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Line 9: − − ==Cluster Formation== − − It is believed that open clusters are initially formed when a large molecular cloud collapses due to nearby gravitational interactions or [[supernova]]. As the cloud collapses, it will fragment into increasingly smaller parts, it is some of these fragments of gas and material that eventually result [[stellar evolution|in the creation of new stars]]. Eventually the hottest and most massive of these stars drive away the remaining gasses through their stellar winds and radiation and star formation ceases.<ref>http://adsabs.harvard.edu/abs/1991MNRAS.249...76B</ref> − − Over time as an open cluster drifts through space, the individual stars of the loosely bound cluster slowly begin to drift away due to gravitational interactions with the rest of the galaxy. It is estimated that after few hundred million years the cluster would lose most of the member stars as individual stars orbiting the core of a [[galaxy]], connected only by their similar orbits in a disassociated group.<ref>http://adsabs.harvard.edu/abs/1998PASP..110.1117D</ref> Line 38:
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An '''open cluster''', sometimes referred to as an '''open star cluster''' or a '''galactic cluster''', is a group of physically related [[star|stars]] that have similar chemical composition and age held together by mutual [[gravity]]. In contrast to a [[globular cluster|globular clusters]], the stars of an open cluster are only loosely gravitationally bound to each other. Open clusters have only been observed in galaxies with active star formation, such as [[spiral galaxy|spiral]] and [[irregular galaxy|irregular galaxies]], for spiral galaxies, they are found within the spiral arms.<ref>http://adsabs.harvard.edu/abs/1979stcl.book.....P</ref> These clusters are made up of [[metallicity|younger population I stars]] and can be traced back to [[molecular cloud|molecular clouds]] where they formed. The youngest clusters may still be contained in the clouds they birthed from, illuminating it.<ref>http://adsabs.harvard.edu/abs/1962ApJ...136.1135J</ref> At current count, there are over 1,100 known open clusters in the [[Milky Way]] alone, although this may be only a small percentage of the total.<ref name="am">http://www.maa.clell.de/Messier/open.html</ref>
An '''open cluster''', sometimes referred to as an '''open star cluster''' or a '''galactic cluster''', is a group of physically related [[star|stars]] that have similar chemical composition held together by mutual [[gravity]]. In contrast to a [[globular cluster|globular clusters]], the stars of an open cluster are only loosely gravitationally bound to each other. Open clusters have only been observed in galaxies with active star formation, such as [[spiral galaxy|spiral]] and [[irregular galaxy|irregular galaxies]], for spiral galaxies, they are found within the spiral arms.<ref>http://adsabs.harvard.edu/abs/1979stcl.book.....P</ref> These clusters are made up of [[metallicity|population I stars]]. Some clusters may still be contained in interstellar clouds, illuminating the clouds.<ref>http://adsabs.harvard.edu/abs/1962ApJ...136.1135J</ref> At current count, there are over 1,100 known open clusters in the [[Milky Way]] alone, although this may be only a small percentage of the total.<ref name="am">http://www.maa.clell.de/Messier/open.html</ref>
The clusters themselves range from large conglomerates of thousands of stars to sparse clusters of only a dozen or less. The core or center of these clusters are a few light years across with an average density of a star per 1.5 cubic light years, about 500 times as dense as our solar neighborhood.
The clusters themselves range from large conglomerates of thousands of stars to sparse clusters of only a dozen or less. The core or center of these clusters are a few light years across with an average density of a star per 1.5 cubic light years, about 500 times as dense as our solar neighborhood.
Although there are various recording of the related stars of open clusters as far back as [[Ptolemy]] in 138 A.D, it wasn't until 1767 that the stars were recognized as such when [[Reverend]] [[John Michell]] first postulated that the stars of an open clusters had to be related because the chance of finding even one such cluster if they just happen to be a collection of unrelated stars were too astronomical.<ref name="am">http://www.maa.clell.de/Messier/open.html</ref> It wasn't until 1869 that the relation of stars in an open cluster was conclusively shown. That year Richard Proctor in his study of the Pleiades and the [[Ursa Major|Ursa Major Moving Cluster]], demonstrated using spectroscopy that the stars of the clusters have the same [[radical velocity]], indicating they are bound to each other by gravity. Proctor also showed that the stars of such clusters were all about the same distance from the [[Earth]], further showing they were moving together and were related.<ref>http://adsabs.harvard.edu/cgi-bin/bib_query?1869RSPS...18..169P</ref>
Although there are various recording of the related stars of open clusters as far back as [[Ptolemy]] in 138 A.D, it wasn't until 1767 that the stars were recognized as such when [[Reverend]] [[John Michell]] first postulated that the stars of an open clusters had to be related because the chance of finding even one such cluster if they just happen to be a collection of unrelated stars were too astronomical.<ref name="am">http://www.maa.clell.de/Messier/open.html</ref> It wasn't until 1869 that the relation of stars in an open cluster was conclusively shown. That year Richard Proctor in his study of the Pleiades and the [[Ursa Major|Ursa Major Moving Cluster]], demonstrated using spectroscopy that the stars of the clusters have the same [[radical velocity]], indicating they are bound to each other by gravity. Proctor also showed that the stars of such clusters were all about the same distance from the [[Earth]], further showing they were moving together and were related.<ref>http://adsabs.harvard.edu/cgi-bin/bib_query?1869RSPS...18..169P</ref>
==Classification==
==Classification==
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>
==Evolutionist Beliefs==
Old-Earth creationists and evolutionist believe that open clusters are initially formed when a large molecular cloud collapses due to nearby gravitational interactions or [[supernova]]. They believe that as the cloud collapses, it will fragment into increasingly smaller parts; they think that some of these fragments of gas and material that eventually result [[stellar evolution|in the creation of new stars]]. Eventually, according to these theories, the hottest and most massive of these stars drive away the remaining gasses through their stellar winds and radiation and star formation ceases.<ref>http://adsabs.harvard.edu/abs/1991MNRAS.249...76B</ref>
As an open cluster drifts through space, evolutionists believe, the individual stars of the loosely bound cluster slowly begin to drift away due to gravitational interactions with the rest of the galaxy. They believe that after few hundred million years the cluster would lose most of the member stars as individual stars orbiting the core of a [[galaxy]], connected only by their similar orbits in a disassociated group.<ref>http://adsabs.harvard.edu/abs/1998PASP..110.1117D</ref>
[[Category:Astronomy]]
[[Category:Astronomy]]