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Fornax Cluster

January 9, 2010

Fornax, the furnace, skims the southern horizon on January evenings. It's a faint constellation that's best known not for its stars but for its galaxies.

The closest galaxy in Fornax is a satellite of our own: the Fornax dwarf, which orbits the Milky Way just as the Moon orbits Earth. This galaxy is just 440,000 light-years away.

Far beyond the Fornax dwarf is an entire galaxy cluster. In fact, it's one of the closest galaxy clusters to Earth. It's an especially photogenic cluster, thanks in large part to one prominent member.

The Fornax cluster is about 60 million light-years away. Unlike our galaxy, most of the bright galaxies in Fornax are elliptical galaxies. Such galaxies are round or oval-shaped, and they consist mostly of old stars.

But the most beautiful galaxy in the Fornax cluster is of a different type. It's a dramatic barred spiral whose brightest stars make the shape of an enormous backwards letter S. This galaxy abounds with stars young and old, as well as clouds of gas and dust that are spawning even more stars. For better or worse, this stunning galaxy bears the rather ordinary name NGC 1365.

The Fornax cluster is south of the Milky Way's disk of stars. To our north is another galaxy cluster -- the Virgo cluster -- which is almost as far from us as the Fornax cluster is. So we in the Milky Way sit midway between two big clusters of galaxies: Virgo to the north and Fornax to the south.

Script by Ken Croswell, Copyright 2009

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