{"id":581,"date":"2008-08-21T00:11:33","date_gmt":"2008-08-21T05:11:33","guid":{"rendered":"http:\/\/arxivblog.com\/?p=581"},"modified":"2008-08-21T00:11:50","modified_gmt":"2008-08-21T05:11:50","slug":"the-black-hole-at-the-center-of-our-galaxy","status":"publish","type":"post","link":"http:\/\/arxivblog.com\/?p=581","title":{"rendered":"The black hole at the center of our galaxy"},"content":{"rendered":"<p><a href=\"http:\/\/arxivblog.com\/wp-content\/uploads\/2008\/08\/supermassive-black-hole.jpg\" title=\"supermassive-black-hole.jpg\"><img decoding=\"async\" src=\"http:\/\/arxivblog.com\/wp-content\/uploads\/2008\/08\/supermassive-black-hole.thumbnail.jpg\" alt=\"supermassive-black-hole.jpg\" \/><\/a><\/p>\n<p>Is there a supermassive black hole at the center our galaxy, asks Mark Reid from the Harvard Smithsonian Center for Astrophysics in Cambridge.<\/p>\n<p>There sure is and Reid gives a good account of the evidence to prove it.<\/p>\n<p>How can astronomers be so sure?\u00a0 The first evidence began to emerge in the 1950s when the first radio telescopes spotted a mysterious source of radio waves from the center of the Milky Way in the constellation of Sagittarius. This source was given the name Sagittarius A.<\/p>\n<p>Better observations in the 1970s led to estimations that this source was small, less than the size of our solar system.<\/p>\n<p>Towards the end of the 70s other evidence emerged. The movement of gas clouds near Sagittarius A indicated they it must circling a a compact mass several million times greater than the Sun. Then various stars were observed circling this mass, the most recent being a star called S2 which orbits Sagittarius A every 15.8 years. This implies that Sagittarius A is a point mass some 6 million times the sun&#8217;s mass<\/p>\n<p>Then astronomers proved that the radio source and the gravitational\u00a0 mass were centred at the same point. Other evidence of a weak infrared source at the same point also turned up.<\/p>\n<p>And the clincher was that Sagittarius A is motionless relative to the rest of the Milky Way. In other words, the entire galaxy revolves around this object.<\/p>\n<p>That kind of evidence is overwhelming. It&#8217;s hard to think of anything with such a dim optical signature that could create such a high mass density (although there are some possibilities, the most obvious being a cluster of dark stars).<\/p>\n<p>Nevertheless, most astronomers are convinced we&#8217;ve got a super massive black hole on our doorstep and it&#8217;ll take some spectacular contradictory evidence to change their minds.<\/p>\n<p>Ref: \u00a0 <a href=\"http:\/\/arxiv.org\/abs\/0808.2624\">arxiv.org\/abs\/0808.2624<\/a>: Is There a Supermassive Black Hole at the Center our Galaxy<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Is there a supermassive black hole at the center our galaxy, asks Mark Reid from the Harvard Smithsonian Center for Astrophysics in Cambridge. There sure is and Reid gives a good account of the evidence to prove it. How can astronomers be so sure?\u00a0 The first evidence began to emerge in the 1950s when the [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,7],"tags":[],"class_list":["post-581","post","type-post","status-publish","format-standard","hentry","category-hellraisin","category-stars-in-their-eyes"],"_links":{"self":[{"href":"http:\/\/arxivblog.com\/index.php?rest_route=\/wp\/v2\/posts\/581","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/arxivblog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/arxivblog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/arxivblog.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/arxivblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=581"}],"version-history":[{"count":0,"href":"http:\/\/arxivblog.com\/index.php?rest_route=\/wp\/v2\/posts\/581\/revisions"}],"wp:attachment":[{"href":"http:\/\/arxivblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=581"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/arxivblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=581"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/arxivblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=581"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}