Most
of the time, we think that things around us that are older are naturally more
mature (or worn out, depending on the object). Interestingly, globular clusters
may not follow this natural course of thought. Globular clusters are amongst
one of the oldest objects in the universe, with ages ranging from 9 to 13
billion years old. This is because they are one of the first stars to form
since the universe was born. Most astronomers think that understanding the
evolution of globular clusters could give us important insight on the evolution
of galaxies around us.
Studies
of globular clusters NGC6397 and NGC6121 show that there are some globular
clusters are more immature than previously thought. There are three “age”
stages (this is not age in years, but rather indicates where the globular
cluster is in its evolution) that globular clusters go through: adolescence,
middle age, and old age. Comparing NGC6397 and NGC6121, NGC6397 has a lower
encounter rate than NGC6121, which should be reflected by having fewer X-ray
sources (if we assume that they are both middle age). However, NGC6397 has
abundant X-Ray sources, which indicates that it is more mature than NGC6121.
Studies have discovered that only three out of the thirteen globular clusters
have abundant X-Ray sources like NGC6397, meaning that ten globular clusters
are actually still adolescents.
This
leads me to ask how this new line of discovery affects our understanding of
galaxies, since we believe that the evolution of globular clusters helps us to
understand the evolution of galaxies. How can we apply what we know now to the
Milky Way? Does this say something about the age of our galaxy as well, and how
it is currently behaving? Since globular clusters are one of the oldest things
in the universe but they are still immature, would they actually have
explanatory power for our own galaxy?
Sources:
http://chandra.harvard.edu/press/08_releases/press_042808.html
http://www.unexplained-mysteries.com/forum/index.php?showtopic=126051
http://www.cosmosmagazine.com/news/oldest-objects-space-are-mere-juveniles/
Interesting questions about what aging says about the evolution of galaxies. The lack of aging in older star clusters based on the level of Xrays seems kind of contradictory. It seems that this would provide an issue with learning about the evolution of the universe through these stars since, although they are old, the older ones do not appear to be aging.
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