Changes

==Classification==

==Classification==

In 1930, R.J Trumpler introduced a classification system for open clusters based on three attributes.  The first attribute is according to how concentrated the cluster is towards it's center, ranging from I-IV:

In 1930, Swiss-American astronomer R.J Trumpler introduced a classification system for open clusters, later known as the ''Trumpler classification'', based on three defining attributes.<ref>http://books.google.com/books?id=40JzBYGREL0C&pg=PA74&dq=%22Trumpler+classification%22&ei=bMLDSLHnD5TqjgHkqeTrDQ&sig=ACfU3U0fxdckqWt_w6eawA44vGIJmi2yJg#v=onepage&q=%22Trumpler%20classification%22&f=false</ref> The first attribute is according to how concentrated the cluster is towards it's center, ranging from I-IV:

*I - Detached from the surrounding stars with strong concentration towards the cluster center

*I - Detached from the surrounding stars with strong concentration towards the cluster center

*r - Cluster has over 100 stars, rich

*r - Cluster has over 100 stars, rich

If the cluster lies within a [[nebula|nebulous structure]] it's classification is appended with an 'n'.  Under this classification method for example, the Pleiades is classified as '''I3rn''' (Strong concentration towards the center, richly populated with stars that have a wide range in brightness, with nebulous material present). <ref>http://adsabs.harvard.edu/cgi-bin/bib_query?1930LicOB.420..154T</ref>

If the cluster lies within a [[nebula|nebulous structure]] it's classification is appended with an 'n'.  Under this classification method for example, the [[Pleiades]] is classified as '''I3rn''' (Strong concentration towards the center, richly populated with stars that have a wide range in brightness, with nebulous material present). <ref>http://adsabs.harvard.edu/cgi-bin/bib_query?1930LicOB.420..154T</ref>

==Old Universe View==

==Old Universe View==