beryllium732 wrote: ↑Fri May 05, 2023 10:04 am
VictorBorun wrote: ↑Fri May 05, 2023 9:56 am
beryllium732 wrote: ↑Fri May 05, 2023 8:36 am
How would it be living in that galaxy? Would the nightsky be black with lots of stars but no galaxy disc in it with an expeption of a big jet sticking out in the nightsky?
add the boredom of red-and-dead star population: almost every star is a little smaller and yellower than Sun or is a red dwarf and not seen at all
You are sure about that? Wouldn't there be a lot of Betelgeuses in the nightsky too except red dwarfs and more reddish yellow suns?
There are no (or at least extremely few) Betelgueses in the skies of any putative planet inside M87.
Betelgeuse is a young massive star. Only massive stars can become red supergiants thousands of times brighter than the Sun, and such massive stars die young. And since M87 is absolutely overwhelmingly dominated by old stars, there will be no Betelgeuses among them.
Here is how you can tell old modest red giant stars from young brilliant red supergiants. First, let's look at some young red supergiants, which are typically surrounded by many bright blue stars:
Double Cluster of Perseus Tommy Lease.png
The Double Cluster of Perseus. At least 5 and possibly 7 red supergiants stand out
among the blue stars. The clusters are believed to be some 12 million years old.
Image credit: Tommy Lease.
Old red stars keep a different company than the brilliant red supergiants with their entourage of blue stars:
Old open cluster Trumpler 5 by zirl.png
Old open cluster Trumpler 5. This cluster is similar in age to the Sun.
Red supergiants are young massive stars, and they are typically surrounded by a large number of bright blue stars. Old red stars are much more modest, much less bright, don't stand out very much, and are not surrounded by blue stars (unless there happens to be one or more blue stragglers around).
Take a look at cluster NGC 2158. This cluster may be some 14,000 light-years away, and I found a Gaia parallax for the brightest red star which suggests that the V luminosity of this star is some ~68 times solar. That is not bad, but it is so very far from the brightness of a supergiant.
As for Trumpler 5, there is a star (at lower left) that stands out. However, this is a foreground star, at "only" some 3,400 light-years, whereas Trumpler 5 proper is at a distance of some 11,000 light-years. The V luminosity of the foreground star is some ~140 solar luminosities. That is not bad, but it is still in no way comparable to a supergiant.
By comparison, HD 14270, one of the red supergiants in the Double Cluster, has a V luminosity of some 3,100 solar. AS for BM Sco, the bright red non-supergiant, its V luminosity is some 1,000 solar.
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