref name="Li2023">{{cite journal
  |display-authors = etal
  |first1 = Jian-Yang |last1 = Li
  |first2 = Masatoshi |last2 = Hirabayashi
  |first3 = Tony |last3 = Farnham
  |first4 = Matthew |last4 = Knight
  |first5 = Gonzalo |last5 = Tancredi
  |first6 = Fernando |last6 = Moreno
  |title = Ejecta from the DART-produced active asteroid Dimorphos
  |url = https://assets.researchsquare.com/files/rs-2292349/v1/34562254-db7b-4289-a7ff-238159687528.pdf?c=1669139626 <!-- Alternate url: https://www.nature.com/articles/s41586-023-05811-4.epdf?sharing_token=3oAIDKUcM5Ds3gutXzC3R9RgN0jAjWel9jnR3ZoTv0OAe1AwvJb0OMYms3u0qQ34fCbKw2XSq28hMy5oyRwGb2tMgzkHCczDVuFwylBsT_tSy24u64SAUKnD7M3U_zSK9qvfBxw4ZeTj_j73kCpFbRlzSeyKLLnDsgIvo97fnTtfRXcP9fKAfErZCPLOUlISKW7ytO8kM8h-rNimTAuxsVlg-VzM4zSHIqRSTwcDJqchEHtwmtrwbH8SlVAXAFrMePi74wqhUe-6MQ0eerqqDA%3D%3D&tracking_referrer=www.space.com -->
  |journal = Nature
  |date = March 2022
  |volume = 616 |issue = 7957 |pages = 452–456 |doi = 10.1038/s41586-023-05811-4
  |pmid = 36858074 |pmc = 10115637 |arxiv = 2303.01700
  |bibcode = 2023Natur.616..452L|s2cid = 257282549 }}</ref> The DART impact is predicted to have caused global resurfacing and deformation of Dimorphos's shape, leaving an [[impact crater]] several tens of meters in diameter.<ref name="Raducan2022">{{cite journal
  |first1 = Sabina D. |last1 = Raducan
  |first2 = Jutzi |last2 = Martin
  |title = Global-scale Reshaping and Resurfacing of Asteroids by Small-scale Impacts, with Applications to the DART and Hera Missions
  |journal = The Planetary Science Journal
  |date = July 2022
  |volume = 3
  |issue = 6
  |id = 128
  |pages = 15
  |doi-access = free
  |doi = 10.3847/PSJ/ac67a7
  |bibcode = 2022PSJ.....3..128R
  |s2cid = 249268810}}</ref><ref name="Nakano2022">{{cite journal
  |display-authors = etal
  |first1 = Ryota |last1 = Nakano
  |first2 = Masatoshi |last2 = Hirabayashi
  |first3 = M. |last3 = Brozovic
  |first4 = M. C. |last4 = Nolan
  |first5 = S. J. |last5 = Ostro
  |first6 = J. L. |last6 = Margot
  |title = NASA's Double Asteroid Redirection Test (DART): Mutual Orbital Period Change Due to Reshaping in the Near-Earth Binary Asteroid System (65803) Didymos
  |journal = The Planetary Science Journal
  |date = July 2022
  |volume = 3
  |issue = 7
  |id = 148
  |pages = 16
  |doi-access = free
  |doi = 10.3847/PSJ/ac7566
  |bibcode = 2022PSJ.....3..148N
  |s2cid = 250327233|hdl = 11311/1223308
  |hdl-access = free
  }}</ref><ref name="Raducan2023">{{cite conference
  |display-authors = etal
  |first1 = S. D. |last1 = Raducan
  |first2 = M. |last2 = Jutzi
  |first3 = Y. |last3 = Zhang
  |first4 = A. F. |last4 = Cheng
  |first5 = G. S. |last5 = Collins
  |first6 = T. M. |last6 = Davison
  |title =Low Strength of Asteroid Dimorphos As Demonstrated by the Dart Impact
  |url = https://www.hou.usra.edu/meetings/lpsc2023/pdf/2033.pdf
  |conference = 54th Lunar and Planetary Science Conference 2023
  |publisher = Lunar and Planetary Institute
  |date = March 2023 <!-- posted in Feb 2023 before scheduled presentation in Mar 2023 -->
  |issue = 2033
  |accessdate = 4 February 2023}}</ref> The impact has likely sent Dimorphos into a [[chaotic rotation|chaotically]] [[Precession|tumbling]] rotation that will subject the moon to irregular [[tidal force]]s by Didymos before it will eventually return to a [[tidal locking|tidally locked]] state within several decades.<ref name="Agrusa2021">{{cite journal
  |display-authors = etal
  |first1 = Harrison F. |last1 = Agrusa
  |first2 = Ioannis |last2 = Gkolias
  |first3 = Kleomenis |last3 = Tsiganis
  |first4 = Derek C. |last4 = Richardson
  |first5 = Alex J. |last5 = Meyer
  |first6 = Daniel J. |last6 = Scheeres
  |title = The excited spin state of Dimorphos resulting from the DART impact
  |journal = Icarus
  |date = December 2021
  |volume = 370
  |id = 114624
  |pages = 39
  |doi = 10.1016/j.icarus.2021.114624 
  |arxiv = 2107.07996
  |bibcode = 2021Icar..37014624A
  |s2cid = 236033921}}</ref><ref name="Richardson2022">{{cite journal
  |display-authors = etal
  |first1 = Derek C. |last1 = Richardson
  |first2 = Harrison F. |last2 = Agrusa
  |first3 = Brent |last3 = Barbee
  |first4 = William F.|last4 = Bottke
  |first5 = Andrew F. |last5 = Cheng
  |first6 = Siegfried |last6 = Eggl
  |title = Predictions for the Dynamical States of the Didymos System before and after the Planned DART Impact
  |journal = The Planetary Science Journal
  |date = July 2022
  |volume = 3
  |issue = 7
  |id = 157
  |pages = 23
  |doi-access = free
  |doi = 10.3847/PSJ/ac76c9 
  |arxiv = 2207.06998
  |bibcode = 2022PSJ.....3..157R
  |s2cid = 249268465}}</ref><ref name="Meyer2023">{{cite conference
  |display-authors = etal
  |first1 = A. J. |last1 = Meyer
  |first2 = G. |last2 = Noiset
  |first3 = Ö. |last3 = Karatekin
  |first4 = J. |last4 = McMahon
  |first5 = H. F. |last5 = Agrusa
  |first6 = R. |last6 = Nakano
  |title = Tidal Dissipation in Didymos Following the DART Impact
  |url = https://www.hou.usra.edu/meetings/lpsc2023/pdf/2105.pdf
  |conference = 54th Lunar and Planetary Science Conference 2023
  |publisher = Lunar and Planetary Institute
  |date = March 2023 <!-- posted in Feb 2023 before scheduled presentation in Mar 2023 -->
  |issue = 2105
  |accessdate = 4 February 2023}}</ref>

== Composition ==
Some active asteroids show signs that they are icy in composition like a traditional comet, while others are known to be rocky like an asteroid. It 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.<ref name="spacedaily">''[http://www.spacedaily.com/reports/Main_Belt_Comets_May_Have_Been_Source_Of_Earths_Water.html Main-Belt Comets May Have Been Source Of Earths Water]'', Space Daily, Mar 23, (2006).</ref> European scientists have proposed a sample-return mission from a MBC called ''Caroline'' to analyse the content of volatiles and collect dust samples.<ref name=Caroline />

== List ==
Identified members of this morphology class ([[Tisserand's parameter|T<sub>Jup</sub>]]>3.08) include:<ref name="Jewitt2022">{{cite book |editor-first1=K.|editor-last1=Meech|editor-first2=M.|editor-last2=Combi|chapter=The Asteroid-Comet Continuum|first1=David|last1=Jewitt|first2=Henry|last2=Hsieh|year=2022|title=Comets III|pages=34|publisher=University of Arizona Press|arxiv=2203.01397|bibcode=2022arXiv220301397J}}</ref>{{rp|page=17}}
{| border="1" class="wikitable sortable"
|-
! Name
! [[Semi-major axis]]<br/>([[astronomical unit|AU]])
! [[Perihelion]]<br/>(AU)
! [[Orbital eccentricity|Eccentricity]]
! [[Tisserand's parameter|T<sub>Jup</sub>]]
! Orbital<br/>class
! Diameter<br/>(km)
! [[Rotation period|Rotation<br/>period]] (hr)
! Cause
! Activity<br/>discovery<br/> year
! Recurrent?
|-
| [[Ceres (dwarf planet)|1 Ceres]]
| 2.766
| 2.550
| 0.078
| 3.310
| main-belt (middle)
| 939.4
| 9.07
| Water sublimation<ref name="JHA15">{{cite book|chapter=The Active Asteroids|first1=David|last1=Jewitt|first2=Henry|last2=Hsieh|first3=Jessica|last3=Agarwal|year=2015|title= Asteroids IV|pages=221–241| editor1-last =  Michel| editor1-first = P. | editor2-last = others| display-editors = 1 | publisher=[[University of Arizona]]|doi= 10.2458/azu_uapress_9780816532131-ch012 |arxiv=1502.02361|bibcode=2015aste.book..221J|isbn=9780816532131|s2cid=119209764| chapter-url= http://www2.ess.ucla.edu/~jewitt/papers/2015/JHA15.pdf |access-date=2020-01-30}}</ref>
| 2014
| 
|-
| [[493 Griseldis]]
| 3.116
| 2.568
| 0.176
| 3.140
| main-belt (outer)
| 41.56
| 51.94
| Impact<ref>{{Cite journal|last1=Tholen|first1=David J.|last2=Sheppard|first2=Scott S.|last3=Trujillo|first3=Chad A.|date=November 2015|title=Evidence for an Impact Event on (493) Griseldis|journal=DPS|volume=47|language=en|pages=414.03|bibcode=2015DPS....4741403T}}</ref>
| 2015
| {{N&}}
|-
| [[596 Scheila]]
| 2.929
| 2.45
| 0.163
| 3.209
| main-belt (outer)
| 159.72
| 15.85
| Impact<ref>{{Cite journal|last1=Bodewits|first1=D.|last2=Kelley|first2=M. S.|last3=Li|first3=J.-Y.|last4=Landsman|first4=W. B.|last5=Besse|first5=S.|last6=A’Hearn|first6=M. F.|title=Collisional Excavation of Asteroid (596) Scheila|date=2011-05-20|journal=The Astrophysical Journal|volume=733|issue=1|pages=L3|doi=10.1088/2041-8205/733/1/L3|issn=2041-8205|arxiv=1104.5227|bibcode=2011ApJ...733L...3B |s2cid=54187826}}</ref><ref>{{Cite journal|last1=Yang|first1=Bin|last2=Hsieh|first2=Henry|title=Near-Infrared Observations of Comet-Like Asteroid (596) Scheila|date=2011-08-20|journal=The Astrophysical Journal|volume=737|issue=2|pages=L39|doi=10.1088/2041-8205/737/2/L39|arxiv=1107.3845 |bibcode=2011ApJ...737L..39Y |issn=2041-8205|doi-access=free}}</ref><ref>{{Cite journal|last1=Hsieh|first1=Henry H.|last2=Yang|first2=Bin|last3=Haghighipour|first3=Nader|title=Optical and Dynamical Characterization of Comet-Like Main-Belt Asteroid (596) Scheila|date=2012-01-01|journal=The Astrophysical Journal|volume=744|issue=1|pages=9|doi=10.1088/0004-637X/744/1/9|arxiv=1109.3477|bibcode=2012ApJ...744....9H |s2cid=15039916|issn=0004-637X}}</ref>
| 2011
| {{N&}}
|-
| [[2201 Oljato]]
| 2.174
| 0.624
| 0.713
| 3.299
| NEO (Apollo)
| 1.8
| >26
| Sublimation<ref>{{Cite journal|last1=Russell|first1=C. T.|last2=Aroian|first2=R.|last3=Arghavani|first3=M.|last4=Nock|first4=K.|date=1984-10-05|title=Interplanetary Magnetic Field Enhancements and Their Association with the Asteroid 2201 Oljato|journal=Science|language=en|volume=226|issue=4670|pages=43–45|doi=10.1126/science.226.4670.43|pmid=17815417|bibcode=1984Sci...226...43R |s2cid=10618035|issn=0036-8075}}</ref>
| 1984
| {{N&}}
|-
| [[3200 Phaethon]]
| 1.271
| 0.140
| 0.890
| 4.510
| NEO (Apollo)
| 6.26
| 3.60
| Thermal fracturing, [[mudcrack|dehydration cracking]], and/or rotational disintegration<ref name=dusttail>{{Cite journal|last1=Jewitt|first1=David |first2=Jing|last2=Li |first3=Jessica|last3=Agarwal |title=The Dust Tail of Asteroid (3200) Phaethon|journal=The Astrophysical Journal |volume=771 |issue=2 |pages=L36 |arxiv=1306.3741|date=17 June 2013|doi=10.1088/2041-8205/771/2/L36 |bibcode = 2013ApJ...771L..36J |s2cid=37387069 }}</ref>
| 2010
| {{Y&}}
|-
| [[6478 Gault]]
| 2.305
| 1.860
| 0.193
| 3.461
| main-belt (inner)
| 5.6
| 2.49
| Rotational disintegration<ref>{{Cite journal|last1=Kleyna|first1=Jan T.|last2=Hainaut|first2=Olivier R.|last3=Meech|first3=Karen J.|last4=Hsieh|first4=Henry H.|last5=Fitzsimmons|first5=Alan|last6=Micheli|first6=Marco|last7=Keane|first7=Jacqueline V.|last8=Denneau|first8=Larry|last9=Tonry|first9=John|last10=Heinze|first10=Aren|last11=Bhatt|first11=Bhuwan C.|date=2019-04-01|title=The Sporadic Activity of (6478) Gault: A YORP-driven Event?|journal=The Astrophysical Journal|volume=874|issue=2|pages=L20|doi=10.3847/2041-8213/ab0f40| arxiv=1903.12142 |bibcode=2019ApJ...874L..20K |s2cid=85544222|issn=2041-8213|url=https://pureadmin.qub.ac.uk/ws/files/167036345/Kleyna_2019_ApJL_874_L20.pdf |doi-access=free }}</ref><ref>{{Cite journal|last1=Sanchez|first1=Juan A.|last2=Reddy|first2=Vishnu|last3=Thirouin|first3=Audrey|last4=Wright|first4=Edward L.|last5=Linder|first5=Tyler R.|last6=Kareta|first6=Theodore|last7=Sharkey|first7=Benjamin|date=2019-08-05|title=Physical Characterization of Active Asteroid (6478) Gault|journal=The Astrophysical Journal|volume=881|issue=1|pages=L6|doi=10.3847/2041-8213/ab31ac|arxiv=1907.06643|bibcode=2019ApJ...881L...6S |hdl=10150/634151|s2cid=196831757|issn=2041-8213|hdl-access=free |doi-access=free }}</ref><ref>{{Cite journal|last1=Chandler|first1=Colin Orion|last2=Kueny|first2=Jay|last3=Gustafsson|first3=Annika|last4=Trujillo|first4=Chadwick A.|last5=Robinson|first5=Tyler D.|last6=Trilling|first6=David E.|date=2019-05-22|title=Six Years of Sustained Activity in (6478) Gault|journal=The Astrophysical Journal|volume=877|issue=1|pages=L12|doi=10.3847/2041-8213/ab1aaa|bibcode=2019ApJ...877L..12C |issn=2041-8213|doi-access=free}}</ref>
| 2019
| {{Y&}}
|-
| {{hs|62412}}{{mp|(62412) 2000 SY|178}}
| 3.159
| 2.909
| 0.079
| 3.197
| main-belt (outer)
| 10.38
| 3.33
| Rotational disintegration<ref>{{Cite journal|last1=Sheppard|first1=Scott S.|last2=Trujillo|first2=Chadwick|title=Discovery and Characteristics of the Rapidly Rotating Active Asteroid (62412) 2000 SY178 in the Main Belt|date=2015-01-08|journal=The Astronomical Journal|volume=149|issue=2|pages=44|doi=10.1088/0004-6256/149/2/44|arxiv=1410.1528|bibcode=2015AJ....149...44S |s2cid=56464879|issn=1538-3881}}</ref>
| 2014
| {{N&}}
|-
| {{hs|65803}}[[65803 Didymos]]/[[Dimorphos]]
| 1.643
| 1.013
| 0.383
| 4.204
| NEO (Apollo)
| 0.77 / 0.15
| 2.26
| [[Double Asteroid Redirection Test|Human-caused impact]]
| 2022
| {{N&}}
|-
| {{hs|101955}}[[101955 Bennu]]
| 1.126
| 0.896
| 0.204
| 5.525
| NEO (Apollo)
| 0.48
| 4.29
| (unknown)<ref name="Jewitt2022"/>{{rp|page=22}}<br/>Electrostatic lofting, impacts, thermal fracturing, or dehydration cracking
| 2019
| {{Y&}}
|-
| {{hs|588045}}{{mp|(588045) 2007 FZ|18}}
| 3.176
| 2.783
| 0.124
| 3.188
| main-belt (outer)
| 
| 
| 
| 2023
| 
|-
| {{mp|2002 CW|116}}
| 2.690
| 2.068
| 0.231
| 3.319
| main-belt (middle)
| 0.5
|
|
| 2024
|
|-
| {{mp|2008 BJ|22}}
| 3.071
| 2.943
| 0.042
| 3.199
| main-belt (outer)
| <0.4
| 
| 
| 2022
| {{N&}}
|-
| {{mp|2010 LH|15}}
| 2.744
| 1.770
| 0.355
| 3.230
| main-belt (middle)
| 1.483
| 
| 
| 2023
| {{Y&}}
|-
| {{mp|2015 BC|566}}
| 3.062
| 2.957
| 0.034
| 3.201
| main-belt (outer)
| 
|
|
| 2023
| {{N&}}
|-
| {{mp|2015 FW|412}}
| 2.765
| 2.319
| 0.161
| 3.280
| main-belt (middle)
| 
| 
| 
| 2023
| 
|-
| {{mp|2015 VA|108}}
| 3.128
| 2.451
| 0.217
| 3.160
| main-belt (outer)
| 
| 
| 
| 2023
|
|-
| {{mp|2023 JN|16}}
| 2.696
| 2.300
| 0.147
| 3.351
| main-belt (middle)
| 
| 
| 
| 2023
|
|-
| {{hs|C}}[[4015 Wilson–Harrington|107P/4015 Wilson–Harrington]]
| 2.625
| 0.966
| 0.632
| 3.082
| NEO (Apollo)
| 6.92
| 7.15
| Sublimation<ref>{{Cite journal|last1=Ferrín|first1=Ignacio|last2=Hamanowa|first2=Hiromi|last3=Hamanowa|first3=Hiroko|last4=Hernández|first4=Jesús|last5=Sira|first5=Eloy|last6=Sánchez|first6=Albert|last7=Zhao|first7=Haibin|last8=Miles|first8=Richard|date=September 2012|title=The 2009 Apparition of methuselah comet 107P/Wilson–Harrington: A case of comet rejuvenation?|journal=Planetary and Space Science|language=en|volume=70|issue=1|pages=59–72|doi=10.1016/j.pss.2012.05.022|arxiv=1205.6874|bibcode=2012P&SS...70...59F |s2cid=118530975}}</ref><ref>{{Cite journal|last1=Fernández|first1=Yanga R.|last2=McFadden|first2=Lucy A.|last3=Lisse|first3=Carey M.|last4=Helin|first4=Eleanor F.|last5=Chamberlin|first5=Alan B.|date=July 1997|title=Analysis of POSS Images of Comet–Asteroid Transition Object 107P/1949 W1 (Wilson–Harrington)|journal=Icarus|language=en|volume=128|issue=1|pages=114–126|doi=10.1006/icar.1997.5728|bibcode=1997Icar..128..114F }}</ref>
| 1949
| {{N&}}
|-
| {{hs|C}}[[7968 Elst–Pizarro|133P/7968 Elst–Pizarro]]
| 3.165
| 2.668
| 0.157
| 3.184
| main-belt (outer)
| 3.8
| 3.47
| Sublimation/rotational disintegration<ref>{{Cite journal|last1=Hsieh|first1=Henry H.|last2=Jewitt|first2=David C.|last3=Fernández|first3=Yanga R.|date=May 2004|title=The Strange Case of 133P/Elst-Pizarro: A Comet among the Asteroids|journal=The Astronomical Journal|language=en|volume=127|issue=5|pages=2997–3017|doi=10.1086/383208|bibcode=2004AJ....127.2997H |issn=0004-6256|doi-access=free}}</ref><ref>{{Cite journal|last1=Jewitt|first1=David|last2=Ishiguro|first2=Masateru|last3=Weaver|first3=Harold|last4=Agarwal|first4=Jessica|last5=Mutchler|first5=Max|last6=Larson|first6=Steven|title=Hubble Space Telescopeinvestigation of Main-Belt Comet 133P/Elst-Pizarro|date=2014-04-11|journal=The Astronomical Journal|volume=147|issue=5|pages=117|doi=10.1088/0004-6256/147/5/117|arxiv=1402.5571 |bibcode=2014AJ....147..117J |issn=0004-6256|doi-access=free}}</ref>
| 1996
| {{Y&}}
|-
| {{hs|C}}[[118401 LINEAR|176P/118401 LINEAR]]
| 3.194
| 2.578
| 0.193
| 3.167
| main-belt (outer)
| 4.0
| 22.23
| Sublimation<ref>{{Cite journal|last1=Hsieh|first1=Henry H.|last2=Denneau|first2=Larry|last3=Fitzsimmons|first3=Alan|last4=Hainaut|first4=Olivier R.|last5=Ishiguro|first5=Masateru|last6=Jedicke|first6=Robert|last7=Kaluna|first7=Heather M.|last8=Keane|first8=Jacqueline V.|last9=Kleyna|first9=Jan|last10=Lacerda|first10=Pedro|last11=MacLennan|first11=Eric M.|title=Search for the Return of Activity in Active Asteroid 176P/Linear|date=2014-03-14|journal=The Astronomical Journal|volume=147|issue=4|pages=89|doi=10.1088/0004-6256/147/4/89|arxiv=1408.4865 |bibcode=2014AJ....147...89H |issn=0004-6256|doi-access=free}}</ref>
| 2005
| {{N&}}
|-
| {{hs|C}}[[233P/La Sagra]] ({{mp|P/2009 WJ|50}})
| 3.033
| 1.786
| 0.411
| 3.081
| main-belt (outer)
| 3.0
| 
| 
| 2010
| {{N&}}
|-
| {{hs|C}}[[238P/Read]] (P/2005 U1)
| 3.162
| 2.362
| 0.253
| 3.153
| main-belt (outer)
| 0.8
| 
| Sublimation<ref>{{Cite journal|last1=Hsieh|first1=Henry H.|last2=Meech|first2=Karen J.|last3=Pittichová|first3=Jana|title=Main-Belt Comet 238P/Read Revisited|date=2011-07-20|journal=The Astrophysical Journal|volume=736|issue=1|pages=L18|doi=10.1088/2041-8205/736/1/L18|arxiv=1106.0045 |bibcode=2011ApJ...736L..18H |issn=2041-8205|doi-access=free}}</ref>
| 2005
| {{Y&}}
|-
| {{hs|C}}[[259P/Garradd]] (P/2008 R1)
| 2.727
| 1.794
| 0.342
| 3.217
| main-belt (middle)
| 0.60
| 
| Sublimation<ref>{{Cite journal|last1=Jewitt|first1=David|last2=Yang|first2=Bin|last3=Haghighipour|first3=Nader|title=Main-Belt Comet P/2008 R1 (Garradd)|date=2009-05-01|journal=The Astronomical Journal|volume=137|issue=5|pages=4313–4321|doi=10.1088/0004-6256/137/5/4313|arxiv=0902.4315 |bibcode=2009AJ....137.4313J |issn=0004-6256|doi-access=free}}</ref>
| 2008
| {{Y&}}
|-
| {{hs|C}}[[(300163) 2006 VW139|288P/{{mp|(300163) 2006 VW|139}}]]
| 3.051
| 2.438
| 0.201
| 3.203
| main-belt (outer)
| 1.8 / 1.2
| 
| Sublimation<ref>{{Cite journal|last1=Agarwal|first1=Jessica|last2=Jewitt|first2=David|last3=Mutchler|first3=Max|last4=Weaver|first4=Harold|last5=Larson|first5=Stephen|date=September 2017|title=A binary main-belt comet|journal=Nature|language=en|volume=549|issue=7672|pages=357–359|doi=10.1038/nature23892|pmid=28933430|arxiv=1710.03454|bibcode=2017Natur.549..357A |s2cid=4469577|issn=0028-0836}}</ref>
| 2011
| {{Y&}}
|-
| {{hs|C}}[[311P/PanSTARRS]] (P/2013 P5)
| 2.189
| 1.935
| 0.116
| 3.660
| main-belt (inner)
| 0.4
| >5.4
| Rotational disintegration<ref>{{Cite journal|last1=Jewitt|first1=David|last2=Agarwal|first2=Jessica|last3=Weaver|first3=Harold|last4=Mutchler|first4=Max|last5=Larson|first5=Stephen|title=The Extraordinary Multi-Tailed Main-Belt Comet P/2013 P5|date=2013-11-07|journal=The Astrophysical Journal|volume=778|issue=1|pages=L21|doi=10.1088/2041-8205/778/1/L21|arxiv=1311.1483 |bibcode=2013ApJ...778L..21J |issn=2041-8205|doi-access=free}}</ref><ref>{{Cite journal|last1=Moreno|first1=F.|last2=Licandro|first2=J.|last3=Álvarez-Iglesias|first3=C.|last4=Cabrera-Lavers|first4=A.|last5=Pozuelos|first5=F.|title=Intermittent Dust Mass Loss from Activated Asteroid P/2013 P5 (Panstarrs)|date=2014-01-16|journal=The Astrophysical Journal|volume=781|issue=2|pages=118|doi=10.1088/0004-637X/781/2/118|issn=0004-637X|arxiv=1312.5895|bibcode=2014ApJ...781..118M |s2cid=119298012}}</ref><ref>{{Cite journal|last1=Hainaut|first1=O. R.|last2=Boehnhardt|first2=H.|last3=Snodgrass|first3=C.|last4=Meech|first4=K. J.|last5=Deller|first5=J.|last6=Gillon|first6=M.|last7=Jehin|first7=E.|last8=Kuehrt|first8=E.|last9=Lowry|first9=S. C.|last10=Manfroid|first10=J.|last11=Micheli|first11=M.|date=March 2014|title=Continued activity in P/2013 P5 PANSTARRS: Unexpected comet, rotational disintegration, or rubbing binary asteroid?|journal=Astronomy & Astrophysics|volume=563|pages=A75|doi=10.1051/0004-6361/201322864|issn=0004-6361|doi-access=free}}</ref>
| 2013
| {{Y&}}
|-
| {{hs|C}}[[313P/Gibbs]] (P/2003 S10)
| 3.154
| 2.391
| 0.242
| 3.133
| main-belt (outer)
| 2.0
| 
| Sublimation<ref>{{Cite journal|last1=Hui|first1=Man-To|last2=Jewitt|first2=David|title=Archival Observations of Active Asteroid 313P/Gibbs|date=2015-03-16|journal=The Astronomical Journal|volume=149|issue=4|pages=134|doi=10.1088/0004-6256/149/4/134|bibcode=2015AJ....149..134H |s2cid=44820411 |issn=1538-3881}}</ref>
| 2003
| {{Y&}}
|-
| {{hs|C}}[[324P/La Sagra]] (P/2010 R2)
| 3.098
| 2.621
| 0.154
| 3.099
| main-belt (outer)
| 1.1
|
| Sublimation<ref>{{Cite journal|last1=Jewitt|first1=David|last2=Agarwal|first2=Jessica|last3=Weaver|first3=Harold|last4=Mutchler|first4=Max|last5=Li|first5=Jing|last6=Larson|first6=Stephen|date=2016-09-06|title=HUBBLE SPACE TELESCOPE OBSERVATIONS OF ACTIVE ASTEROID 324P/La SAGRA|journal=The Astronomical Journal|volume=152|issue=3|pages=77|doi=10.3847/0004-6256/152/3/77|arxiv=1606.08522 |bibcode=2016AJ....152...77J |hdl=10150/621499|s2cid=119293534|issn=1538-3881|hdl-access=free |doi-access=free }}</ref>
| 2010
| {{Y&}}
|-
| {{hs|C}}[[331P/Gibbs]] (P/2012 F5)
| 3.005
| 2.879
| 0.042
| 3.228
| main-belt (outer)
| 3.54
| 3.24
| Rotational disintegration<ref>{{Cite journal|last1=Stevenson|first1=R.|last2=Kramer|first2=E. A.|last3=Bauer|first3=J. M.|last4=Masiero|first4=J. R.|last5=Mainzer|first5=A. K.|title=Characterization of Active Main Belt Object P/2012 F5 (Gibbs): A Possible Impacted Asteroid|date=2012-11-10|journal=The Astrophysical Journal|volume=759|issue=2|pages=142|doi=10.1088/0004-637X/759/2/142|arxiv=1209.5450 |bibcode=2012ApJ...759..142S |issn=0004-637X|doi-access=free}}</ref><ref>{{Cite journal|last1=Drahus|first1=Michał|last2=Waniak|first2=Wacław|last3=Tendulkar|first3=Shriharsh|last4=Agarwal|first4=Jessica|last5=Jewitt|first5=David|last6=Sheppard|first6=Scott S.|title=Fast Rotation and Trailing Fragments of the Active Asteroid P/2012 F5 (Gibbs)|date=2015-03-20|journal=The Astrophysical Journal|volume=802|issue=1|pages=L8|doi=10.1088/2041-8205/802/1/L8|arxiv=1503.05632 |bibcode=2015ApJ...802L...8D |issn=2041-8213|doi-access=free}}</ref>
| 2012
| {{N&}}
|-
| {{hs|C}}[[354P/LINEAR]] (P/2010 A2)
| 2.290
| 2.004
| 0.125
| 3.583
| main-belt (inner)
| 0.12
| 11.36
| Impact<ref>{{Cite journal|last1=Jewitt|first1=David|last2=Ishiguro|first2=Masateru|last3=Agarwal|first3=Jessica|title=Large Particles in Active Asteroid P/2010 A2|date=2013-01-24|journal=The Astrophysical Journal|volume=764|issue=1|pages=L5|doi=10.1088/2041-8205/764/1/L5|issn=2041-8205|arxiv=1301.2566|bibcode=2013ApJ...764L...5J |s2cid=37325835}}</ref>
| 2010
| {{N&}}
|-
| {{hs|C}}358P/PanSTARRS (P/2012 T1)
| 3.155
| 2.410
| 0.236
| 3.134
| main-belt (outer)
| 0.64
| 
| Sublimation<ref>{{Cite journal|last1=Hsieh|first1=Henry H.|last2=Kaluna|first2=Heather M.|last3=Novaković|first3=Bojan|last4=Yang|first4=Bin|last5=Haghighipour|first5=Nader|last6=Micheli|first6=Marco|last7=Denneau|first7=Larry|last8=Fitzsimmons|first8=Alan|last9=Jedicke|first9=Robert|last10=Kleyna|first10=Jan|last11=Vereš|first11=Peter|title=Main-Belt Comet P/2012 T1 (Panstarrs)|date=2013-06-11|journal=The Astrophysical Journal|volume=771|issue=1|pages=L1|doi=10.1088/2041-8205/771/1/L1|arxiv=1305.5558 |bibcode=2013ApJ...771L...1H |issn=2041-8205|hdl=1721.1/93906|s2cid=166874|hdl-access=free}}</ref>
| 2012
| {{N&}}
|-
| {{hs|C}}426P/PanSTARRS (P/2019 A7)
| 3.188
| 2.675
| 0.161
| 3.103
| main-belt (outer)
| 2.4
| 
| 
| 2019
| {{N&}}
|-
| {{hs|C}}427P/ATLAS (P/2017 S5)
| 3.171
| 2.178
| 0.313
| 3.092
| main-belt (outer)
| 0.90
| 1.4
| Sublimation/rotational disintegration<ref>{{cite journal|title=Active Asteroid P/2017 S5 (ATLAS)|first1=David|last1=Jewitt|last2=others|display-authors=1|journal=[[The Astronomical Journal]]|volume=157|pages=54|number=2|date= 18 January 2019|doi = 10.3847/1538-3881/aaf563|arxiv=1812.00060|bibcode=2019AJ....157...54J|s2cid=119508428 |doi-access=free }}</ref>
| 2017
| {{N&}}
|-
| {{hs|C}}432P/PanSTARRS (P/2021 N4)
| 3.045
| 2.302
| 0.244
| 3.170
| main-belt (outer)
| <1.4
|
| 
| 2021
| {{N&}}
|-
| {{hs|C}}[[(248370) 2005 QN173|433P/{{mp|(248370) 2005 QN|173}}]]
| 3.067
| 2.374
| 0.226
| 3.192
| main-belt (outer)
| 3.2
| 
| Sublimation/rotational disintegration
| 2021
| {{Y&}}
|-
| {{hs|C}}435P/PanSTARRS (P/2021 T3)
| 3.018
| 2.056
| 0.319
| 3.090
| main-belt (outer)
| 
| 
| 
| 2021
| {{N&}}
|-
| {{hs|C}}455P/PanSTARRS (P/2021 S9)
| 3.156
| 2.193
| 0.305
| 3.087
| main-belt (outer)
| <1.6
| 
| 
| 2017
| {{N&}}
|-
| {{hs|C}}456P/PanSTARRS (P/2021 L4)
| 3.165
| 2.788
| 0.119
| 3.125
| main-belt (outer)
| <4.4
| 
| 
| 2021
| {{N&}}
|-
| {{hs|C}}457P/2020 O1 (Lemmon–PanSTARRS)
| 2.647
| 2.329
| 0.120
| 3.376
| main-belt (middle)
| 0.84
| 1.67
| Sublimation/rotational disintegration<ref>{{cite journal|title=Hubble Space Telescope Observations of Active Asteroid P/2020 O1 (Lemmon-PANSTARRS)|first1=Yoonyoung|last1=Kim|first2=David|last2=Jewitt|first3=Jessica|last3=Agarwal|first4=Max|last4=Mutchler|first5=Jing|last5=Li|first6=Harold|last6=Weaver|journal=The Astrophysical Journal Letters|volume=933|issue=1|id=L15|pages=10|date=July 2022|doi=10.3847/2041-8213/ac78de|arxiv=2206.07703|bibcode=2022ApJ...933L..15K|s2cid=249674510 |doi-access=free }}</ref>
| 2020
| {{Y&}}
|-
| [[483P/PanSTARRS]] (P/2016 J1)
| 3.172
| 2.449
| 0.228
| 3.113
| main-belt (outer)
| <1.8 / <0.8
| 
| Sublimation<ref name=":1">{{Cite journal|last1=Hui (許文韜)|first1=Man-To|last2=Jewitt|first2=David|last3=Du (杜辛楠)|first3=Xinnan|date=2017-03-07|title=Split Active Asteroid P/2016 J1 (PANSTARRS)|journal=The Astronomical Journal|volume=153|issue=4|pages=141|doi=10.3847/1538-3881/aa6039|arxiv=1702.02766|bibcode=2017AJ....153..141H |s2cid=118824144|issn=1538-3881 |doi-access=free }}</ref>
| 2016
| {{Y&}}
|-
| [[P/2013 R3 (Catalina–PanSTARRS)]]
| 3.033
| 2.205
| 0.273
| 3.184
| main-belt (outer)
| ~0.4
| 
| Sublimation/rotational disintegration<ref name=":0">{{Cite journal|last1=Jewitt|first1=David|last2=Agarwal|first2=Jessica|last3=Li|first3=Jing|last4=Weaver|first4=Harold|last5=Mutchler|first5=Max|last6=Larson|first6=Stephen|title=Disintegrating Asteroid P/2013 R3|date=2014-03-06|journal=The Astrophysical Journal|volume=784|issue=1|pages=L8|doi=10.1088/2041-8205/784/1/L8|issn=2041-8205|arxiv=1403.1237|bibcode=2014ApJ...784L...8J |s2cid=54680553}}</ref>
| 2013
| {{N&}}
|-
| P/2015 X6 (PanSTARRS)
| 2.755
| 2.287
| 0.170
| 3.318
| main-belt (middle)
| <1.4
| 
| Sublimation<ref>{{Cite journal|last1=Moreno|first1=F.|last2=Licandro|first2=J.|last3=Cabrera-Lavers|first3=A.|last4=Pozuelos|first4=F. J.|title=Dust Loss from Activated Asteroid P/2015 X6|date=2016-07-27|journal=The Astrophysical Journal|volume=826|issue=2|pages=137|doi=10.3847/0004-637X/826/2/137|arxiv=1605.04802|bibcode=2016ApJ...826..137M |s2cid=118558049|issn=1538-4357 |doi-access=free }}</ref>
| 2015
| {{N&}}
|-
| [[P/2016 G1 (PanSTARRS)]]
| 2.583
| 2.041
| 0.210
| 3.367
| main-belt (middle)
| <0.8
| 
| Impact<ref>{{Cite journal|last1=Moreno|first1=F.|last2=Licandro|first2=J.|last3=Cabrera-Lavers|first3=A.|last4=Pozuelos|first4=F. J.|title=Early Evolution of Disrupted Asteroid P/2016 G1 (PANSTARRS)|date=2016-07-26|journal=The Astrophysical Journal|volume=826|issue=2|pages=L22|doi=10.3847/2041-8205/826/2/L22|arxiv=1607.03375 |bibcode=2016ApJ...826L..22M |issn=2041-8213|doi-access=free}}</ref>
| 2016
| {{N&}}
|-
| P/2018 P3 (PanSTARRS)
| 3.007
| 1.756
| 0.416
| 3.096
| main-belt (outer)
| <1.2
| 
| Sublimation
| 2018
| {{Y&}}
|-
| P/2019 A3 (PanSTARRS)
| 3.147
| 2.313
| 0.265
| 3.099
| main-belt (outer)
| <0.8
| 
| 
| 2019
| {{N&}}
|-
| P/2019 A4 (PanSTARRS)
| 2.614
| 2.379
| 0.090
| 3.365
| main-belt (middle)
| 0.34
| 
| 
| 2019
| {{N&}}
|-
| P/2021 A5 (PanSTARRS)
| 3.047
| 2.620
| 0.140
| 3.147
| main-belt (outer)
| 0.30
| 
| Sublimation
| 2021
| {{N&}}
|-
| P/2021 R8 (Sheppard)
| 3.019
| 2.131
| 0.294
| 3.179
| main-belt (outer)
|
|
| 
| 2021
| {{N&}}
|-
| P/2022 R5 (PanSTARRS)
| 3.071
| 2.470
| 0.196
| 3.148
| main-belt (outer)
| 
| 
| 
| 2022
| 
|-
| P/2023 S4 (Hogan)
| 3.134
| 2.542
| 0.189
| 3.185
| main-belt (outer)
| 
| 
| 
| 2023
| 
|-
| P/2024 L4 (Rankin)
| 2.231
| 0.672
| 0.699
| 3.255
| NEO (apollo)
| <0.4
|
| Rotational disintegration?
| 2024
|
|-
| P/2024 R2 (PANSTARRS)
| 3.138
| 2.302
| 0.266
| 3.104
| main-belt (outer)
| 
|
|
| 2024
|
|}

==Exploration==
[[File:PIA23554-AsteroidBennu-EjectingParticles-20190106.jpg|thumb|300px|Asteroid [[101955 Bennu]] seen ejecting particles on January 6, 2019, in images taken by the [[OSIRIS-REx]] spacecraft]]
[[Castalia (spacecraft)|''Castalia'']] 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.<ref name="Snodgrass 2018">{{cite journal|doi=10.1016/j.asr.2017.09.011|title=The Castalia mission to Main Belt Comet 133P/Elst-Pizarro|journal=Advances in Space Research|volume=62|issue=8|pages=1947–1976|year=2018|last1=Snodgrass|first1=C.|last2=Jones|first2=G.H.|last3=Boehnhardt|first3=H.|last4=Gibbings|first4=A.|last5=Homeister|first5=M.|last6=Andre|first6=N.|last7=Beck|first7=P.|last8=Bentley|first8=M.S.|last9=Bertini|first9=I.|last10=Bowles|first10=N.|last11=Capria|first11=M.T.|last12=Carr|first12=C.|last13=Ceriotti|first13=M.|last14=Coates|first14=A.J.|last15=Della Corte|first15=V.|last16=Donaldson Hanna|first16=K.L.|last17=Fitzsimmons|first17=A.|last18=Gutiérrez|first18=P.J.|last19=Hainaut|first19=O.R.|last20=Herique|first20=A.|last21=Hilchenbach|first21=M.|last22=Hsieh|first22=H.H.|last23=Jehin|first23=E.|last24=Karatekin|first24=O.|last25=Kofman|first25=W.|last26=Lara|first26=L.M.|last27=Laudan|first27=K.|last28=Licandro|first28=J.|last29=Lowry|first29=S.C.|last30=Marzari|first30=F.|display-authors=29|bibcode=2018AdSpR..62.1947S|arxiv=1709.03405|s2cid=55821241}}</ref> 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|Cosmic Vision programme]] missions M4 and M5, but it was not selected. The team continues to mature the mission concept and science objectives.<ref name="Snodgrass 2018"/> Because of the construction time required and orbital dynamics, a launch date of October 2028 was proposed.<ref name="Snodgrass 2018"/>

On January 6, 2019, the [[OSIRIS-REx]] mission first observed episodes of particle ejection from [[101955 Bennu]] shortly after entering orbit around the [[Near-Earth object|near-Earth asteroid]], leading it to be newly classified as an active asteroid and marking the first time that asteroid activity had been observed up close by a spacecraft. It has since observed at least 10 other such events.<ref name="NYT-20190319" /> The scale of these observed mass loss events is much smaller than those previously observed at other active asteroids by telescopes, indicating that there is a continuum of mass loss event magnitudes at active asteroids.<ref name="Science_3544">{{cite journal|title = Episodes of particle ejection from the surface of the active asteroid (101955) Bennu|first1 = D. S. | last1 = Lauretta| first2 = C. W. |last2 = Hergenrother | first3 = S. R. | last3 = Chesley | first4 = J. M. | last4 = Leonard | first5 = J. Y. | last5 = Pelgrift | first6 = C. D. | last6 = Adam | first7 = M. | last7 = Al Asad|display-authors=5|  journal    = Science | date = 6 Dec 2019| volume = 366 | issue = 6470 |pages = eaay3544 | doi = 10.1126/science.aay3544 |pmid = 31806784 |bibcode = 2019Sci...366.3544L |s2cid = 208764910 |url = http://oro.open.ac.uk/68479/1/Lauretta_et_al_2019_accepted.pdf | doi-access = free }}</ref>

== See also ==
*[[Centaur (minor planet)]] 
*[[Extinct comet]]

== References ==
{{reflist}}

== External links ==
* [http://asteroids.matf.bg.ac.rs/fam/properelements.php Proper elements of active asteroids at Asteroid Families Portal]
* Henry Hsieh's [https://web.archive.org/web/20111026205513/http://www.ifa.hawaii.edu/users/hsieh/mbcs.shtml Main-Belt Comets] page has extensive details on Main-belt comets
* [http://www2.ess.ucla.edu/~jewitt/mbc.html David Jewitt. The Active Asteroids]
* [https://web.archive.org/web/20070501211319/http://www.planetary.org/blog/article/00000551/ Planetary Society article on MBCs]
* [http://www.centauri-dreams.org/?p=601 Discussion of possible differences in characteristics of the water in MBCs and other comets]
* YouTube [https://www.youtube.com/watch?v=B1W4NTmI5Bk Interview with David Jewitt] (discussion on main-belt comets starts around 9 minutes into video)
* [http://www2.ess.ucla.edu/~jewitt/images/Impact_Trigger_sketch.jpg Impact trigger mechanism] diagram by [[David C. Jewitt|David Jewitt]]
* [http://remanzacco.blogspot.com/2010/12/comet-like-appearance-of-596-scheila.html Comet-like appearance of (596) Scheila]
* [https://web.archive.org/web/20110719023715/http://asteroidi.uai.it/t3.htm Project T3: Finding Comets in the Asteroid Population]
* {{cite journal |arxiv=1112.5220|doi=10.1088/0004-6256/143/3/66|bibcode=2012AJ....143...66J|title=The Active Asteroids|year=2012|last1=Jewitt|first1=David|journal=The Astronomical Journal|volume=143|issue=3|pages=66|s2cid=45208650}}
* {{cite journal |arxiv=1202.2126|doi=10.1088/2041-8205/748/1/L15|bibcode=2012ApJ...748L..15H|title=DISCOVERY OF MAIN-BELT COMET P/2006 VW 139 BY Pan-STARRS1|year=2012|last1=Hsieh|first1=Henry H.|last2=Yang|first2=Bin|last3=Haghighipour|first3=Nader|last4=Kaluna|first4=Heather M.|last5=Fitzsimmons|first5=Alan|last6=Denneau|first6=Larry|last7=Novaković|first7=Bojan|last8=Jedicke|first8=Robert|last9=Wainscoat|first9=Richard J.|last10=Armstrong|first10=James D.|last11=Duddy|first11=Samuel R.|last12=Lowry|first12=Stephen C.|last13=Trujillo|first13=Chadwick A.|last14=Micheli|first14=Marco|last15=Keane|first15=Jacqueline V.|last16=Urban|first16=Laurie|last17=Riesen|first17=Timm|last18=Meech|first18=Karen J.|last19=Abe|first19=Shinsuke|last20=Cheng|first20=Yu-Chi|last21=Chen|first21=Wen-Ping|last22=Granvik|first22=Mikael|last23=Grav|first23=Tommy|last24=Ip|first24=Wing-Huen|author-link24= Ip Wing-huen|last25=Kinoshita|first25=Daisuke|last26=Kleyna|first26=Jan|last27=Lacerda|first27=Pedro|last28=Lister|first28=Tim|last29=Milani|first29=Andrea|last30=Tholen|first30=David J.|journal=The Astrophysical Journal|volume=748|issue=1|pages=L15|s2cid=8693844|display-authors=29}}
* [http://remanzacco.blogspot.it/2012/10/new-comet-p2012-t1-panstarrs.html New Comet: P/2012 T1 (PANSTARRS)] (Remanzacco Observatory : 16 Oct 2012)
* {{cite journal |arxiv=1305.2621|doi=10.1093/mnras/stt839|bibcode=2013MNRAS.434.1821F|title=The location of Asteroidal Belt Comets (ABCs), in a comet's evolutionary diagram: The Lazarus Comets|year=2013|last1=Ferrín|first1=Ignacio|last2=Zuluaga|first2=Jorge|last3=Cuartas|first3=Pablo|journal=Monthly Notices of the Royal Astronomical Society|volume=434|issue=3|pages=1821–1837|doi-access=free |s2cid=118177774}}
* [http://www.iac.es/divulgacion.php?op1=16&id=816&lang=en P/2013 R3: a Main Belt Comet that is breaking apart. J. Licandro] New images obtained with the [[Gran Telescopio Canarias|GTC]]

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