AAO image reference AAT 113. « Previous || Next »
Top left is NE. Image width is about 16 arc min
Image and text © 1992-2010, Australian Astronomical Observatory, photograph by David Malin.
In March, 1871 Charles Messier noted as number 93 in his famous catalogue this conspicuous group as a cluster of small stars. It was one of the last objects that Messier himself listed though he lived until 1817. The cluster is in the southern constellation of Puppis (known to Messier as Argo Puppis) and is in a rich part of the Milky Way, almost on the Galactic equator. The group is quite compact and is on the threshold of naked-eye visibility under good conditions. It is at a distance of over 3000 light years.
About 80 stars have been identified as being members of the cluster, however, as in most open clusters, a mere handful contribute most of the light, reflecting the broad distribution of stellar luminosities (and thus stellar masses) found in objects of this kind. M93 is at the upper end of the youth scale however, since its stars are estimated to be over 100 million years old.
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