Steamboat Pilot & Today

Jimmy Westlake

Jimmy Westlake's Celestial News column appears Tuesdays in the Steamboat Today.

Find more columns by Westlake here.

Shining brightly in the southern sky as darkness falls is one of autumn’s few bright stars, a blue gem named Fomalhaut. Fomalhaut belongs to the constellation Piscis Austrinus, the Southern Fish, pictured on ancient star atlases 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.”

Fomalhaut was considered one of the four royal stars in ancient Mesopotamia, 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. In fact, from Northwest Colorado, Fomalhaut is the most southerly first-magnitude star visible.

The light that you see coming from Fomalhaut tonight actually left the star 25 years ago, in 1986, and is just now arriving. In 1983, NASA’s IRAS satellite discovered a flattened ring of dusty debris spinning around this star. 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-class object that orbits about 115 AU from its star with a period of 872 years. One AU (astronomical unit) is equal to the Earth’s average distance from the sun — about 93 million miles — so Fomalhaut b orbits very far from the warmth of Fomalhaut and would not seem to be a hospitable planet. 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 them.

To locate Fomalhaut, look due south at about 7 p.m. late this month and 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. So next time you’re outside in the early evening, glance to the south and see if you can spot it.

Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. Check out “Jimmy’s 2012 Cosmic Calendar” of sky events at www.jwestlake.com. It features 12 of his best astrophotographs and a day-by day listing of cool celestial events that you and your family can have fun watching in the coming year. Proceeds from the sale of Cosmic Calendars support the CMC SKY Club.