Editing Messier 92 (section)

== Characteristics ==
It is also one of the galaxy's oldest clusters. It is around {{Convert|16|e3ly|kpc|abbr=on|lk=on}} above/below the [[galactic plane]] and {{Convert|33|e3ly|kpc|abbr=on|lk=off}} from the [[Galactic Center]].<ref name="aj133_3_1041" /> It is about 26,700 [[light-year]]s away from the [[Solar System]].The half-light radius, or radius containing the upper half of its light emission, is 1.09&nbsp;[[arcminute]]s ({{prime}}), while the tidal radius, the broadest standard measure, is 15.17{{prime}}. It appears only [[flattening|slightly flattened]]: its minor axis is about 89% ± 3% of the major.<ref name="apj721_2_1790" />

Characteristic of other globulars, it has little of the elements other than hydrogen and helium; astronomers term this low [[metallicity]]. Specifically, relative to the [[Sun]], its iron abundance is [Fe/H]&nbsp;= &ndash;2.32&nbsp;[[dex (decimal exponent)|dex]],<ref name="aj133_3_1041" /> which is 0.5% of 1.0, on this [[log10|logarithmic]] scale, the solar abundance.<ref>Since 10<sup>−2.29</sup> = 0.00513.</ref> This puts the estimated age range for the cluster at {{nowrap|11 ± 1.5 billion years}}.<ref>{{Cite journal|last1=Di Cecco|first1=A.|last2=Becucci|first2=R.|last3=Bono|first3=G.|last4=Monelli|first4=M.|last5=Stetson|first5=P. B.|last6=Degl'Innocenti|first6=S.|last7=Moroni|first7=P. G. Prada|last8=Nonino|first8=M.|last9=Weiss|first9=A.|last10=Buonanno|first10=R.|last11=Calamida|first11=A.|date=2010-06-27|title=On the absolute age of the Globular Cluster M92|journal=Publications of the Astronomical Society of the Pacific|volume=122|issue=895|pages=991–999|language=en|doi=10.1086/656017|arxiv=1006.5217|bibcode=2010PASP..122..991D |doi-access=free}}</ref>

Its true diameter is 108 ly, and may have a mass corresponding to 330,000 suns.<ref name=":0">{{Cite web |title=Messier Object 92 |url=https://www.messier.seds.org/m/m092.html |access-date=2022-05-28 |website=www.messier.seds.org}}</ref>

The cluster is not yet in, nor guaranteed to undergo, [[core collapse (cluster)|core collapse]] and the core radius figures as about 2&nbsp;[[arcsecond]]s ({{pprime}}).<ref name="aj133_3_1041" /> It is an [[Pieter Oosterhoff|Oosterhoff]] type II (OoII) globular cluster, which means it belongs to the group of metal-poor clusters with longer period [[RR Lyrae variable]] stars. The 1997 ''Catalogue of Variable Stars in Globular Clusters'' listed 28 candidate variable stars in the cluster, although only 20 have been confirmed. As of 2001, there are 17 known RR Lyrae variables in Messier 92.<ref name="aaa369_862" /> 10 X-ray sources have been detected within the 1.02&nbsp;arcminute half-mass radius of the cluster, of which half are candidate [[cataclysmic variable star]]s.<ref name="apj736_2_158" /><ref>{{Cite journal |last1=Ferraro |first1=F. R. |last2=Paltrinieri |first2=B. |last3=Fusi Pecci |first3=F. |last4=Rood |first4=R. T. |last5=Dorman |first5=B. |date=1998-01-01 |title=Faint UV Objects in the Core of Ggcs: a New Subclass of Cvs? |journal=Ultraviolet Astrophysics Beyond the IUE Final Archive |url=https://ui.adsabs.harvard.edu/abs/1998ESASP.413..561F |volume=413 |pages=561|bibcode=1998ESASP.413..561F}}</ref>

M92 is approaching us at 112 km/sec. Its coordinates indicate that the Earth's North [[Celestial pole|Celestial Pole]] periodically passes less than one degree of this cluster during the precession of Earth's axis. Thus, M92 was a "Polarissima Borealis", or "North Cluster", about 12,000 years ago (10,000 BC), and it will again in about 14,000 years (16,000 AD).<ref name=":0" />{{-}}

The multiple stellar populations in this cluster, revealing that it hosts at least two stellar generations of stars named 1G and 2G, as well as two distinct groups of 2G stars (2GA and 2GB).<ref>{{cite news |last1=World |first1=FTT |title=Astronomers discover new insights into multiple stellar populations in Messier 92 using James Webb |url=https://www.followthistrendingworld.com/post/astronomers-discover-new-insights-into-multiple-stellar-populations-in-messier-92-using-james-webb}}</ref> The helium abundances of 2GA and 2GB stars have higher mass fractions than that of the 1G stars by 0.01 and 0.04, respectively.