AAO image reference AAT 91. « Previous || Next »
Top left is NE. Image width is about 15 arc min
Image and text © 1992-2010, Australian Astronomical Observatory, photograph by David Malin.
As they age, open clusters of stars begin to lose their identity. This is partly because the brighter members tend to self-destruct as supernovae, and, though the group members share a common motion through space, they are only loosely bound. Thus stars drift away from the cluster in a process that accelerates with time. However, some clusters are big enough to retain their identity much longer than usual, and Trumpler 5 is one such. Its age is estimated to be about 3 billion years, which is very old for an open cluster and it must have been a spectacular sight in its youth.
The cluster is about 11,000 light years away and seems to be at the edge of the molecular cloud in Monoceros, where star formation is producing new generations of young clusters. this location is probably the cause in significant interstellar dust absorption, which gives the cluster a slight reddish hue. The brightest star here is V493 Mon, a deep red variable carbon star that appears yellow in this image. The image is about magnitude 13 on the red and green-light plates but almost invisible (at least six magnitudes fainter) on the plate taken in blue light, absorption that is taking place in the atmosphere of the star.
UKS 29. The Cone nebula and Trumpler 5
AAT 90. The young open cluster NGC 6705, Messier 11
AAT 112. Messier 67, NGC 2682, an ancient open cluster
Constellation of Monoceros (external site)
For details of photographic exposure, search technical table by AAT reference number.
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