Messier 93

<h2 id="observational-history-and-appearance">Observational history and appearance</h2>
It was discovered by <a href="/facts/Charles_Messier/dTokW7Yy">Charles Messier</a> then added to his catalogue of <a href="/facts/Comet/w34utQCd">comet</a>-like objects in 1781.<a class="footnote-ref" id="fnref:1" href="#fn:1">1</a><a class="footnote-ref" id="fnref:2" href="#fn:2">2</a> <a href="/facts/Caroline_Herschel/b0jouFmG">Caroline Herschel</a>, the younger sister of <a href="/facts/William_Herschel/SsruaBvq">William Herschel</a>, independently discovered it in 1783, thinking it had not yet been catalogued by Messier.<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a> 
<a href="/facts/Walter_Scott_Houston/fWtmzqEx">Walter Scott Houston</a> (died 1993) described its appearance:<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a>

<blockquote>Some observers mention the cluster as having the shape of a starfish. With a fair-sized telescope, this is its appearance on a dull night, but [a four-inch refractor] shows it as a typical star-studded galactic cluster.</blockquote>
<h2 id="properties">Properties</h2>
It has a <a href="/facts/Trumpler_class/UodlJqcx">Trumpler class</a> of I 3 r, indicating it is strongly concentrated (I) with a large range in brightness (3) and is rich in stars (r).<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a>
M93 is about 3,380<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a> <a href="/facts/Light-year/IGc5NdQb">light-years</a> from the <a href="/facts/Solar_radius/5t1Xavju">solar radius</a> and has a great spatial radius of 10 light-years,<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> a <a href="/facts/Globular_cluster/FL0EERJU">tidal radius</a> of 13.1±2.3 ly,<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a> and a core radius of 4.2 ly.<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> Its age is estimated at 387.3 million years.<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a> It is nearly on the <a href="/facts/Galactic_plane/4eaqfCIB">galactic plane</a> and has an orbit that varies between 28–29 kly (8.5–8.9 kpc) from the <a href="/facts/Galactic_Center/TI4MwWwM">Galactic Center</a> over a period of 242.7±7.9 Myr.<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a>
Fifty-four <a href="/facts/Variable_star/Ac8mp2gy">variable stars</a> have been found in M93, including one <a href="/facts/Slowly_pulsating_B-type_star/XgJNLE9R">slowly pulsating B-type star</a>, one <a href="/facts/Rotating_ellipsoidal_variable/kkYVyL0C">rotating ellipsoidal variable</a>, seven <a href="/facts/Delta_Scuti_variable/EQtxUC4z">Delta Scuti variables</a>, six <a href="/facts/Gamma_Doradus_variable/IFDQBKpo">Gamma Doradus variables</a>, and one hybrid δ<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a> Sct/γ Dor<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a> pulsator.<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a> Four <a href="/facts/Spectroscopic_binary/TYlDe1bD">spectroscopic binary</a> systems within include a <a href="/facts/Yellow_straggler/jadb4Tmx">yellow straggler</a> component.<a class="footnote-ref" id="fnref:15" href="#fn:15">15</a>

<h2 id="gallery">Gallery</h2>

<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/List_of_Messier_objects/YKz2MxzQ">List of Messier objects</a></li></ul>

<h2 id="external-links">External links</h2>

Wikimedia Commons has media related to Messier 93.

<ul><li><a href="http://messier.seds.org/m/m093.html">SEDS: Open Star Cluster M93</a></li>
<li></li>
<li>Messier 93 on <a href="/facts/WikiSky/P0lUw52f">WikiSky</a>: <a href="http://www.wikisky.org/?object=Messier+93&img_source=DSS2">DSS2</a>, <a href="http://www.wikisky.org/?object=Messier+93&img_source=SDSS">SDSS</a>, <a href="http://www.wikisky.org/?object=Messier+93&img_source=GALEX">GALEX</a>, <a href="http://www.wikisky.org/?object=Messier+93&img_source=IRAS">IRAS</a>, <a href="http://www.wikisky.org/?object=Messier+93&img_source=HALPHA">Hydrogen α</a>, <a href="http://www.wikisky.org/?object=Messier+93&img_source=RASS">X-Ray</a>, <a href="http://www.wikisky.org/?object=Messier+93&img_source=IMG_all">Astrophoto</a>, <a href="http://www.wikisky.org/?object=Messier+93">Sky Map</a>, <a href="http://www.wikisky.org/starview?object=Messier+93">Articles and images</a></li>
<li>Gray, Meghan; <a href="/facts/John_Zarnecki/eC7LGMkC">Zarnecki, John</a>. <a href="http://www.deepskyvideos.com/videos/messier/M93_open_cluster.html">"M93 – Open Cluster"</a>. Deep Sky Videos. <a href="/facts/Brady_Haran/7oNb0Tez">Brady Haran</a>. Retrieved 2018-12-05.</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">On March 20 <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Frommert, Hartmut; Kronberg, Christine (September 2, 2007), "Messier 93", SEDS Messier pages, Students for the Exploration and Development of Space (SEDS), retrieved 2018-12-07. <a href="http://www.messier.seds.org/m/m093.html" target="_blank">http://www.messier.seds.org/m/m093.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Hoskin, Michael (February 1, 2016), "Gazing at the starry heavens", Astronomy & Geophysics, 57 (1): 1.22 – 1.25, Bibcode:2016A&G....57a1.22H, doi:10.1093/astrogeo/atw038 <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Houston, Walter Scott (2005). Deep-Sky Wonders. Sky Publishing Corporation. ISBN 978-1-931559-23-2. <a href="978-1-931559-23-2" target="_blank">978-1-931559-23-2</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Maitzen, H. M. (November 1993), "Photoelectric Search for Peculiar Stars in Open Clusters - Part Fourteen - NGC1901 NGC2169 NGC2343 CR:132 NGC2423 and NGC2447", Astronomy and Astrophysics Supplement, 102 (1): 1, Bibcode:1993A&AS..102....1M. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Wu, Zhen-Yu; et al. (November 2009), "The orbits of open clusters in the Galaxy", Monthly Notices of the Royal Astronomical Society, 399 (4): 2146–2164, arXiv:0909.3737, Bibcode:2009MNRAS.399.2146W, doi:10.1111/j.1365-2966.2009.15416.x, S2CID 6066790. <a href="/wiki/Monthly_Notices_of_the_Royal_Astronomical_Society" target="_blank">/wiki/Monthly_Notices_of_the_Royal_Astronomical_Society</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Finlay, Warren H. (2014), Concise Catalog of Deep-Sky Objects: Astrophysical Information for 550 Galaxies, Clusters and Nebulae, The Patrick Moore Practical Astronomy Series (2nd ed.), Springer, p. 120, Bibcode:2014ccds.book.....F, ISBN 978-3319031705 <a href="978-3319031705" target="_blank">978-3319031705</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Piskunov, A. E.; et al. (January 2008), "Tidal radii and masses of open clusters", Astronomy and Astrophysics, 477 (1): 165–172, Bibcode:2008A&A...477..165P, doi:10.1051/0004-6361:20078525. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Piskunov, A. E.; et al. (June 2007), "Towards absolute scales for the radii and masses of open clusters", Astronomy and Astrophysics, 468 (1): 151–161, arXiv:astro-ph/0702517, Bibcode:2007A&A...468..151P, doi:10.1051/0004-6361:20077073, S2CID 14769639. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Wu, Zhen-Yu; et al. (November 2009), "The orbits of open clusters in the Galaxy", Monthly Notices of the Royal Astronomical Society, 399 (4): 2146–2164, arXiv:0909.3737, Bibcode:2009MNRAS.399.2146W, doi:10.1111/j.1365-2966.2009.15416.x, S2CID 6066790. <a href="/wiki/Monthly_Notices_of_the_Royal_Astronomical_Society" target="_blank">/wiki/Monthly_Notices_of_the_Royal_Astronomical_Society</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Wu, Zhen-Yu; et al. (November 2009), "The orbits of open clusters in the Galaxy", Monthly Notices of the Royal Astronomical Society, 399 (4): 2146–2164, arXiv:0909.3737, Bibcode:2009MNRAS.399.2146W, doi:10.1111/j.1365-2966.2009.15416.x, S2CID 6066790. <a href="/wiki/Monthly_Notices_of_the_Royal_Astronomical_Society" target="_blank">/wiki/Monthly_Notices_of_the_Royal_Astronomical_Society</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">Delta Scuti <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">Gamma Doradus <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
<li id="fn:14">Eyer, L.; Eggenberger, P.; Greco, C.; Saesen, S.; Anderson, R. I.; Mowlavi, N. (September 2010), "Time resolved surveys of stellar clusters", JENAM 2010, Joint European and National Astronomy Meeting held 6-10 September, 2010 in Lisbon Portugal, p. 212, arXiv:1011.4952, Bibcode:2010jena.confE.212E, 212. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></li>
<li id="fn:15">da Silveira, M. D.; et al. (June 2018), "Red giants and yellow stragglers in the young open cluster NGC 2447", Monthly Notices of the Royal Astronomical Society, 476 (4): 4907–4931, Bibcode:2018MNRAS.476.4907D, doi:10.1093/mnras/sty265 <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></li>
</ol>

Messier 93 open-in-new

Messier 93