You are here


September 17, 2012

Autumn has few stars to call its own. A few lingering stars of summer are in view during the evening, with the bright stars of winter climbing into view in the wee hours of the morning. But there’s really only one bright star that puts in its best showing during the nights of autumn: Fomalhaut, the leading light of Piscis Austrinus, the southern fish.

Fomalhaut itself is young and vigorous. It’s only a few hundred million years old, and it’s bigger and heavier than the Sun. That makes the star hotter and brighter than the Sun — one reason that Fomalhaut shines so brightly in our night sky. The other reason is that it’s a close neighbor — just 25 light-years away.

A broad disk of dust encircles the young star. The disk seems to be bounded by a giant planet that’s about 10 billion miles from Fomalhaut — more than a hundred times farther than Earth is from the Sun. Hubble Space Telescope has snapped pictures of the possible planet, although it’s so small and far away that it looks like nothing more than a tiny dot.

The supply of dust in the disk may be renewed by constant collisions between comets; more about that tomorrow.

In the meantime, look for Fomalhaut low in the southeast not long after night falls, and due south around midnight. From the northern states, it never climbs very high above the horizon, but the view is a little better from the south — a view of the only true contender for the title of “the Autumn Star.”


Script by Damond Benningfield, Copyright 2012

Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.