Hubble telescope helps find six 'dead' galaxies from the early universe:
You'd think large galaxies in the early universe would have had plenty of 'fuel' left for new stars, but a recent discovery suggests that wasn't always the case. Astronomers using the Hubble Space Telescope and the Atacama Large Millimeter/Submillimeter Array (ALMA) have found six early galaxies (about 3 billion years after the Big Bang) that were unusually "dead" — that is, they'd run out of the cold hydrogen necessary for star formation. This was the peak period for star births, according to lead researcher Kate Whitaker, so the disappearance of that hydrogen is a mystery.
The team found the galaxies thanks to strong gravitational lensing, using galaxy clusters to bend and magnify light from the early universe. Hubble identified where stars had formed in the past, while ALMA detected cold dust (a stand-in for the hydrogen) to show where stars would have formed if the necessary ingredients had been present.
The galaxies are believed to have expanded since, but not through star creation. Rather, they grew through mergers with other small galaxies and gas. Any formation after that would have been limited at most.
From CNET we read:
"The most massive galaxies in our universe formed incredibly early, just after the Big Bang happened," Kate Whitaker, a professor of astronomy at University of Massachusetts-Amherst and lead author of a new study, said in a statement. "But for some reason, they have shut down. They're no longer forming new stars."
It turns out, some old galaxies merely ran low on star fuel, or cold gas, early on in their lifetimes. The results of the group's study were published Wednesday in the journal Nature and could rewrite our knowledge of how the universe evolved.
Journal Reference:
Katherine E. Whitaker, Christina C. Williams, Lamiya Mowla, et al. Quenching of star formation from a lack of inflowing gas to galaxies, Nature (DOI: 10.1038/s41586-021-03806-7)
(Score: 2) by Runaway1956 on Tuesday September 28 2021, @05:47PM (1 child)
Dark matter? Wiggle room? Dark matter is wiggle room, in and of itself. Dark matter tries to explain matter that we are unable to observe, right? Roughly 80% of the matter in the universe is unobservable, according to one estimate. But, is dark matter necessary to explain that? I don't think so. TFA explains that we have previously failed to observe entire galaxies that are observable, once we learn the trick to finding them.
Then, we have other new discoveries, such as https://news.ucsc.edu/2020/05/missing-matter.html [ucsc.edu]
Maybe there really is "dark matter", with some strange attributes that we don't understand. On the other hand, maybe not. Maybe all that missing matter is simply too far away to detect with today's instruments. Or maybe a lot of it is simply obscured by closer matter. Or, maybe the aliens stole it, and stored it inside of a Dyson sphere. Or, instead of aliens, there are more black holes than we have accounted for that are hiding all that matter.
(Score: 2) by maxwell demon on Wednesday September 29 2021, @06:35AM
Wrong. Dark matter is, by definition, matter that we are unable to observe.
The favoured candidate for dark matter is WIMPS (weakly interacting massive particles), but that is by far not the only hypothesis. There's also the MACHOS (massive compact halo objects) hypothesis, that says the missing matter is, well, massive compact halo objects (such as the black holes you mentioned). So black holes would not be an alternative to dark matter, it would be one possible form of dark matter.
The option of the matter being too far away for us to see is, however, not possible. Matter in galaxies close enough to be seen quite obviously is not too far away to be seen (or else we wouldn't see those galaxies to begin with).
The Tao of math: The numbers you can count are not the real numbers.