Do galaxies age 'gracefully'?
This article in Space.com,
Nature vs. Nurture in the Cosmos, there seems to be evidence of a gradual evolution of galaxies. It says:
Quote:
Scientists have long thought that young galaxies grow up into old ones, referred to as blue and red galaxies, respectively. The color indicates how actively the galaxy is churning out new stars. Younger stars shine in ultraviolet or blue light, and so galaxies bustling with star-making activity appear blue. Older stars emit infrared or red light. In aging galaxies, their "stellar reproductive" capacity has begun to shut down and so the remaining stars are just hanging out for the remainder of their lives.
About half of all galaxies are blue and half are red. It had been postulated that the two are linked, with the blue young'uns running out of star-making material and maturing into passive red galaxies.
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Now, if this analysis of galaxy star formation is correct (see pix in article for examples), where a galaxy at 7 million light years has many blue stars, while one at 33 million light years has only a peripheral remnant, and at 62 million light years nearly no blue stars, then it seems there is a natural progressions tied into time and distance for galaxy evolution.
The first ATM question is: Can a galaxy evolve to full maturity in such a short time, of only about 50 to 60 million years?
The second question is: What are we actually observing? Do we actually know this analysis of galaxy evolution based on blue stars observation is correct?
Consider this possibility: (1) that beyond a certain distance, blue stars are no longer observable, if their light shift turns towards the red; and (2) if it takes only about 60 million years for a galaxy to reach full maturity, shouldn't there be some evidence of 'star formation' beyond the 62 million light years 'horizon'? Or (3) if there are blue stars observable beyond 62+ million light years horizon, then what does it mean in terms of galaxy evolution, if these galaxies are creating new stars at any time scale? What about billions of light years away? In fact, shouldn't it all be in reverse, that older (farther away, farther back in time) galaxies show
more star formations, if the universe is expanding from a Big Bang (so called) origin?
I propose, from #3, that the above article has either not given us enough information to come to a necessary conclusion about galaxy evolution, or because older (farther away) galaxies are not showing
more star formations, that the observation is flawed. Furthermore, is about 60 million years enough time to complete a full cycle of galaxy evolution from youngster to old age, gracefully?
What we are actually seeing, in effect, is that over great distances the blue stars simply are
not observable, not even at the ultraviolet wavelength. The above hypothesis is therefore flawed because of an observational limit, that older blue stars are not observable. In fact, we should be seeing
more blue stars at billions of light years, in my opinion, if galaxies formation was more common then, closer to the Big Bang 'origin' of the universe.
What do you think?
Here's the conundrum: Looking back farther in time into the early universe, we should be seeing
more star formation, not less! ATM here?