bystander wrote: ↑Mon Jul 27, 2020 4:17 pm
Stellar Sweet Shop
ESA Hubble Picture of the Week | 2020 Jul 27
Looking its best ever is the star cluster NGC 2203
, here imaged by the NASA/ESA Hubble Space Telescope. Aside from its dazzling good looks, this cluster of stars
contains lots of astronomical treats that have helped astronomers puzzle together the lifetimes of stars.
A main sequence
star, like our Sun, is the term applied to a star during the longest period of its life, when it burns fuel steadily. Our Sun’s fuel will run out in approximately 6 billion years, and it will then move on to the next stage of its life when it will turn into a red giant
. Astronomers studying NGC 2203, which contains stars that are roughly twice as massive as our Sun, found that their rotation might be a factor as to why some of the stars stay longer than usual in this main-sequence phase of their life.
This is the best resolution obtained of the star cluster
Wow, that's an amazing cluster!
It has been called both an open cluster
and a globular cluster.
It looks for all the world like a globular cluster to me. Is it possible for an open cluster to contain so
many stars? Or is NGC 2203 so metal-rich that astronomers hesitate to use the same designation for it that is used for old metal-poor vast congregations of stars?
How old is NGC 2203? Sci News
calls it "an intermediate-age open cluster". What's an intermediate-age open cluster?
NGC 188 is one of the oldest open clusters of the Milky Way. According to Wikipedia
, it is 6.8 billion years old. This is very old for an open cluster. So how old is an intermediate-age open cluster? 3 billion years? 2 billion years?
Okay, answer: According to arXiv paper Nearly coeval intermediate-age Milky Way star clusters at very different dynamics evolutionary stages
by Andrés E. Piatti, Mateus S. Angelo and Wilton S. Dias, an intermediate-age cluster is 0.8 - 4 billion years old
On the other hand, 6.8 billion years is pretty young for a "true" globular cluster. I don't think the Milky Way has any globulars this young.
NGC 2203 is an outlier of the Large Magellanic Cloud. I'm not surprised. A cluster as magnificent as this one would have been well known already if it had been a Milky Way cluster.