{"id":11759,"date":"2011-07-21T00:13:58","date_gmt":"2011-07-21T00:13:58","guid":{"rendered":"http:\/\/www.bitacoradegalileo.com\/en\/?p=11759"},"modified":"2011-07-21T18:35:24","modified_gmt":"2011-07-21T18:35:24","slug":"the-pleiades-open-cluster","status":"publish","type":"post","link":"http:\/\/www.bitacoradegalileo.com\/en\/2011\/07\/21\/the-pleiades-open-cluster\/","title":{"rendered":"The Pleiades open cluster"},"content":{"rendered":"

\"\"<\/a><\/p>\n

WHAT ARE\u00a0OPEN\u00a0CLUSTERS?<\/strong><\/p>\n

Open clusters\u00a0are groups of\u00a0tens, hundreds\u00a0or thousands of\"\"<\/a> stars\u00a0originated in\u00a0the same cloud of\u00a0gas.\u00a0Often the\u00a0gas\u00a0is gone,\u00a0in whole or in\u00a0part, because\u00a0the radiation emitted by\u00a0the brightest stars\u00a0and his appearance\u00a0is that of an\u00a0irregular\u00a0splash\u00a0of\u00a0bright\u00a0spots, with no\u00a0general\u00a0structure and\u00a0asymmetric.
\n\"\"<\/a>
\nThe\u00a0hosted stars\u00a0are generally young\u00a0(a few hundred\u00a0million years;\u00a0compare with\u00a0the 4,000\u00a0million\u00a0of the Sun), massive and\u00a0very hot.
\nThey are\u00a0scattered on\u00a0sizes\u00a0in the order of\u00a0thirty\u00a0light-years,\u00a0and\u00a0are slowly\u00a0dispersed\u00a0by the\u00a0tidal effect\u00a0produced by\u00a0the center of the\u00a0Milky Way,\"\"<\/a>so that\u00a0over time,\u00a0-millions of years- the stars\u00a0that form it\u00a0will\u00a0be\u00a0mixing\u00a0with the rest\u00a0of the galaxy.\u00a0Open clusters\u00a0are also known\u00a0by the name of\u00a0galaxy clusters.
\nWe bring\u00a0here, as\u00a0prominent\u00a0examples, from top\u00a0to bottom\u00a0in this order, the\u00a0Ptolemy’s\u00a0Cluster<\/strong>\u00a0in the constellation\u00a0Scorpio<\/strong>, the spectacular\u00a0double cluster\u00a0in Perseus\u00a0<\/strong>and\u00a0the Manger\u00a0<\/strong>(Praesepe\u00a0<\/strong>in Latin),\u00a0or\u00a0the Beehive\u00a0Cluster<\/strong>\u00a0in Cancer<\/strong>.
\nBut today\u00a0we will focus on\u00a0the beautiful\u00a0Pleiades star cluster\u00a0in the constellation\u00a0of Taurus, which\u00a0is undoubtedly the\u00a0most famous, brilliant\u00a0and beautiful\u00a0of them all.<\/p>\n

THE PLEIADES\u00a0ARE IN\u00a0TAURUS<\/strong><\/p>\n

<\/strong>\"Taurus\"<\/a>Taurus<\/strong>\u00a0is\u00a0the\u00a0Zodiac\u00a0<\/strong>constellation\u00a0invented by\u00a0the ancient Babylonians,\u00a0whose Latin name\u00a0(Taurus<\/em>) means\u00a0bull.\u00a0Stands out\u00a0in thewinter\u00a0sky,\u00a0between\u00a0Aries\u00a0<\/strong>to the west and\u00a0Gemini\u00a0<\/strong>to the east,\u00a0its predecessor and\u00a0successor in the\u00a0Zodiac,\u00a0respectively.\u00a0To the north are\u00a0Perseus\u00a0<\/strong>and\u00a0Auriga<\/strong>,\u00a0Orion<\/strong>‘s\u00a0southeast\u00a0and\u00a0to the southwest\u00a0the constellation\u00a0Eridanus\u00a0river\u00a0<\/strong>and\u00a0Cetus<\/strong>, the Whale.<\/p>\n

\"\"<\/a>
\nIn this picture\u00a0we see the\u00a0night sky\u00a0in the city of\u00a0Buenos\u00a0Aires<\/strong> (34\u00a0\u00ba\u00a0S\u00a0latitude,\u00a0the same as\u00a0Cape Town,\u00a0South Africa),\u00a0in the morning twilight\u00a0of\u00a0June 30th.\u00a0All\u00a0the stars that\u00a0appear are in\u00a0the\u00a0ortho,\u00a0ie,\u00a0emerging from\u00a0the\u00a0eastern horizon, and\u00a0their way to their transition\u00a0to the north.\u00a0Hamal<\/strong>, the main\u00a0star of\u00a0Aries<\/strong>,\u00a0is the\u00a0highest,\u00a0while\u00a0Gemini\u00a0<\/strong>is still\u00a0below the horizon.\u00a0The inhabitants of the Northern Hemisphere\u00a0will notice\u00a0the position\u00a0of Orion<\/strong>,\u00a0just the opposite\u00a0of how\u00a0they normaly\u00a0see it\u00a0in their\u00a0usual\u00a0latitudes, as the stars representing the\u00a0feet of the giant\u00a0hunter,\u00a0Rigel<\/strong> and\u00a0Saiph\u00a0<\/strong>are those which\u00a0are\u00a0higher, while\u00a0Sirius<\/strong> and\u00a0Aldebaran\u00a0<\/strong>are at opposite\u00a0positions\u00a0as they are seen\u00a0by the\u00a0boreals.\u00a0The Moon<\/strong>\u00a0is in conjunction with\u00a0the Pleiades<\/strong>,\u00a0no\u00a0strange\u00a0thing, as will see.
\nThe\u00a0principal star\u00a0of this constellation\u00a0is Aldebaran\u00a0<\/strong>(Alpha\u00a0Tauri),\"\"<\/a>a\u00a0red-orange\u00a0giant\u00a0of magnitude\u00a0+0.87,\u00a0which is the thirteenth\u00a0brightest\u00a0from around the\u00a0night sky,\u00a0El Nath<\/strong>\u00a0(Beta\u00a0Tauri) or Al\u00a0Nathis a\u00a0blue-white\u00a0giant\u00a0of magnitude\u00a0+1.68.\u00a0In this constellation\u00a0are famous,\u00a0as well as\u00a0the Pleiades<\/strong>, the\u00a0Crab Nebula<\/strong> (M1<\/strong>),\u00a0that we see\u00a0on the right, and\u00a0the Hyades<\/strong>, another\u00a0open cluster in\u00a0the same\u00a0line of sight of\u00a0Aldebaran<\/strong>,\u00a0but\u00a0this star\u00a0is not part\u00a0of the cluster,because\u00a0it is located\u00a0halfway.<\/p>\n

The open cluster of\u00a0the Pleiades (M45)<\/strong><\/p>\n

The\u00a0Pleiades\u00a0<\/strong>(Pigeons\u00a0in Greek),\u00a0is an object\u00a0visible\u00a0without optical aid, located\u00a0at the side of\u00a0the constellation\u00a0Taurus<\/strong>.\u00a0Receivesalso the name of\u00a0Messier\u00a045<\/strong> or\u00a0M45<\/strong>,\u00a0as Charles\u00a0Messier\u00a0included it\u00a0correspondingly numbered\u00a0in his catalogue of\u00a0disturbing objects\u00a0in 1769.\u00a0Other names that\u00a0have been\u00a0popular tradition\u00a0are\u00a0The<\/strong> Seven Sisters<\/strong>\u00a0or\u00a0The\u00a0seven goats<\/strong>.<\/p>\n

This is a\u00a0group of stars,\u00a0a total of approximately\u00a0500,\u00a0very young (about 100 million\u00a0years), which\u00a0is located approximately\u00a0400 light-years\u00a0away,\u00a0this figure\u00a0oscillates\u00a0depending on\u00a0the sources consulted.\"\"<\/a>The cluster\u00a0is about 12\u00a0light years\u00a0in diameter, and\u00a0occupies\u00a0an angle of\u00a0about 110\u00a0minutes of arc in\u00a0the sky, equivalent\u00a0to nearly four times\u00a0the Full Moon<\/strong>,\u00a0\"\"<\/a>starring\u00a0frequent\u00a0conjunctions\u00a0with it, as shown\u00a0on the left,\u00a0as well as\u00a0with the\u00a0other planets in the\u00a0Solar System,\u00a0because it is located at\u00a0is only 5\u00a0\u00b0\u00a0from the ecliptic\u00a0<\/strong>(the line\u00a0describing the\u00a0moon and\u00a0all planets\u00a0in its orbit). \"\"<\/a>This circumstance\u00a0produces\u00a0beautiful\u00a0effects\u00a0of rapprochement between\u00a0the stars, which\u00a0are\u00a0used by\u00a0enthusiasts ofastrophotography.\u00a0To the right\u00a0the Pleaides<\/strong>\u00a0are in conjunction with\u00a0Venus<\/strong>.
\nThe brightest stars in the cluster are blue-white color and have a size equivalent to five times the Sun.<\/p>\n

\"\"<\/p>\n

The principal stars are\u00a0Alcyone<\/strong> (magnitude 2.87), Atlas<\/strong> (3.63), Electra<\/strong> (3.7), Maia<\/strong> (3.87), Merope <\/strong>(4.18), Taygeta <\/strong>(4.3), Pleione<\/strong> (5.09), Celaeno<\/strong> (5.46), Tau 18 <\/strong>(5.64), Asterope I <\/strong>(5.76) and Asterope II <\/strong>(6.43).<\/p>\n

The cluster is\u00a0surrounded by\u00a0a nebula, which\u00a0becomes more evident\u00a0in the proximity of\u00a0the brightest stars, and reaches its greatest prominence\u00a0wrapping\u00a0Merope, a fact which\u00a0has important\u00a0consequences in the\u00a0mythology\u00a0around this\u00a0beautiful\u00a0cluster,\u00a0as we will see.\u00a0The cluster stars\u00a0split\u00a0gradually, and\u00a0it is estimated that\u00a0within 250\u00a0millions of years\u00a0will not exist\u00a0as such, separating and becoming\u00a0individual stars\u00a0(or multiple\u00a0if applicable).<\/p>\n

HISTORY\u00a0AND MYTHOLOGY<\/strong><\/p>\n

The Pleiades<\/strong>\u00a0are mentioned in the\u00a0Mahabharata<\/strong>,\u00a0the Iliad\u00a0<\/strong>and the Odyssey\u00a0<\/strong>of Homer, and\u00a0three times in\u00a0the Bible<\/strong>.\u00a0They form the basis\u00a0of the Mayan calendar<\/strong>, to\u00a0whose tradition\u00a0they are\u00a0400 warriors\u00a0whose souls\u00a0were put into\u00a0the sky\u00a0after being\u00a0killed by\u00a0the arrogant\u00a0Zipacna<\/strong>.<\/p>\n

\"\"<\/a>For the\u00a0classical\u00a0Hellenistic\u00a0tradition,\u00a0the Pleiades<\/strong>\u00a0are\u00a0the seven daughters of\u00a0Atlas\u00a0<\/strong>and\u00a0Pleione<\/strong>, sisters\u00a0among others\u00a0of the\u00a0Hyades\u00a0<\/strong>which, after being\u00a0persecuted\u00a0for years\u00a0by the giant\u00a0Orion<\/strong>,\u00a0appealed for help to\u00a0Zeus<\/strong>, who\u00a0turned them into\u00a0pigeons,\u00a0after which they\u00a0rested\u00a0on the back\u00a0of the Bull\u00a0(Taurus\u00a0<\/strong>constellation), which\u00a0thus constituted\u00a0the guardian\u00a0of the sisters.\u00a0Merope<\/strong>, embarrassed\u00a0after being raped by\u00a0the giant,\u00a0is hidden behind\u00a0its own\u00a0nebula.<\/p>\n","protected":false},"excerpt":{"rendered":"

WHAT ARE\u00a0OPEN\u00a0CLUSTERS? Open clusters\u00a0are groups of\u00a0tens, hundreds\u00a0or thousands of stars\u00a0originated in\u00a0the same cloud of\u00a0gas.\u00a0Often the\u00a0gas\u00a0is gone,\u00a0in whole or in\u00a0part, because\u00a0the radiation emitted by\u00a0the brightest stars\u00a0and his appearance\u00a0is that of an\u00a0irregular\u00a0splash\u00a0of\u00a0bright\u00a0spots, with no\u00a0general\u00a0structure and\u00a0asymmetric. The\u00a0hosted stars\u00a0are generally young\u00a0(a few hundred\u00a0million years;\u00a0compare with\u00a0the 4,000\u00a0million\u00a0of the Sun), massive and\u00a0very hot. They are\u00a0scattered on\u00a0sizes\u00a0in the order of\u00a0thirty\u00a0light-years,\u00a0and\u00a0are slowly\u00a0dispersed\u00a0by the\u00a0tidal […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28],"tags":[25,27,33,35,37,36],"class_list":["post-11759","post","type-post","status-publish","format-standard","hentry","category-deep-sky","tag-conjunctions","tag-messier-objects-2","tag-moon","tag-mythology","tag-nebulae","tag-open-clusters"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"http:\/\/www.bitacoradegalileo.com\/en\/wp-json\/wp\/v2\/posts\/11759","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.bitacoradegalileo.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.bitacoradegalileo.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.bitacoradegalileo.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/www.bitacoradegalileo.com\/en\/wp-json\/wp\/v2\/comments?post=11759"}],"version-history":[{"count":10,"href":"http:\/\/www.bitacoradegalileo.com\/en\/wp-json\/wp\/v2\/posts\/11759\/revisions"}],"predecessor-version":[{"id":11823,"href":"http:\/\/www.bitacoradegalileo.com\/en\/wp-json\/wp\/v2\/posts\/11759\/revisions\/11823"}],"wp:attachment":[{"href":"http:\/\/www.bitacoradegalileo.com\/en\/wp-json\/wp\/v2\/media?parent=11759"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.bitacoradegalileo.com\/en\/wp-json\/wp\/v2\/categories?post=11759"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.bitacoradegalileo.com\/en\/wp-json\/wp\/v2\/tags?post=11759"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}