{"id":2199,"date":"2016-03-10T22:24:12","date_gmt":"2016-03-11T04:24:12","guid":{"rendered":"http:\/\/austinastro.org\/?p=2199"},"modified":"2016-03-10T22:24:19","modified_gmt":"2016-03-11T04:24:19","slug":"march-2016","status":"publish","type":"post","link":"https:\/\/austinastro.org\/index.php\/2016\/03\/10\/march-2016\/","title":{"rendered":"March 2016"},"content":{"rendered":"
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by Brian Cuthbertson<\/h4>\n<\/div>\n<\/div>\n
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History tells us that March comes in like a lion and goes out like a lamb. Maybe that was before global warming: March has already come in like a lamb, with plenty of mild and clear nights, at least here in central Texas. And while that may not last forever, it’s a perfect opportunity to get out and poke around in the spring skies. As usual, a few morsels are below. But whatever you like to chew on, do get out and enjoy!<\/p>\n

21 LMi rating EASY<\/strong>
\n \u00a0\u00a0 star in Leo Minor<\/strong>
\n \u00a0\u00a0 RA 10h 07.4m\u00a0 Dec +35d 14.7′\u00a0 (2000)<\/strong>
\n \u00a0\u00a0 Magnitude 4.5<\/strong><\/p>\n

Which star cluster is so close that you can’t see it in binoculars? How about Collinder 265, also known as the Ursa Major Moving Cluster? Centered about 75 light-years away, the UMa Moving Cluster is closer than any other known star cluster.<\/p>\n

21 LMi is an outlying member of this cluster, which was was first identified in 1869 by Richard Proctor. He determined that the 5 bright central stars of the Big Dipper (in Ursa Major) were moving in the same direction through space at the same speed, a conclusion confirmed 3 years
\nlater by William Huggins.<\/p>\n

The elongated core of the cluster, at least 10×20 light-years in size, translates into an apparent diameter greater than 20 degrees across the sky. As a result, although the UMa Moving cluster is centered on the Big Dipper, it also includes stars from Corona Borealis to Leo and Leo Minor, including 21 LMi.<\/p>\n

R UMa\u00a0 rating MEDIUM<\/strong>
\n \u00a0\u00a0 variable star in Ursa Major<\/strong>
\n \u00a0\u00a0 RA 10h 44.7m\u00a0 Dec +68d 46.3′\u00a0 (2000)<\/strong>
\n \u00a0\u00a0 Magnitude 7-13<\/strong><\/p>\n

R UMa is a pulsating red giant star of the Mira class, closely comparable to Mira in period, range and spectral type. Located in northern Ursa Major about 4 degrees east of galaxy M81, it was the first long-period variable star found in Ursa Major, by Pogson in 1853.<\/p>\n

Although it occasionally reaches 6.7 or so at high maximum, R has a usual range of 7.5 to about 13 in a cycle averaging 302 days. When near the bottom of its cycle, R is one of the reddest of the long-period variables; however, the intense color weakens as the star rises to maximum. And as it brightens it does so about twice as fast as it fades, with a min to max time of about 116 days. If you’re interested in following this curve, note that the last maximum of R was 12 November 2015.<\/p>\n

R has a peak luminosity of about 250 times that of the Sun. However, it is about 6 times more remote than Mira, with an estimated distance of around 1350 light-years. And it’s also receding from us at about 20 miles per second, so don’t wait too long to take a look!<\/p>\n

Leo I\u00a0\u00a0 rating HARD<\/strong>
\n \u00a0 Local Group dwarf galaxy, near Regulus<\/strong>
\n \u00a0 RA 10h 8.4m\u00a0 Dec +12d 18.0′\u00a0 (2000)<\/strong>
\n \u00a0 Magnitude 9.8,\u00a0 diameter 10′ (1000 LY),\u00a0 distance 250 kpc (800000 LY)<\/strong><\/p>\n

Leo I is a dwarf spheroidal (Hubble type E3) member of our Local Group of galaxies. Lying over half a million light-years away, it’s one of the most distant of 11 Local Group dwarf galaxies. Most of the smaller Local Group members resemble this object. Star formation in Leo I ended about 10 billion years ago, compared to more than 15 billion years ago for a typical globular cluster like M13.<\/p>\n

Visually, Leo I is a swarm of stars magnitude 20 and fainter. Although it has a total magnitude near 10th, its low surface brightness (due to its 10′ disk) and its proximity to Regulus (which is 15″ south) make it a difficult object. It can be observed with a 17-inch telescope if Regulus is kept out of the field.<\/p>\n

If you don’t have a 17-inch scope handy, a nice APOD image by David Malin
\ncan be found at:\u00a0\u00a0http:\/\/antwrp.gsfc.nasa.gov\/apod\/ap991003.html<\/a><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

by Brian Cuthbertson History tells us that March comes in like a lion and goes out like a lamb. Maybe that was before global warming: March has already come in like a lamb, with plenty of mild and clear nights, at least here in central Texas. And while that may not last forever, it’s a […]<\/p>\n","protected":false},"author":573,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[47],"tags":[],"class_list":["post-2199","post","type-post","status-publish","format-standard","hentry","category-aas_ot"],"_links":{"self":[{"href":"https:\/\/austinastro.org\/index.php\/wp-json\/wp\/v2\/posts\/2199","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/austinastro.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/austinastro.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/austinastro.org\/index.php\/wp-json\/wp\/v2\/users\/573"}],"replies":[{"embeddable":true,"href":"https:\/\/austinastro.org\/index.php\/wp-json\/wp\/v2\/comments?post=2199"}],"version-history":[{"count":0,"href":"https:\/\/austinastro.org\/index.php\/wp-json\/wp\/v2\/posts\/2199\/revisions"}],"wp:attachment":[{"href":"https:\/\/austinastro.org\/index.php\/wp-json\/wp\/v2\/media?parent=2199"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/austinastro.org\/index.php\/wp-json\/wp\/v2\/categories?post=2199"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/austinastro.org\/index.php\/wp-json\/wp\/v2\/tags?post=2199"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}