Home > Stars & Star Clusters > Berkeley 17 – The Oldest Open Cluster in the Milky Way

Berkeley 17 – The Oldest Open Cluster in the Milky Way

The Berkeley Open Cluster catalogue contains 104 clusters observed by astronomers at the University of California, Berkeley using the Palomar Observatory Sky Survey (POSS) plates. The catalogue was published in 1958 by Jiri Alter et al.  The Berkeley clusters are a fascinating and challenging group to explore and contain some of the oldest and most distant open clusters in our galaxy. Over the next few months i’m going to introduce you to a few of these clusters with the help of some images taken using the GRAS remote telescopes in New Mexico.

Berkeley 17 (Be17) is found in the constellation Auriga and currently holds the title for the oldest open cluster in our galaxy. There is some dispute over the maximum age estimate depending on which astronomical paper you read,  but the average figure is somewhere around 10.06 – 10.08 billion years old (a 2006 paper gives a date range of 8.5- 9 billion years, but does not rule out a greater age) . Be17 does have a rival for oldest open cluster, NGC 6791 in Lyra, but until a definitive date range is provided for the latter Be17 reigns supreme.

Like most of the Berkeley clusters Be17 is very faint with magnitudes of its estimated 400 member stars in the range 17.8 – 20.0. It appears as a slightly more dense clump in the centre of the photo below and is largely populated by old red stars of relatively high metallicity with no evidence of any blue stragglers which are more common in older globular clusters. Be17 is thought to inhabit the thin disk of our galaxy and therefore helps to date the formation of the thin disk as well as supplying an upper date limit for the formation of the thick disk and halo.

Imaged using GRAS 03  TAK TOA 150/FLI ML8300 one shot colour camera. 24th September 2011 09:11:37 UTC   RA: 05h 20m 32.0s DEC: 30° 34′ 30″ (J2000)  20 minutes exposure @ 2 x 600 seconds.

Categories: Stars & Star Clusters
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