Editing Pleiades (section)

== Age and future evolution ==
[[File:Pleiades-motion.png|thumb|Stars of Pleiades with color and 10,000-year backward proper motion shown]]
Ages for star clusters may be estimated by comparing the [[Hertzsprung–Russell diagram]] for the cluster with theoretical models of [[stellar evolution]]. Using this technique, ages for the Pleiades of between 75 and 150 million years have been estimated. The wide spread in estimated ages is a result of uncertainties in stellar evolution models, which include factors such as [[convective overshoot]], in which a [[convection|convective]] zone within a star penetrates an otherwise non-convective zone, resulting in higher apparent ages.{{citation needed|date=September 2023}}

Another way of estimating the age of the cluster is by looking at the lowest-mass objects. In normal [[main-sequence]] stars, [[lithium]] is rapidly destroyed in [[nuclear fusion]] reactions. [[Brown dwarf]]s can retain their lithium, however. Due to lithium's very low ignition temperature of 2.5 × 10<sup>6</sup> K, the highest-mass brown dwarfs will burn it eventually, and so determining the highest mass of brown dwarfs still containing lithium in the cluster may give an idea of its age. Applying this technique to the Pleiades gives an age of about 115 million years.<ref>
{{cite journal |last1=Basri |first1=Gibor |last2=Marcy |first2=Geoffrey W. |last3=Graham |first3=James R. |title=Lithium in Brown Dwarf Candidates: The Mass and Age of the Faintest Pleiades Stars |year=1996 |journal=[[The Astrophysical Journal]] |volume=458 |pages=600–609 |doi=10.1086/176842 |bibcode=1996ApJ...458..600B }}</ref><ref>
{{cite journal
 |display-authors=4
 |author=Ushomirsky, G.
 |author2=Matzner, C.
 |author3=Brown, E.
 |author4=Bildsten, L.
 |author5=Hilliard, V.
 |author6=Schroeder, P.
 |date=1998
 |title=Light-Element Depletion in Contracting Brown Dwarfs and Pre-Main-Sequence Stars
 |journal=[[Astrophysical Journal]]
 |volume=497 |issue=1
 |pages=253–266
 |bibcode=1998ApJ...497..253U
 |doi=10.1086/305457
|arxiv = astro-ph/9711099 |s2cid=14674869
 }}</ref>

The cluster is [[relative motion|slowly moving]] in the direction of the feet of what is currently the constellation of [[Orion (constellation)|Orion]]. Like most open clusters, the Pleiades will not stay gravitationally bound forever. Some component stars will be ejected after close encounters with other stars; others will be stripped by tidal gravitational fields. Calculations suggest that the cluster will take approximately 250 million years to disperse, because of gravitational interactions with [[molecular cloud|giant molecular clouds]] and the [[Spiral galaxy|spiral arms]] of our galaxy hastening its demise.<ref>
{{cite journal
 |author=Converse, Joseph M.
 |author2=Stahler, Steven W.
 |name-list-style=amp
 |date=2010
 |title=The dynamical evolution of the Pleiades
 |journal=[[Monthly Notices of the Royal Astronomical Society]]
 |volume=405 |issue=1
 |pages=666–680
 |doi=10.1111/j.1365-2966.2010.16505.x
 |doi-access=free
 |bibcode=2010MNRAS.405..666C
 |arxiv = 1002.2229 |s2cid=54611261
 }}</ref>