Editing Globular cluster (section)

===Classification===
{{Main|Shapley–Sawyer Concentration Class}}

Shapley was later assisted in his studies of clusters by [[Henrietta Swope]] and [[Helen Sawyer Hogg]]. In 1927–1929, Shapley and Sawyer categorized clusters by the degree of concentration of stars toward each core. Their system, known as the [[Shapley–Sawyer Concentration Class]], identifies the most concentrated clusters as Class&nbsp;I and ranges to the most diffuse Class&nbsp;XII.<ref group="lower-alpha">The [[Shapley–Sawyer Concentration Class|Concentration Class]] is sometimes given with Arabic numerals (Classes&nbsp;1–12) rather than [[Roman numeral]]s.</ref><ref name=Hogg1965>{{cite journal |last=Hogg |first=Helen Battles Sawyer |year=1965 |title=Harlow Shapley and globular glusters |journal=[[Publications of the Astronomical Society of the Pacific]] |volume=77 |issue=458 |pages=336–346 |bibcode=1965PASP...77..336S |doi=10.1086/128229 |doi-access=free }}</ref> Astronomers from the [[Pontifical Catholic University of Chile]] proposed a new type of globular cluster on the basis of observational data in 2015: [[Dark globular cluster]]s.<ref>{{cite news |title=The Very Large Telescope discovers new kind of globular star cluster |date=May 13, 2015 |magazine=[[Astronomy (magazine)|Astronomy]] |url=http://www.astronomy.com/news/2015/05/the-very-large-telescope-discovers-new-kind-of-globular-star-cluster |access-date=May 14, 2015 }}</ref>
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