AAO image reference AAT 114. « Previous || Next »
Top left is NE. Image width is about 10 arc min
Image and text © 1992-2010, Australian Astronomical Observatory, photograph by David Malin.
This otherwise undistinguished cluster is one of many in the sparkling ornaments of the southern constellation of Scorpius. It is marked by a bright yellow star (spectral type K5) which happens to be in the foreground at a distance of about 1000 light years. The cluster itself is about 3,500 light years from the Sun.
The cluster is slightly dimmed by foreground dust. This so-called interstellar extinction is common with object close to the Galactic plane. Despite this, it is possible to estimate the age of the cluster by measuring the color and relative brightness of its stars. The age turns out to be about 50 million years, which is quite mature for an open cluster of this type. By now, most of the brightest stars will have turned into supernovae and vanished, leaving this quite modest group to compete with the many bright clusters of stars in this direction. The cluster was first noted by one of the earliest modern explorers of the southern sky, Abbe Lacaille, on his journey to South Africa in 1751-52.
AAT 91. The old open cluster Trumpler 5
Constellation of Scorpius (external site)
For details of position and photographic exposure, search technical table by AAT reference number.
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