Astronomers continue to puzzle over the recent discovery of a strange population of dense, compact galaxies that existed in the early universe but are nowhere to be seen today. They suspect the galaxies somehow puffed up into the bloated behemoths we see around us, but new research shortens the timescale during which this mysterious swelling could have happened.The problem seems to be that no one knows how they could have puffed up as quickly as they apparently have, if our galaxies are normal.
Various explanations have been proposed for why nearby galaxies are "bloated" compared to these faroff compact ones, but none accounts for all of the observations.That sounds promising, actually. Let's hope for new discoveries about our universe as a result.
Astronomers assume that the universe increased in space as well as time since the Big Bang and that nothing travels faster than light. Therefore, the light that is reaching us now from these distant galaxies started there 10 billion years ago, about 3.7 million years after the Big Bang. That means we are looking at them as they were then, not as they are now. So if we see that one of the galaxies was very compact, that means it was very compact back then. It may not even exist any mor for all we know.
This might feel weird to us, in these days of instant messaging, but ironically our ancestors might understand better than we do. Centuries ago, it took up to a year to receive a letter from India or China. So you could be hearing from a person who had actually died in the meantime (but you might not find that out until months or years later). Astronomy of the far reaches of our universe is still like that. And unless someone invents faster-than-light (FTL) travel or messaging, it always will be.
Thus, the question is, assuming that the universe is pretty much the same in all directions (yes, that's another assumption astronomers make), the question is, what happened to the compact galaxies around us, and how did it happen?
Here's the abstract.
(Note: The image is from NASA ESA Hubble, of the use of on galaxy for a gravitational telescope to see galaxies 13 billion light years away.)