Editing Pleiades (section)

== Composition ==
[[File:M45map.jpg|thumb|right|A map of the Pleiades]]
The cluster core radius is approximately 8 [[light-year]]s and [[tidal radius]] is approximately 43 light-years. The cluster contains more than 1,000 statistically confirmed members, not counting the number that would be added if all [[binary star]]s could be resolved.<ref name="Adams, Joseph D. 2053">
{{cite journal
 |display-authors=4
 |author=Adams, Joseph D.
 |author2=Stauffer, John R.
 |author3=Monet, David G.
 |author4=Skrutskie, Michael F.
 |author5=Beichman, Charles A.
 |date=2001
 |title=The Mass and Structure of the Pleiades Star Cluster from 2MASS
 |journal=[[Astronomical Journal]]
 |volume=121 |pages=2053–2064
 |bibcode=2001AJ....121.2053A
 |doi=10.1086/319965
|arxiv = astro-ph/0101139
 |issue=4 |s2cid=17994583
 }}</ref> Its light is dominated by young, hot [[stellar classification|blue stars]], up to 14 of which may be seen with the naked eye, depending on local observing conditions and visual acuity of the observer. The brightest stars form a shape somewhat similar to that of [[Ursa Major]] and [[Ursa Minor]]. The total mass contained in the cluster is estimated to be approximately 800 [[solar mass]]es and is dominated by fainter and redder stars{{Clarification needed|reason=Do we mean that the MASS consists mostly of fainter and redder stars, or that the POPULATION consists mostly of fainter and redder stars?|date=May 2024}}.<ref name="Adams, Joseph D. 2053"/> An estimate of the frequency of [[binary star]]s in the Pleiades is approximately 57%.<ref>{{cite journal|doi=10.3847/1538-4357/ac1585|title=Long-term Spectroscopic Survey of the Pleiades Cluster: The Binary Population|year=2021|last1=Torres|first1=Guillermo|last2=Latham|first2=David W.|last3=Quinn|first3=Samuel N.|journal=The Astrophysical Journal|volume=921|issue=2|page=117|arxiv=2107.10259|bibcode=2021ApJ...921..117T|s2cid=236171384 |doi-access=free }}</ref>

The cluster contains many [[brown dwarf]]s, such as [[Teide 1]]. These are objects with less than approximately 8% of the [[Sun]]'s mass, insufficient for [[nuclear fusion]] reactions to start in their cores and become proper stars. They may constitute up to 25% of the total population of the cluster, although they contribute less than 2% of the total mass.<ref>
{{cite journal
 |author=Moraux, E.
 |author2=Bouvier, J.
 |author3=Stauffer, J. R.
 |author4=Cuillandre, J.-C.
 |date=2003
 |title=Brown in the Pleiades cluster: Clues to the substellar mass function
 |journal=[[Astronomy and Astrophysics]]
 |volume=400 |pages=891–902
 |bibcode=2003A&A...400..891M
 |doi=10.1051/0004-6361:20021903
|arxiv = astro-ph/0212571
 |issue=3 |s2cid=17613925
 }}</ref> Astronomers have made great efforts to find and analyze brown dwarfs in the Pleiades and other young clusters, because they are still relatively bright and observable, while brown dwarfs in older clusters have faded and are much more difficult to study.