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Old September 8th 17, 07:46 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Posts: 273
Default A new impossible galaxy

In article , jacobnavia
writes:

Massive dead disk galaxy challenges theories of galaxy evolution

https://www.sciencedaily.com/release...0621145150.htm

This galaxy (3 times the mass of the milky way) is a compact object
spinning very fast, only 3Gy after the "bang".

Composed of old, yellow stars.

Sure, but excuse me, a star like the sun, yellow, main sequence star, is
5 Gy or more old. All stars in that galaxy (z=2.1) can't be older than
2Gy. To keep things in order, galaxy formation is questioned, but not
the big bang theory.


The idea "red or yellow old, blue young" is misleading. A blue star has
to be young, because they don't live long (main-sequence stars here;
white dwarfs are also "blue" but can be quite old). A yellow star,
however, whatever its age, was also yellow when it was young. If a
POPULATION of stars is yellow, it means a) that all the blue ones have
died or b) that no blue ones ever formed. Considering that we don't
know the IMF, much less how it comes about, one shouldn't jump to
conclusions here.

In other words, stars don't move ALONG the main sequence as they evolve,
at least not significantly.