NGC 6397

NGC 6397 is a large and loosely scattered globular cluster well seen in binoculars with an apparent magnitude of 6.7.

The cluster is the second closest to Earth at 7200 light years away (the closest is M4 in Scorpius). NGC 6397 contains nearly half a million stars.

Studies in 2004 of two central stars in this cluster concluded with putting the age of the Milky Way at 13.6 billion years old, not much younger than the Universe itself.

The cluster is to the southeast of alpha, in the same field: binoculars.

If you now place the cluster (and the nearby star pi Arae) at the upper edge of your glasses, beta Arae comes into view: binoculars. Beta Arae is an orange supergiant 600 light years away. With a magnitude of 2.8, it now appears to be slightly less bright than alpha.

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1999-2014 by Richard Dibon-Smith.