Editing RR Lyrae variable (section)

==Distribution==
[[Image:Variable stars close to the Galactic Centre.jpg|thumb|right|RR Lyrae-type variable stars close to the galactic center from the [[Vista Variables in the Via Lactea|VVV]] [[European Southern Observatory|ESO]] public survey]]
RR Lyrae stars were formerly called "cluster variables" because of their strong (but not exclusive) association with [[globular clusters]]; conversely, over 80% of all variables known in globular clusters are RR Lyraes.<ref name=clement>{{cite journal|bibcode=2001AJ....122.2587C|arxiv=astro-ph/0108024|title=Variable Stars in Galactic Globular Clusters|journal=The Astronomical Journal|volume=122|issue=5|pages=2587–2599|last1=Clement|first1=Christine M.|last2=Muzzin|first2=Adam|last3=Dufton|first3=Quentin|last4=Ponnampalam|first4=Thivya|last5=Wang|first5=John|last6=Burford|first6=Jay|last7=Richardson|first7=Alan|last8=Rosebery|first8=Tara|last9=Rowe|first9=Jason|last10=Hogg|first10=Helen Sawyer|year=2001|doi=10.1086/323719|s2cid=38359010 }}</ref> RR Lyrae stars are found at all galactic latitudes, as opposed to [[classical Cepheids]], which are strongly associated with the galactic plane.

Because of their old age, RR Lyraes are commonly used to trace certain populations in the Milky Way, including the halo and thick disk.<ref>{{Cite journal|last1=Vozyakova|first1=O. V.|last2=Sefako|first2=R.|last3=Rastorguev|first3=A. S.|last4=Kravtsov|first4=V. V.|last5=Kniazev|first5=A. Y.|last6=Berdnikov|first6=L. N.|last7=Dambis|first7=A. K.|date=2013-11-11|title=RR Lyrae variables: visual and infrared luminosities, intrinsic colours and kinematics|url=https://academic.oup.com/mnras/article/435/4/3206/1030228|journal=Monthly Notices of the Royal Astronomical Society|language=en|volume=435|issue=4|pages=3206–3220|doi=10.1093/mnras/stt1514|doi-access=free |issn=0035-8711|arxiv=1308.4727}}</ref>

Several times as many RR Lyraes are known as all Cepheids combined; in the 1980s, about 1900 were known in globular clusters. Some estimates have about 85,000 in the Milky Way.<ref name="smith2004">{{cite book|last= Smith|first=Horace A.|title=RR Lyrae Stars|url=https://books.google.com/books?id=dMv_r82moCQC|year=2004|publisher=Cambridge University Press|isbn=978-0-521-54817-5}}</ref>

Though [[binary star]] systems are common for typical stars, RR Lyraes are very rarely observed in binaries.<ref>{{cite journal|last1=Hajdu|first1=G.|last2=Catelan|first2=M.|last3=Jurcsik|first3=J.|last4=Dékány|first4=I.|last5=Drake|first5=A.J.|last6=Marquette|first6=B.|title=New RR Lyrae variables in binary systems|journal=Monthly Notices of the Royal Astronomical Society|volume=449|issue=1|pages=L113–L117|doi=10.1093/mnrasl/slv024|arxiv = 1502.01318 |bibcode = 2015MNRAS.449L.113H |year=2015|doi-access=free }}</ref>