http://www.citydeepsky.com/wiki/index.php?title=Open_cluster&feed=atom&action=historyOpen cluster - Revision history2024-03-28T22:10:37ZRevision history for this page on the wikiMediaWiki 1.19.17http://www.citydeepsky.com/wiki/index.php?title=Open_cluster&diff=2943&oldid=prevEvilscientist: add wikilink2010-07-22T02:08:43Z<p>add wikilink</p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Image:M45.jpg|float|thumb|250px|Pleiades]]</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Image:M45.jpg|float|thumb|250px|Pleiades]]</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>Open star clusters are groups of stars without a defined shape and generally only have a few hundred members. These groupings are loosely held together by their mutual gravitation and have a common age and origin<ref name="Abell">Abell, George O, <u>Exploration of the Universe</u>, 4th ed</ref>. This makes them very useful to astronomy as this has given science much insight into stellar evolution by looking at various open clusters of differing ages. This eventually lead to the ability to determine the age of star clusters to some accuracy<ref name="freedman">Freedman, Roger A. and Kaufmann III, William J., <u>Universe</u>, 8th ed.</ref>. As open clusters are only weakly bound gravitationally, they eventually disperse as they orbit the galaxy due to interactions with other stars.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>Open star clusters are groups of stars without a defined shape and generally only have a few hundred members. These groupings are loosely held together by their mutual gravitation and have a common age and origin<ref name="Abell">Abell, George O, <u>Exploration of the Universe</u>, 4th ed</ref>. This makes them very useful to astronomy as this has given science much insight into <ins class="diffchange diffchange-inline">[[</ins>stellar evolution<ins class="diffchange diffchange-inline">]] </ins>by looking at various open clusters of differing ages. This eventually lead to the ability to determine the age of star clusters to some accuracy<ref name="freedman">Freedman, Roger A. and Kaufmann III, William J., <u>Universe</u>, 8th ed.</ref>. As open clusters are only weakly bound gravitationally, they eventually disperse as they orbit the galaxy due to interactions with other stars.</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>To the observer, the appearance of an open cluster can vary quite substantially. Sometimes only a few stars are visible for some clusters and sometimes there are so many stars in a cluster, they blend into a blur. Often the observing instrument has much to do with how a cluster appears. Some clusters in binoculars or very small [[telescope|telescopes]] appear as a faint fuzzy patch which, when observed through a larger telescope, resolve into individual stars, [[M37]] for example. Other clusters just look like a group of stars in the same point in the sky regardless of the instrument used. It is notable that two quite well known open clusters, [[Hyades |</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>To the observer, the appearance of an open cluster can vary quite substantially. Sometimes only a few stars are visible for some clusters and sometimes there are so many stars in a cluster, they blend into a blur. Often the observing instrument has much to do with how a cluster appears. Some clusters in binoculars or very small [[telescope|telescopes]] appear as a faint fuzzy patch which, when observed through a larger telescope, resolve into individual stars, [[M37]] for example. Other clusters just look like a group of stars in the same point in the sky regardless of the instrument used. It is notable that two quite well known open clusters, [[Hyades |</div></td></tr>
</table>Evilscientisthttp://www.citydeepsky.com/wiki/index.php?title=Open_cluster&diff=2797&oldid=prevEvilscientist: add telescope link2009-11-19T01:37:55Z<p>add telescope link</p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Open star clusters are groups of stars without a defined shape and generally only have a few hundred members. These groupings are loosely held together by their mutual gravitation and have a common age and origin<ref name="Abell">Abell, George O, <u>Exploration of the Universe</u>, 4th ed</ref>. This makes them very useful to astronomy as this has given science much insight into stellar evolution by looking at various open clusters of differing ages. This eventually lead to the ability to determine the age of star clusters to some accuracy<ref name="freedman">Freedman, Roger A. and Kaufmann III, William J., <u>Universe</u>, 8th ed.</ref>. As open clusters are only weakly bound gravitationally, they eventually disperse as they orbit the galaxy due to interactions with other stars.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Open star clusters are groups of stars without a defined shape and generally only have a few hundred members. These groupings are loosely held together by their mutual gravitation and have a common age and origin<ref name="Abell">Abell, George O, <u>Exploration of the Universe</u>, 4th ed</ref>. This makes them very useful to astronomy as this has given science much insight into stellar evolution by looking at various open clusters of differing ages. This eventually lead to the ability to determine the age of star clusters to some accuracy<ref name="freedman">Freedman, Roger A. and Kaufmann III, William J., <u>Universe</u>, 8th ed.</ref>. As open clusters are only weakly bound gravitationally, they eventually disperse as they orbit the galaxy due to interactions with other stars.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>To the observer, the appearance of an open cluster can vary quite substantially. Sometimes only a few stars are visible for some clusters and sometimes there are so many stars in a cluster, they blend into a blur. Often the observing instrument has much to do with how a cluster appears. Some clusters in binoculars or very small telescopes appear as a faint fuzzy patch which, when observed through a larger telescope, resolve into individual stars, [[M37]] for example. Other clusters just look like a group of stars in the same point in the sky regardless of the instrument used. It is notable that two quite well known open clusters, [[Hyades |</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>To the observer, the appearance of an open cluster can vary quite substantially. Sometimes only a few stars are visible for some clusters and sometimes there are so many stars in a cluster, they blend into a blur. Often the observing instrument has much to do with how a cluster appears. Some clusters in binoculars or very small <ins class="diffchange diffchange-inline">[[telescope|</ins>telescopes<ins class="diffchange diffchange-inline">]] </ins>appear as a faint fuzzy patch which, when observed through a larger telescope, resolve into individual stars, [[M37]] for example. Other clusters just look like a group of stars in the same point in the sky regardless of the instrument used. It is notable that two quite well known open clusters, [[Hyades |</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>The Hyades]] and [[M45 | The Pleiades]] are naked eye clusters that are visible even from inside a city and that observation with binoculars or a telescope don't do much more than reveal more stars in these two clusters.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>The Hyades]] and [[M45 | The Pleiades]] are naked eye clusters that are visible even from inside a city and that observation with binoculars or a telescope don't do much more than reveal more stars in these two clusters.</div></td></tr>
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</table>Evilscientisthttp://www.citydeepsky.com/wiki/index.php?title=Open_cluster&diff=2417&oldid=prevEvilscientist at 20:36, 9 February 20092009-02-09T20:36:45Z<p></p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>So the [[M44|Beehive Cluster]] is rated at I2r and the more spread out [[M45|Pleiades]] at II3r<ref name="trumpler"> </ref>.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>So the [[M44|Beehive Cluster]] is rated at I2r and the more spread out [[M45|Pleiades]] at II3r<ref name="trumpler"> </ref>.</div></td></tr>
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<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>[[Category:Astronomical]]  </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>[[Category:Astronomical <ins class="diffchange diffchange-inline">object</ins>]]  </div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>==References==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>==References==</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div><references/></div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div><references/></div></td></tr>
</table>Evilscientisthttp://www.citydeepsky.com/wiki/index.php?title=Open_cluster&diff=1831&oldid=prevEvilscientist at 18:37, 22 January 20092009-01-22T18:37:42Z<p></p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|}</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|}</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>So the [[M44|Beehive Cluster]] is rated at I2r and the more spread out [[M45|Pleiades]] at II3r<ref name="trumpler"></ref>.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>So the [[M44|Beehive Cluster]] is rated at I2r and the more spread out [[M45|Pleiades]] at II3r<ref name="trumpler"> </ref>.</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Category:Astronomical]]  </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Category:Astronomical]]  </div></td></tr>
</table>Evilscientisthttp://www.citydeepsky.com/wiki/index.php?title=Open_cluster&diff=1830&oldid=prevEvilscientist at 18:36, 22 January 20092009-01-22T18:36:57Z<p></p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|}</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|}</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>So the [[M44|Beehive Cluster]] is rated at I2r and the more spread out [[M45|Pleiades]] at II3r.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>So the [[M44|Beehive Cluster]] is rated at I2r and the more spread out [[M45|Pleiades]] at II3r<ins class="diffchange diffchange-inline"><ref name="trumpler"></ref></ins>.</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Category:Astronomical]]  </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Category:Astronomical]]  </div></td></tr>
</table>Evilscientisthttp://www.citydeepsky.com/wiki/index.php?title=Open_cluster&diff=1829&oldid=prevEvilscientist: Correct Trumpler Classification, change reference.2009-01-22T18:36:07Z<p>Correct Trumpler Classification, change reference.</p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>===Trumpler system===</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>===Trumpler system===</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>To avoid confusion in terminology, a system of categorizing the appearance of open clusters was developed by the Swiss-American astronomer Robert Trumpler<ref name="<del class="diffchange diffchange-inline">trumpler</del>">Weaver, Harold; Weaver, Paul, ''Robert Julius Trumpler, 1886-1956'', <u>Publications of the Astronomical Society of the Pacific</u>, Vol. 69, No. 409, p.304</ref> developed a system of classification for open clusters that is much more precise than the general terms used above.  </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>To avoid confusion in terminology, a system of categorizing the appearance of open clusters was developed by the Swiss-American astronomer Robert Trumpler<ref name="<ins class="diffchange diffchange-inline">weaver</ins>">Weaver, Harold; Weaver, Paul, ''Robert Julius Trumpler, 1886-1956'', <u>Publications of the Astronomical Society of the Pacific</u>, Vol. 69, No. 409, p.304</ref> developed a system of classification for open clusters that is much more precise than the general terms used above.  </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>The Trumpler system uses three terms to describe an open cluster. Term 1 gives an indication of the concentration of stars (how dense). Term 2 gives information on the range in brightness of the individual stars and term 3 provides information on the richness or number of stars. The table below<ref name="<del class="diffchange diffchange-inline">dyer</del>"><del class="diffchange diffchange-inline">Dickenson</del>, <del class="diffchange diffchange-inline">Terrence and Dyer</del>, <del class="diffchange diffchange-inline">Allan</del>, <u><del class="diffchange diffchange-inline">The Backyard Astronomer's Guide</del></u> <del class="diffchange diffchange-inline">Rev. Ed</del>.</ref> provides a definition of each term.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>The Trumpler system uses three terms to describe an open cluster. Term 1 gives an indication of the concentration of stars (how dense). Term 2 gives information on the range in brightness of the individual stars and term 3 provides information on the richness or number of stars. The table below<ref name="<ins class="diffchange diffchange-inline">trumpler</ins>"><ins class="diffchange diffchange-inline">Trumpler</ins>, <ins class="diffchange diffchange-inline">Robert J.</ins>, <ins class="diffchange diffchange-inline">''Preliminary Results on the Distances, Dimensions and Space Distribution of Open Star Clusters''</ins>, <u><ins class="diffchange diffchange-inline">Lick Observatory Bulletin</ins></u><ins class="diffchange diffchange-inline">, Vol XIV, No</ins>. <ins class="diffchange diffchange-inline">420, pp 154-188</ins></ref> provides a definition of each term.</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>{| cellspacing="0" border="1"</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>{| cellspacing="0" border="1"</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|III</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|III</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|well separated from surrounding stars, with no concentration to the centre</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|well separated from surrounding stars, with no concentration to the centre</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">|IV</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">|Not well separated from surrounding stars with stars slowly passing into the surrounding stars and appearing like a star field condensation</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|-</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|-</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>| style="background:#eaeaea" colspan="2" | '''Range in Brightness'''</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>| style="background:#eaeaea" colspan="2" | '''Range in Brightness'''</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|m</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|m</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>|<del class="diffchange diffchange-inline">medium </del>rich clusters with between 50 and 100 stars</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>|<ins class="diffchange diffchange-inline">moderately </ins>rich clusters with between 50 and 100 stars</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|r</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|r</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>So the <del class="diffchange diffchange-inline">Pleiades are </del>rated at <del class="diffchange diffchange-inline">I3r </del>and the more spread out <del class="diffchange diffchange-inline">Hyades </del>at <del class="diffchange diffchange-inline">II3m</del>.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>So the <ins class="diffchange diffchange-inline">[[M44|Beehive Cluster]] is </ins>rated at <ins class="diffchange diffchange-inline">I2r </ins>and the more spread out <ins class="diffchange diffchange-inline">[[M45|Pleiades]] </ins>at <ins class="diffchange diffchange-inline">II3r</ins>.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Category:Astronomical]]  </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Category:Astronomical]]  </div></td></tr>
</table>Evilscientisthttp://www.citydeepsky.com/wiki/index.php?title=Open_cluster&diff=1696&oldid=prevEvilscientist at 05:46, 21 January 20092009-01-21T05:46:51Z<p></p>
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<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>[[<del class="diffchange diffchange-inline">image</del>:M45.jpg |thumb ]]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>[[<ins class="diffchange diffchange-inline">Image</ins>:M45.jpg<ins class="diffchange diffchange-inline">|float</ins>|thumb<ins class="diffchange diffchange-inline">|250px|Pleiades</ins>]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Open star clusters are groups of stars without a defined shape and generally only have a few hundred members. These groupings are loosely held together by their mutual gravitation and have a common age and origin<ref name="Abell">Abell, George O, <u>Exploration of the Universe</u>, 4th ed</ref>. This makes them very useful to astronomy as this has given science much insight into stellar evolution by looking at various open clusters of differing ages. This eventually lead to the ability to determine the age of star clusters to some accuracy<ref name="freedman">Freedman, Roger A. and Kaufmann III, William J., <u>Universe</u>, 8th ed.</ref>. As open clusters are only weakly bound gravitationally, they eventually disperse as they orbit the galaxy due to interactions with other stars.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Open star clusters are groups of stars without a defined shape and generally only have a few hundred members. These groupings are loosely held together by their mutual gravitation and have a common age and origin<ref name="Abell">Abell, George O, <u>Exploration of the Universe</u>, 4th ed</ref>. This makes them very useful to astronomy as this has given science much insight into stellar evolution by looking at various open clusters of differing ages. This eventually lead to the ability to determine the age of star clusters to some accuracy<ref name="freedman">Freedman, Roger A. and Kaufmann III, William J., <u>Universe</u>, 8th ed.</ref>. As open clusters are only weakly bound gravitationally, they eventually disperse as they orbit the galaxy due to interactions with other stars.</div></td></tr>
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</table>Evilscientisthttp://www.citydeepsky.com/wiki/index.php?title=Open_cluster&diff=1695&oldid=prevEvilscientist: add image, delete category open cluster.2009-01-21T05:39:54Z<p>add image, delete category open cluster.</p>
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<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">[[image:M45.jpg |thumb ]]</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Open star clusters are groups of stars without a defined shape and generally only have a few hundred members. These groupings are loosely held together by their mutual gravitation and have a common age and origin<ref name="Abell">Abell, George O, <u>Exploration of the Universe</u>, 4th ed</ref>. This makes them very useful to astronomy as this has given science much insight into stellar evolution by looking at various open clusters of differing ages. This eventually lead to the ability to determine the age of star clusters to some accuracy<ref name="freedman">Freedman, Roger A. and Kaufmann III, William J., <u>Universe</u>, 8th ed.</ref>. As open clusters are only weakly bound gravitationally, they eventually disperse as they orbit the galaxy due to interactions with other stars.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Open star clusters are groups of stars without a defined shape and generally only have a few hundred members. These groupings are loosely held together by their mutual gravitation and have a common age and origin<ref name="Abell">Abell, George O, <u>Exploration of the Universe</u>, 4th ed</ref>. This makes them very useful to astronomy as this has given science much insight into stellar evolution by looking at various open clusters of differing ages. This eventually lead to the ability to determine the age of star clusters to some accuracy<ref name="freedman">Freedman, Roger A. and Kaufmann III, William J., <u>Universe</u>, 8th ed.</ref>. As open clusters are only weakly bound gravitationally, they eventually disperse as they orbit the galaxy due to interactions with other stars.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>So the Pleiades are rated at I3r and the more spread out Hyades at II3m.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>So the Pleiades are rated at I3r and the more spread out Hyades at II3m.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>[[Category:Astronomical<del class="diffchange diffchange-inline">]] [[Category:Open Cluster</del>]]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>[[Category:Astronomical]]  </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>==References==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>==References==</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div><references/></div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div><references/></div></td></tr>
</table>Evilscientisthttp://www.citydeepsky.com/wiki/index.php?title=Open_cluster&diff=1693&oldid=prevEvilscientist at 05:12, 21 January 20092009-01-21T05:12:55Z<p></p>
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<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del class="diffchange diffchange-inline">An open cluster is a group </del>of stars <del class="diffchange diffchange-inline">that </del>are together <del class="diffchange diffchange-inline">in the sky </del>and have a common origin<del class="diffchange diffchange-inline">. The cluster may be tight (stars close together) or loose (stars far apart)</del>, <del class="diffchange diffchange-inline">sparse (not a lot </del>of <del class="diffchange diffchange-inline">stars) or dense (a lot </del>of stars<del class="diffchange diffchange-inline">)</del>.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">Open star clusters are groups </ins>of stars <ins class="diffchange diffchange-inline">without a defined shape and generally only have a few hundred members. These groupings </ins>are <ins class="diffchange diffchange-inline">loosely held </ins>together <ins class="diffchange diffchange-inline">by their mutual gravitation </ins>and have a common <ins class="diffchange diffchange-inline">age and </ins>origin<ins class="diffchange diffchange-inline"><ref name="Abell">Abell</ins>, <ins class="diffchange diffchange-inline">George O, <u>Exploration </ins>of <ins class="diffchange diffchange-inline">the Universe</u>, 4th ed</ref>. This makes them very useful to astronomy as this has given science much insight into stellar evolution by looking at various open clusters </ins>of <ins class="diffchange diffchange-inline">differing ages. This eventually lead to the ability to determine the age of star clusters to some accuracy<ref name="freedman">Freedman, Roger A. and Kaufmann III, William J., <u>Universe</u>, 8th ed.</ref>. As open clusters are only weakly bound gravitationally, they eventually disperse as they orbit the galaxy due to interactions with other </ins>stars.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">To the observer, the appearance of an open cluster can vary quite substantially. Sometimes only a few stars are visible for some clusters and sometimes there are so many stars in a cluster, they blend into a blur. Often the observing instrument has much to do with how a cluster appears. Some clusters in binoculars or very small telescopes appear as a faint fuzzy patch which, when observed through a larger telescope, resolve into individual stars, [[M37]] for example. Other clusters just look like a group of stars in the same point in the sky regardless of the instrument used. It is notable that two quite well known open clusters, [[Hyades |</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">The Hyades]] and [[M45 | The Pleiades]] are naked eye clusters that are visible even from inside a city and that observation with binoculars or a telescope don't do much more than reveal more stars in these two clusters.</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="background: #ffa; color:black; font-size: smaller;"><div>[[Category:Astronomical]][[Category:Open Cluster]]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">==Classifying open clusters==</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">===General terms===</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">Since the appearance of open clusters can vary so widely from cluster to cluster, many terms have been used to describe them. In terms of the number of members, terms such as sparse or poor are used to describe clusters with few members. On the other hand rich clusters have many members. Dense clusters have most of their members close together whereas the term sparse can also be used for clusters that are widely dispersed.</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div> </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">===Trumpler system===</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">To avoid confusion in terminology, a system of categorizing the appearance of open clusters was developed by the Swiss-American astronomer Robert Trumpler<ref name="trumpler">Weaver, Harold; Weaver, Paul, ''Robert Julius Trumpler, 1886-1956'', <u>Publications of the Astronomical Society of the Pacific</u>, Vol. 69, No. 409, p.304</ref> developed a system of classification for open clusters that is much more precise than the general terms used above. </ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div> </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">The Trumpler system uses three terms to describe an open cluster. Term 1 gives an indication of the concentration of stars (how dense). Term 2 gives information on the range in brightness of the individual stars and term 3 provides information on the richness or number of stars. The table below<ref name="dyer">Dickenson, Terrence and Dyer, Allan, <u>The Backyard Astronomer's Guide</u> Rev. Ed.</ref> provides a definition of each term.</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div> </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">{| cellspacing="0" border="1"</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|style="background:#eaeaea"  colspan="2"|'''Concentration of Stars'''</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|I</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|well separated from surrounding stars, with a strong concentration to the centre</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|II</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|well separated from surrounding stars, with little concentration to the centre</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|III</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|well separated from surrounding stars, with no concentration to the centre</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">| style="background:#eaeaea" colspan="2" | '''Range in Brightness'''</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|1</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|small range in brightness</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|2</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|moderate range in brightness</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|3</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|large range in brightness</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">| style="background:#eaeaea" colspan="2" |'''Number of Stars'''</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|p</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|poor clusters with less than 50 stars</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|m</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|medium rich clusters with between 50 and 100 stars</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|-</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|r</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">| rich clusters with over 100 stars</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">|}</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div> </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">So the Pleiades are rated at I3r and the more spread out Hyades at II3m.</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div> </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>[[Category:Astronomical]] [[Category:Open Cluster]]</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div> </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">==References==</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline"><references/></ins></div></td></tr>
</table>Evilscientisthttp://www.citydeepsky.com/wiki/index.php?title=Open_cluster&diff=1495&oldid=prevEvilscientist at 23:46, 14 January 20092009-01-14T23:46:04Z<p></p>
<p><b>New page</b></p><div>An open cluster is a group of stars that are together in the sky and have a common origin. The cluster may be tight (stars close together) or loose (stars far apart), sparse (not a lot of stars) or dense (a lot of stars).<br />
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[[Category:Astronomical]][[Category:Open Cluster]]</div>Evilscientist