This is the kind of text that interests me, but I find it hard to understand it. Alternatively, the person who wrote the text is very good at making science but not very good at explaining it in words.
Indeed. We still believe that the main sequence is the place where stars typically hang out. Since the majority of stars in the universe are tiny red dwarfs, which burn their fuel so slowly that they are expected to stay on the main sequence for perhaps trillions of years, while at the same time the star-making ability of the universe itself is winding down, most stars are indeed expected not only to lie but to stay on the main sequence for trillions of years.
where the larger a galaxy’s mass, the higher its efficiency to form new stars.
Really? In the nearby universe, starbursts are more common in low-mass galaxies than in high-mass ones. Many of the largest galaxies in the nearby universe are massive ellipticals inside galaxy clusters, and they form very few stars at all. It was probably the other way in the distant past, because a "red and dead" giant galaxy like M87 must have been very active at star formation at some time during its youth.
However, every now and then a galaxy will display a burst of newly-formed stars that shine brighter than the rest. A collision between two large galaxies is usually the cause of such starburst phases
Yes, in the past. In the nearby universe some small galaxies display starbursts even though they don't seem to be colliding with anything at all, except perhaps a molecular cloud.
The question astronomers have been asking is whether such starbursts in the early universe were the result of having an overabundant gas supply, or whether galaxies converted gas more efficiently.
It doesn't have to be an either/or kind of question. It seems obvious that the gas supply must have been greater in the early universe than it is today. There was a time when most stars that exist today hadn't formed at all, and the "free gas" that went into making them must have been available for starmaking to those galaxies that made them, and most stars in the universe were made in the distant past. So, there was a lot of gas around. And while some of the gas that was converted into stars has been returned to the universe through supernovas and planetary nebulas, most gas that ended up inside stars has been locked up inside small red dwarf stars that will hang on to their gas for trillions of years. Also the universe was much smaller in the past, so the gas that was there must have been more concentrated.
Of course it
is a very interesting observation that the galaxies in the distant past were more efficient at turning gas into stars than most galaxies are in the nearby universe.
This was feasible by the advent of Atacama Large Millimeter Array (ALMA), located on a mountaintop plateau in Chile, which works in tandem to detect electromagnetic waves at a wavelength range in the millimeter (pivotal for studying molecular gas) and a sensitivity level that is just starting to be explored by astronomers today.
It works in tandem with what?
The researchers found the amount of CO-emitting gas was already diminished even though the galaxy continued to form stars at high rates.
The CO-emitting gas was already diminished compared with what?
These observations are similar to those recorded for starburst galaxies near Earth today, but the amount of gas depletion was not quite as rapid as expected.
How was the gas depletion measured and what was the expected rate of depletion?
This led researchers to conclude there might be a continuous increase in the efficiency depending on how high above the rate of forming stars is from the main sequence.
Huh?
Ann
Edit: The text may originally have been written in Chinese. Could this be a case of running a text through Google translate and hoping for the best? I once tried to translate a text about Eta Carina from German into English using Google translate. The Google-translated text told me that Eta Carina is an asterisk sitting in a fog.
But it seems to me that in this case, there are more things missing than have been lost in translation.
