Editing Quark star (section)

==Observed overdense neutron stars==
At least under the assumptions mentioned above, the probability of a given neutron star being a quark star is low,{{citation needed|date=March 2014}} so in the Milky Way there would only be a small population of quark stars. If it is correct, however, that overdense neutron stars can turn into quark stars, that makes the possible number of quark stars higher than was originally thought, as observers would be looking for the wrong type of star.{{citation needed|date=May 2018}}

A neutron star without deconfinement to quarks and higher densities cannot have a rotational period shorter than a millisecond; even with the unimaginable gravity of such a condensed object the centrifugal force of faster rotation would eject matter from the surface, so detection of a pulsar of millisecond or less period would be strong evidence of a quark star.

Observations released by the [[Chandra X-ray Observatory]] on April 10, 2002, detected two possible quark stars, designated [[RX J1856.5−3754]] and [[3C 58]], which had previously been thought to be neutron stars. Based on the known laws of physics, the former appeared much smaller and the latter much colder than it should be, suggesting that they are composed of material denser than [[neutron-degenerate matter]]. However, these observations are met with skepticism by researchers who say the results were not conclusive;<ref name="Truemper2004">{{cite journal |last1=Trümper |first1=Joachim E. |last2=Burwitz |first2=Vadim |last3=Haberl |first3=Frank W. |last4=Zavlin |first4=Vyatcheslav E. |title=The puzzles of RX J1856.5-3754: neutron star or quark star? |journal=Nuclear Physics B: Proceedings Supplements |date=June 2004 |volume=132 |pages=560–565 |doi=10.1016/j.nuclphysbps.2004.04.094 |bibcode=2004NuPhS.132..560T |arxiv=astro-ph/0312600 |citeseerx=10.1.1.314.7466 |s2cid=425112 }}</ref> and since the late 2000s, the possibility that [[RX J1856.5-3754|RX J1856]] is a quark star has been excluded.

Another star, [[XTE J1739-285]],<ref>Shiga, David; [https://www.newscientist.com/article/dn11221?DCMP=NLC-nletter&nsref=dn11221 "Fastest spinning star may have exotic heart"] {{Webarchive|url=https://web.archive.org/web/20120825035205/http://www.newscientist.com/article/dn11221?DCMP=NLC-nletter&nsref=dn11221 |date=2012-08-25 }}, ''New Scientist'', 2007 February 20</ref> has been observed by a team led by Philip Kaaret of the [[University of Iowa]] and reported as a possible quark star candidate.

In 2006, You-Ling Yue et al., from [[Peking University]], suggested that [[PSR B0943+10]] may in fact be a low-mass quark star.<ref>{{cite journal |first1=You-Ling |last1=Yue |first2=Xiao-Hong |last2=Cui |first3=Ren-Xin |last3=Xu |title=Is PSR B0943+10 a low-mass quark star? |journal=Astrophysical Journal |volume=649 |issue=2 |pages=L95–L98 |year=2006 |arxiv=astro-ph/0603468 |doi=10.1086/508421 |bibcode=2006ApJ...649L..95Y |s2cid=18183996 }}</ref>

It was reported in 2008 that observations of supernovae [[SN 2006gy]], [[SN 2005gj]] and [[SN 2005ap]] also suggest the existence of quark stars.<ref>Chadha, Kulvinder Singh; [http://astronomynow.com/080604Secondsupernovaepointtoquarkstars.html "Second Supernovae Point to Quark Stars"] {{Webarchive|url=https://web.archive.org/web/20100125145543/http://astronomynow.com/080604Secondsupernovaepointtoquarkstars.html |date=2010-01-25 }}, ''Astronomy Now Online'', 2008 June 04</ref> It has been suggested that the collapsed core of supernova [[SN 1987A]] may be a quark star.<ref>{{cite journal |author1=Chan |author2=Cheng |author3=Harko |author4=Lau |author5=Lin |author6=Suen |author7=Tian |doi=10.1088/0004-637X/695/1/732 |journal=Astrophysical Journal |title=Could the compact remnant of SN 1987A be a quark star? |volume=695 |issue=1 |pages=732–746 |year=2009 |arxiv=0902.0653|bibcode = 2009ApJ...695..732C |s2cid=14402008 }}</ref><ref>Parsons, Paul; [https://www.newscientist.com/article/mg20126964.700-quark-star-may-hold-secret-to-early-universe.html "Quark star may hold secret to early universe"] {{Webarchive|url=https://web.archive.org/web/20150318100318/http://www.newscientist.com/article/mg20126964.700-quark-star-may-hold-secret-to-early-universe.html |date=2015-03-18 }}, ''New Scientist'', 2009 February 18</ref>

In 2015, Zi-Gao Dai et al. from Nanjing University suggested that Supernova [[ASASSN-15lh]] is a newborn strange quark star.<ref>{{Cite journal |title=The Most Luminous Supernova ASASSN-15lh: Signature of a Newborn Rapidly-Rotating Strange Quark Star |arxiv=1508.07745 |date=2015-08-31 |first1=Zi-Gao |last1=Dai |first2=Shan-Qin |last2=Wang |first3=J. S. |last3=Wang |first4=Ling-Jun |last4=Wang |first5=Yun-Wei |last5=Yu |doi=10.3847/0004-637X/817/2/132 |volume=817 |issue=2 |journal=The Astrophysical Journal |page=132 |bibcode=2016ApJ...817..132D |s2cid=54823427 |doi-access=free }}</ref>

In 2022 it was suggested that GW190425, which likely formed as a merger between two neutron stars giving off gravitational waves in the process, could be a quark star.<ref>{{cite web | url=https://www.space.com/strange-quark-stars-from-neutron-star-mergers | title=Strange quark star may have formed from a lucky cosmic merger | website=[[Space.com]] | date=16 September 2022 }}</ref>