A confused fish swims low across the south on autumn nights. It's the faint constellation Piscis Austrinus, the southern fish. Tonight, it clears the southeastern horizon by nightfall, and stands due south by around 10 or 11 o'clock. It's easy to pick out because its brightest star, Fomalhaut, is the only prominent star in that region of the sky.
Fomalhaut represents the mouth of the fish, so you might expect it to lead the constellation across the sky. But it doesn't. Instead, as Earth turns on its axis, Piscis Austrinus appears to swim tail-first.
Ancient mythology doesn't give much of a clue as to why the fish swims backwards. In one story, the constellation represented the god who brought civilization to the people of Babylonia. And in ancient Persia, Fomalhaut was considered one of four royal "guardians of heaven."
The constellation is part of a large area of the sky that's known as "the sea." It includes such watery constellations as Pisces, the fishes, and Capricornus, the sea-goat. And just above Piscis Austrinus is Aquarius, the water bearer. The boy who's represented in the figure is pouring water from an urn directly toward Fomalhaut. All of these constellations were prominent during the rainy season in the ancient Mediterranean, which is why they have a watery pedigree.
Look for the southern fish tonight, floating across the southern sky -- through the celestial sea.
Script by Damond Benningfield, Copyright 2006, 2009
For more skywatching tips, astronomy news, and much more, read StarDate magazine.