Jimmy Westlake: Catch Fomalhaut and the Southern Fish
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 upside down 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 the season of fall.
More recently, Fomalhaut has served as an important navigational beacon because of its far southerly position. Fomalhaut is the most southerly first magnitude star visible from northwestern Colorado.
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 1991.
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 about three times the mass of our biggest planet, Jupiter, and orbits 115 astronomical units from its star with a period of 870 years.
One astronomical unit is equal to the average distance between the Earth and sun, about 93 million miles. Planet b orbits so far from the warmth of Fomalhaut that it wouldn’t seem to be a hospitable planet, 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 (http://exoplanet.eu/catalog.php), 3,533 extrasolar planets have been confirmed as of Oct. 2.
To locate Fomalhaut, look due south around 10 p.m. in early to mid-October, about a hand-span above the horizon. It’s pretty easy to locate in the southern sky because there are no other bright stars in the area.
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 singularly bright star Fomalhaut.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Steamboat Springs Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper. Check out Jimmy’s astrophotography website at http://www.jwestlake.com.
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