Figure 1: The Hercules Globular Cluster (M13) imaged at Lac Teeples on May 22, 2023.
I have a fondness for Globular Clusters because they are such odd things. They are known to have very unique populations of old stars. The stars in these objects are so old that they have few atoms other than Hydrogen or Helium. We call this “low metallicity”, following the astronomer’s logic that anything heavier than Helium must be a metal. The “metals” were formed after the big bang within stars and have been spread out across the universe over time as stars have exploded. In the beginning there was practically nothing but Hydrogen and a bit of Helium.
The Hercules cluster in Figure 1 is so-called because it is a bright object in the Hercules constellation. It is also known as Messier-13, M13, #13 on Mr. Messier’s list of objects that look like comets but are not, in fact, comets.
There is nothing special about this image and I would not have posted it but for a recent news story. A different Globular Cluster, Messier 92, or M92, also part of the Milky Way and incidentally also in the Hercules constellation, was found to be so old that it pre-dates the Milky Way. Yes, this ball of stars was around before the Milky Way, perhaps forming out of the same gas that later created our galaxy, or perhaps arriving as an immigrant from some foreign place.
The recent age estimate for M92 is 13.8 billion years. The current estimated age of the universe is 13.8 billion years. Astronomer Martin Ying of Dartmouth College noted that “It helps us set the lower bound of the age of the universe. We don’t expect M92 to be born before the universe, right?” (see article linked below). Well, do we? The universe is under no obligation to make sense to us.
I have a good image of M92 from a few years ago, shown in Figure 2. A good image of another Globular Cluster, M3, shown in Figure 3.
Figure 2: Messier 92 Globular Cluster: Older than the hills. Imaged at Lac Teeples on August 16, 2021.
Figure 3: Messier 3 Globular Cluster. Imaged at Lac Teeples on May 13, 2020.
I’ve written in previous posts that I think of these clusters as mini Galaxies all to themselves. The stars are bound to the cluster by gravity and cannot escape. Their stellar population is different from the more diverse Milky Way.
Just in the past few years we have learned a great deal about the Milky Way because of some fantastic efforts to catalog stars. Humans have been creating catalogs of stars for several thousand years and it seems that the effort remains worthwhile. Of course we are now cataloging them using computerized scans of the sky with telescopes vastly more powerful than the eyes of the ancients. The results are similar – we are leaning about the structure of our universe.
This Hercules M13 image was captured at Lac Teeples on May 22, 2023. The telescope was the RASA-11 and the camera was the ZWO ASI-6200MC colour camera. A total of two hours of one-minute subframes were used to create this image.
The image of M92 was captured at Lac Teeples on August 16, 2021. The telescope was the RASA-11 and the camera was the ZWO ASI-6200MC colour camera.
The image of M3 was captured at Lac Teeples on May 13, 2020 using the Celestron 11” Schmidt—Cassegrain telescope and the ZWO ASI-294MC colour camera.
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