Quote:
Originally Posted by nutant gene 71
The time line of new blue stars in distant galaxies shows (per OP article) a time line going from more recent to older (7 MLY to 62 MLY) where blue stars progressively disappear. My term "reverse order" means that from the perspective of the light coming to us from the galaxies (light from their reference frames) should show newer blue stars formation (within the galaxies) happening in older (farther away) galaxies, and progressively disappear in newer (closer in) galaxies. Try to visualize this, because it is a relativistic phenomenon, by putting yourself in the point of view 'as if' you were looking at this from the other direction, that of the stars sending light towards us.
About your other question, "...what do you think the cosmic star formation rate should look like to us in the Milky Way, here & now, if big bang cosmology is valid?" I am not sure how to answer that, in part because I don't know if any sequence of star formation in our own galaxy has any identifiable pattern to work with. If the galaxy formed at some period of time, one would assume the stars within it evolved within a relatively short time to gather together into a galaxy around a central gravity 'black hole'. If I were observing this from a distant vantage point way beyond our galaxy, perhaps some pattern vis-a-vis other nearby galaxies (in line of sight) could show the pattern of blue star formation over time (distance), but I don't know if that answers you question. My opinion is that within a galaxy, no such progression is visible. Once an aggregate of stars forms into a galaxy, it is now its own internal phenomenon. The difference between this, one galaxy, and the star formation development from multiple galaxies (line of sight) is that the latter may show a progression with time of blue star formation. I think this is what the OP article was trying to show, but it did it in "reverse" given how the time line was presented. Can you see that? That's the main issue.
I can't do more now, must run out the door, but will study this some more and get back if find new stuff. I also have to read Coldcreation's links before going deeper.  |
The author showed a blue galaxy at 7 million light years and a red galaxy at 62 million. She just as easily could have shown a blue one that is farther away. From that, along with her loose use of young and old as if she thinks they apply to the entire galaxy, you appear to have made a great-leap inference of the evolutionary time lines of those galaxies. Beyond that, I cannot follow your line of thought. Your expressions "older (farther away) galaxies" and "newer (closer) galaxies" make no sense to me. You appear to be inferring things that the author never said and never quoted anyone else as saying.
For all we know, both galaxies may be over 10 billion years old, and for whatever reason the red one has long since exhausted its supply of gas while the blue one has not. I see nothing in the article which implies otherwise. The 55 million year difference in the lookback times is a twinkling in comparison.
From this article and others on similar topics, I would guess that the red one is the result of past mergers in which the interactions accelerated the star-forming process and in the process exhausted the supply of gas. Computer simulations indicate that such mergers also scramble the original spirals and yield a large elliptical galaxy. Given enough time, the blue components of the other one will disappear and leave it similarly red. If it does not merge with another large galaxy I would expect it to remain a disk rather than become an elliptical blob.