Editing Comet (section)

== Fate of comets ==

=== Departure (ejection) from Solar System ===

If a comet is traveling fast enough, it may leave the Solar System. Such comets follow the open path of a hyperbola, and as such, they are called hyperbolic comets. Solar comets are only known to be ejected by [[Perturbation (astronomy)|interacting]] with another object in the Solar System, such as Jupiter.<ref>{{cite journal |bibcode=1991JBAA..101..119H |title=On hyperbolic comets |last1=Hughes |first1=D. W. |volume=101 |date=1991 |pages=119 |journal=Journal of the British Astronomical Association}}</ref> An example of this is Comet [[C/1980 E1]], which was shifted from an orbit of 7.1&nbsp;million years around the Sun, to a hyperbolic trajectory, after a 1980 close pass by the planet Jupiter.<ref name=barycenter>{{cite web |author=[[JPL Horizons On-Line Ephemeris System|Horizons]] output |url=http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=C/1980+E1 |title=Barycentric Osculating Orbital Elements for Comet C/1980 E1 |access-date=9 March 2011}} (Solution using the Solar System [[Center of mass#Barycenter in astrophysics and astronomy|Barycenter]] and [[Barycentric coordinates (astronomy)|barycentric coordinates]]. Select Ephemeris Type:Elements and Center:@0)</ref> Interstellar comets such as [['Oumuamua|1I/ʻOumuamua]] and [[2I/Borisov]] never orbited the Sun and therefore do not require a 3rd-body interaction to be ejected from the Solar System.

=== Extinction ===
{{Main|Extinct comet}}

Jupiter-family comets and long-period comets appear to follow very different fading laws. The JFCs are active over a lifetime of about 10,000 years or ~1,000 orbits whereas long-period comets fade much faster. Only 10% of the long-period comets survive more than 50 passages to small perihelion and only 1% of them survive more than 2,000 passages.<ref name=dormant/> Eventually most of the volatile material contained in a comet nucleus evaporates, and the comet becomes a small, dark, inert lump of rock or rubble that can resemble an asteroid.<ref>{{cite web |last=Lyzenga |first=Greg |title=If comets melt, why do they seem to last for long periods of time |url=http://www.scientificamerican.com/article.cfm?id=if-comets-melt-why-do-the |work=[[Scientific American]] |date=16 November 1998 |access-date=13 August 2013}}</ref> Some asteroids in elliptical orbits are now identified as extinct comets.<ref>{{cite journal |url=http://www.boulder.swri.edu/~hal/PDF/asteroids3.pdf |archive-url=https://web.archive.org/web/20040202155133/http://www.boulder.swri.edu/~hal/PDF/asteroids3.pdf |archive-date=2004-02-02 |url-status=live |title=Evolution of Comets into Asteroids |journal=Asteroids III |last1=Bottke |first1=William F. Jr. |last2=Levison |first2=Harold F. |name-list-style=amp |page=669 |date=2002 |bibcode=2002aste.book..669W}}</ref><ref>{{cite journal |title=Are the IRAS-detected Apollo asteroids extinct comets? |journal=Monthly Notices of the Royal Astronomical Society |first=J. K. |last=Davies |volume=221 |pages=19P–23P |date=July 1986 |doi=10.1093/mnras/221.1.19P |bibcode=1986MNRAS.221P..19D|doi-access=free }}</ref><ref>{{cite book |chapter=The Comet-Asteroid Transition: Recent Telescopic Observations |title=Asteroids, Comets, Meteors 1993: Proceedings of the 160th Symposium of the International Astronomical Union, Held in Belgirate, Italy, June 14–18, 1993 |volume=160 |publisher=Springer |first=L. A. |last=McFadden |editor1-first=Andrea |editor1-last=Milani |editor2-first=Michel |editor2-last=Di Martino |editor3-first=A. |editor3-last=Cellino |page=95 |date=1994 |bibcode=1994IAUS..160...95M}}</ref><ref>{{cite journal |title=The enigmatic object 2201 Oljato: Is it an asteroid or an evolved comet? |journal=Journal of Geophysical Research |first1=L. A. |last1=McFadden |first2=A. L. |last2=Cochran |first3=E. S. |last3=Barker |first4=D. P. |last4=Cruikshank |first5=W. K. |last5=Hartmann |display-authors=1 |volume=98 |issue=E2 |pages=3031–3041 |date=February 1993 |doi=10.1029/92JE01895 |bibcode=1993JGR....98.3031M}}</ref> Roughly six percent of the near-Earth asteroids are thought to be extinct comet nuclei.<ref name=dormant/>

=== Breakup and collisions ===

The nucleus of some comets may be fragile, a conclusion supported by the observation of comets splitting apart.<ref>{{cite news |url=http://news.bbc.co.uk/1/hi/sci/tech/2153650.stm |title=Astronomers see comet break-up |date=26 July 2002 |work=BBC News |last=Whitehouse |first=David}}</ref> A significant cometary disruption was that of [[Comet Shoemaker–Levy 9]], which was discovered in 1993. A close encounter in July 1992 had broken it into pieces, and over a period of six days in July 1994, these pieces fell into Jupiter's atmosphere—the first time astronomers had observed a collision between two objects in the Solar System.<ref>{{cite web |last=Kronk |first=Gary W. |title=D/1993 F2 Shoemaker–Levy 9 |url=http://cometography.com/pcomets/1993f2.html |work=Gary W. Kronk's Cometography |access-date=27 April 2009 |url-status=dead |archive-url=https://web.archive.org/web/20080509145539/http://cometography.com/pcomets/1993f2.html |archive-date=9 May 2008 }}</ref><ref>{{cite web |url=http://www2.jpl.nasa.gov/sl9/background.html |title=Comet Shoemaker–Levy Background |publisher=JPL |access-date=23 September 2013}}</ref> Other splitting comets include [[3D/Biela]] in 1846 and [[73P/Schwassmann–Wachmann]] from 1995 to 2006.<ref name=spitzer2006>{{cite web |date=10 May 2006 |title=Spitzer Telescope Sees Trail of Comet Crumbs |last=Whitney |first=Clavin |url=http://www.spitzer.caltech.edu/news/239-ssc2006-13-Spitzer-Telescope-Sees-Trail-of-Comet-Crumbs |access-date=16 August 2013}}</ref> Greek historian [[Ephorus]] reported that a comet split apart as far back as the winter of 372–373 BC.<ref name="great">{{cite web |title=Great Comets in History |first=Donald K. |last=Yeomans |publisher=JPL |url=http://ssd.jpl.nasa.gov/?great_comets |date=April 2007 |access-date=16 August 2013}}</ref> Comets are suspected of splitting due to thermal stress, internal gas pressure, or impact.<ref name=split>{{cite book |bibcode=2004come.book..301B |url=http://www.lpi.usra.edu/books/CometsII/7011.pdf |archive-url=https://web.archive.org/web/20090318153712/http://www.lpi.usra.edu/books/CometsII/7011.pdf |archive-date=2009-03-18 |url-status=live |title=Split comets |last1=Boehnhardt |first1=H. |date=2004 |pages=301 |journal=Comets II|doi=10.2307/j.ctv1v7zdq5.25 }}</ref>

Comets [[42P/Neujmin]] and [[53P/Van Biesbroeck]] appear to be fragments of a parent comet. Numerical integrations have shown that both comets had a rather close approach to Jupiter in January 1850, and that, before 1850, the two orbits were nearly identical.<ref name="DPS35">{{cite journal |bibcode=2003DPS....35.4705P |title=Are Comets 42P/Neujmin 3 and 53P/Van Biesbroeck Parts of one Comet? |last1=Pittichova |first1=Jand |last2=Meech |first2=Karen J. |last3=Valsecchi |first3=Giovanni B. |last4=Pittich |first4=Eduard M. |display-authors=1 |volume=35 |date=2003 |pages=1011 |journal=Bulletin of the American Astronomical Society}}</ref> Another group of comets that is the result of fragmentation episodes is the Liller comet family made of C/1988 A1 (Liller), C/1996 Q1 (Tabur), C/2015 F3 (SWAN), C/2019 Y1 (ATLAS), and [[C/2023 V5 (Leonard)]].<ref name="Sekanina-2016">{{Cite journal
  |first1     =  Zdenek |last1 = Sekanina
  |first2     =  Rainer |last2 =  Kracht
  |date       = 1 May 2016
  |title      = Pairs and Groups of Genetically Related Long-period Comets and Proposed Identity of the Mysterious Lick Object of 1921
  |journal    = [[The Astrophysical Journal]]
  |volume     = 823
  |issue      = 1
  |pages      = 2 (26 pages)
  |bibcode    = 2016ApJ...823....2S 
  |doi        = 10.3847/0004-637X/823/1/2
  |arxiv      = 1510.06445 
  |doi-access = free
 }}</ref><ref name="de la Fuente Marcos-2023">{{Cite journal
  |first1     = Carlos |last1 = de la Fuente Marcos
  |first2     = Raúl |last2 = de la Fuente Marcos
  |date       = 27 November 2023
  |title      = Second-generation Fragments of a Comet Split in the Making: The Liller Family Comets
  |journal    = Research Notes of the American Astronomical Society
  |volume     = 7
  |issue      = 11
  |pages      = 249 (3 pages)
  |bibcode    = 2023RNAAS...7..249D 
  |doi        = 10.3847/2515-5172/ad0f27
  |arxiv      = 
  |doi-access = free
 }}</ref>

Some comets have been observed to break up during their perihelion passage, including great comets [[Comet West|West]] and [[Comet Ikeya–Seki|Ikeya–Seki]]. Biela's Comet was one significant example when it broke into two pieces during its passage through the perihelion in 1846. These two comets were seen separately in 1852, but never again afterward. Instead, spectacular [[meteor showers]] were seen in 1872 and 1885 when the comet should have been visible. A minor meteor shower, the [[Andromedids]], occurs annually in November, and it is caused when Earth crosses the orbit of Biela's Comet.<ref>{{cite web |url=http://meteorshowersonline.com/showers/andromedids.html |title=The Andromedids |publisher=Meteor Showers Online |access-date=27 April 2009 |archive-url=https://web.archive.org/web/20130122144223/http://meteorshowersonline.com/showers/andromedids.html |archive-date=22 January 2013 |url-status=dead}}</ref>

Some comets meet a more spectacular end – either falling into the Sun<ref>{{cite web |title=SOHO analyses a kamikaze comet |url=http://sci.esa.int/soho/26188-soho-analyses-a-kamikaze-comet/ |publisher=European Space Agency |date=23 February 2001 |access-date=30 August 2013}}</ref> or colliding with a planet or other body. Collisions between comets and planets or moons were common in the early Solar System: some of the many craters on the Moon, for example, may have been caused by comets. A recent collision of a comet with a planet occurred in July 1994 when Comet Shoemaker–Levy 9 broke up into pieces and collided with Jupiter.<ref>{{cite web |url=http://nssdc.gsfc.nasa.gov/planetary/comet.html |title=Comet Shoemaker–Levy 9 Collision with Jupiter |access-date=30 August 2013 |publisher=National Space Science Data Center}}</ref>

{{multiple image
| direction         = horizontal
| align             = center
| total_width       = 800
| image1            = Jupiter showing SL9 impact sites.jpg
| image2            = Schwassman-Wachmann3-B-HST.gif
| image3            = C2015D1-SOHO.jpg
| image4            = 14060-Asteroid-P2013R3-Disintegration-20140306.jpg
| caption1          = Brown spots mark impact sites of [[Comet Shoemaker–Levy 9]] on Jupiter
| caption2          = The break up of [[73P/Schwassmann–Wachmann]] within three days (1995)
| caption3          = Ghost tail of C/2015 D1 (SOHO) after passage at the Sun
| caption4          = Disintegration of [[Main-belt comet#Activity|P/2013 R3]] (2014)<ref name="NASA-20140306">{{cite web |url=http://www.nasa.gov/press/2014/march/nasas-hubble-telescope-witnesses-asteroids-mysterious-disintegration-1 |title=Release 14-060: NASA's Hubble Telescope Witnesses Asteroid's Mysterious Disintegration |publisher=[[NASA]] |last1=Harrington |first1=J.D. |last2=Villard |first2=Ray |name-list-style=amp |date=6 March 2014 |access-date=6 March 2014}}</ref>
}}

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