What are star clusters?

[Admin]

Star clusters are large gravitationally bound groups of stars that are one of the best tools astronomers have to study stellar evolution.

What are star clusters? : Read more

 

[rod]

The space.com article said, "If you have a star cluster that's 100 million years old, and then you have a star cluster that's a billion years old, you basically have two snapshots of the lives of stars," Steffen said. Comparing the two "helps you understand what's going on on the insides of the stars and how they evolved throughout their lifetimes," according to Steffen."

My experience. Dating various star clusters and globular clusters seems straightforward but does contain pitfalls too. Here is a good example from the wires today.

NGC 1605 is an old binary open cluster, study finds, https://phys.org/news/2021-10-ngc-binary-cluster.html

This report caught my attention this morning. Reference paper, NGC1605a and b: an old binary open cluster in the Galaxy, https://arxiv.org/abs/2109.14664, 29-Sep-2021. The 12 page arXiv paper link, https://arxiv.org/pdf/2109.14664.pdf.

My observation. The two open clusters are said to be separated by about 5.9 light years in space measured from the central cores. The age difference reported is 1.4 Gyr or 1.4E+9 years. If each open cluster took 230 million years to revolve around the Milky Way, in 1.4E+9 years, the open clusters complete 6 revolutions in order to explain the H-R diagram age differences found today. The arXiv paper cited shows NGC 1605 was originally considered a single, old open cluster said to be 5 Gyr old. The new observations and changes to the ages calculated show 5E+9 years old - 6E+8 years old = 4.4E+9 years age dating change for NGC 1605b. Also we have 5E+9 years old - 2E+9 years old = 3E+9 years age dating change for NGC 1605a. In a 230 million year revolution period around the galaxy, NGC 1605a completes 8.7 revolutions and NGC 1605b completes 2.6 revolutions. Initial dating of NGC 1605 showed the open cluster older than our Sun, dated via radiometric ages of meteorites to be some 4.57E+9 years old for the Sun. Quite a bit of interpretation used to redate NGC 1605 based upon the newer, and better observations.