Jimmy Westlake: View Southern Fish this month
October 16, 2012
Shining brightly in the southern sky as darkness falls is one of autumn's few bright stars, a blue gem named Fomalhaut (pronounced FOAM-a-low). Fomalhaut belongs to our constellation of Piscis Austrinus, the Southern Fish, which is pictured on ancient star charts as swimming belly up and swallowing the stream of water flowing from the water jug of Aquarius hovering above. In fact, the name Fomalhaut comes from the Arabic words meaning "the mouth of the fish."
In ancient Mesopotamia, Fomalhaut was considered one of the four royal stars, along with Regulus, Aldebaran and Antares. Its first appearance in the early evening signaled the arrival of fall. More recently, Fomalhaut has served as an important navigational beacon because of its far southerly position. From Northwest Colorado, Fomalhaut is the most southernly first-magnitude star visible.
Fomalhaut is 25 light years from Earth, so the light that you see tonight coming from Fomalhaut actually left the star 25 years ago, in 1987, and is arriving just now.
In 1983, NASA's IRAS satellite discovered a flattened ring of dusty debris spinning around Fomalhaut. It is theorized that the planets in our own solar system, including Earth, formed within just such a spinning cloud of dust around the newborn sun. Could Fomalhaut be in the process of building its own planetary system?
The answer to this question came in 2008 when the Hubble Space Telescope succeeded in photographing a large planet orbiting at the inner edge of Fomalhaut's dusty ring. This planet, now named Fomalhaut B, appears to be a Jupiter-sized object that orbits about 115 times Earth's distance from its star with a period of about 870 years. Planet B orbits so far from the warmth of Fomalhaut that it wouldn't seem to be a hospitable planet, at least by our standards.
Fomalhaut B was the first extrasolar planet to be captured visually in a photograph. Most extrasolar planets give themselves away by their tiny gravitational tugs on their host stars or by causing tiny eclipses as they pass in front of their stars. According to the Extrasolar Planet Encyclopedia, 841 extrasolar planets have been confirmed to date.
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To locate Fomalhaut, look due south at about 9 p.m. in mid- to late October, about a hand-span above the horizon. It's easy to locate in the southern sky because there are no other stars of comparable brightness nearby at that time.
So, next time you're outside in the cool autumn night air, glance to the south and see if you can catch the Southern Fish and its bright star Fomalhaut.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. Check out Westlake's astrophotography website at http://www.jwestlake.com.