Editing Globular cluster (section)

==Planets==
Astronomers are searching for exoplanets of stars in globular star clusters.<ref>{{cite news |last=Ricard |first=Elise |date=15 January 2016 |title=Planet locations, a supernova, and a black hole |department=Space Friday |publisher=[[California Academy of Sciences]] |url=https://www.calacademy.org/explore-science/space-friday-planet-locations-a-supernova-and-a-black-hole |access-date=May 15, 2016}}</ref> A search in 2000 for [[giant planet]]s in the globular cluster {{nobr|[[47 Tucanae]]}} came up negative, suggesting that the abundance of heavier elements&nbsp;– low in globular clusters&nbsp;– necessary to build these planets may need to be at least 40% of the Sun's abundance. Because [[terrestrial planet]]s are built from heavier elements such as silicon, iron and magnesium, member stars have a far lower likelihood of hosting Earth-mass planets than stars in the solar neighborhood. Globular clusters are thus unlikely to host [[Habitable planet|habitable terrestrial planet]]s.<ref name=icarus152_1_185>{{cite journal | last1=Gonzalez | first1=Guillermo | author-link1=Guillermo Gonzalez (astronomer) | last2=Brownlee | first2=Donald | author-link2=Donald E. Brownlee |last3=Ward | first3=Peter |date=July 2001 | title=The galactic habitable zone: Galactic chemical evolution | journal=[[Icarus (journal)|Icarus]] | volume=152 | issue=1 | pages=185–200 | doi=10.1006/icar.2001.6617 | bibcode=2001Icar..152..185G | arxiv = astro-ph/0103165 | s2cid=18179704 }}</ref>

A giant planet was found in the globular cluster {{nobr|[[Messier 4]]}}, orbiting a pulsar in the binary star system {{nobr|PSR B1620-26}}. The planet's [[Orbital eccentricity|eccentric]] and [[Inclination|highly inclined]] orbit suggests it may have been formed around another star in the cluster, then "exchanged" into its current arrangement.<ref name=sigurdsson_et_al2007>{{cite book | last1=Sigurdsson | first1=S. | last2=Stairs | first2=I.H. | author-link2=Ingrid Stairs | last3=Moody | first3=K. | last4=Arzoumanian | first4=K.M.Z. | last5=Thorsett | first5=S.E. |author-link5=Stephen Thorsett | year=2008 | chapter=Planets around pulsars in globular clusters | editor1-first=D. | editor1-last=Fischer | editor2-first=F.A. | editor2-last=Rasio | editor3-first=S.E. | editor3-last=Thorsett | editor-link3=Stephen Thorsett |editor4-first=A. | editor4-last=Wolszczan |editor-link4=Aleksander Wolszczan | title=Extreme Solar Systems |series=ASP Conference Series | volume=398 | page=119 | publisher=[[Astronomical Society of the Pacific]] | bibcode=2008ASPC..398..119S }}</ref> The likelihood of close encounters between stars in a globular cluster can disrupt planetary systems; some planets break free to become [[rogue planet]]s, orbiting the galaxy. Planets orbiting close to their star can become disrupted, potentially leading to [[orbital decay]] and an increase in orbital eccentricity and tidal effects.<ref name=apj697_1_458>{{cite journal | display-authors=1 | last1=Spurzem | first1=R. |author-link1=Rainer Spurzem | last2=Giersz | first2=M. | last3=Heggie | first3=D.C. | author-link3=Douglas C. Heggie |last4=Lin | first4=D.N.C. |date=May 2009 | title=Dynamics of planetary systems in star clusters | journal=[[The Astrophysical Journal]] | volume=697 | issue=1 | pages=458–482 | doi=10.1088/0004-637X/697/1/458 | bibcode=2009ApJ...697..458S |arxiv = astro-ph/0612757 | s2cid=119083161 }}</ref> In 2024, a gas giant or brown dwarf was found to closely orbit the pulsar "M62H", where the name indicates that the planetary system belongs to the globular cluster [[Messier 62]].<ref>{{Cite journal |last1=Vleeschower |first1=L. |last2=Corongiu |first2=A. |last3=Stappers |first3=B. W. |last4=Freire |first4=P. C. C. |last5=Ridolfi |first5=A. |last6=Abbate |first6=F. |last7=Ransom |first7=S. M. |last8=Possenti |first8=A. |last9=Padmanabh |first9=P. V. |last10=Balakrishnan |first10=V. |last11=Kramer |first11=M. |last12=Krishnan |first12=V. Venkatraman |last13=Zhang |first13=L. |last14=Bailes |first14=M. |last15=Barr |first15=E. D. |date=2024-03-01 |title=Discoveries and timing of pulsars in M62 |url=https://ui.adsabs.harvard.edu/abs/2024MNRAS.tmp..838V |journal=Monthly Notices of the Royal Astronomical Society |volume=530 |issue=2 |pages=1436–1456 |doi=10.1093/mnras/stae816 |doi-access=free |arxiv=2403.12137 |bibcode=2024MNRAS.530.1436V |issn=0035-8711}}</ref>