Galaxy clusters are large clouds of hot gas, seemingly-ideal places to observe gas cooling and condensing into stars. Yet, we don't see that happening. Here's a look at how black holes and turbulence are conspiring to keep galaxy clusters underpopulated with hot new stars.
Hubble telescope has just produced this brain-expanding image of Galaxy Cluster Abell 1689, a dense thicket of galaxies and globular clusters 2.25 billion light years away. It's also a region of the universe that's rich in dark matter.
This is the Hercules galaxy cluster, located relatively close to us at just 500 million light-years away. But the way its galaxies are colliding with each other makes it look like a throwback to the chaos of the early universe.
This part of space may look like nothing special, but it's actually home to a tightly packed "galaxy city," composed of thirty extremely ancient galaxies. It's a big find... and it took thousands of hours of observation before anyone noticed.
Abell 520 is one of the most gigantic mergers of galaxies we've ever seen, and it's definitely the most baffling. As galaxies smashed together and parted away, they seemingly left their dark matter behind. That's supposed to be completely impossible.
Every cosmic phenomenon deserves its own unique claim to fame, but Abell 2052 deserves better than this. Its gas jerks back and forth like a drink sloshing around in a glass. It's like the cosmic equivalent of a tipsy uncle.
This galaxy cluster is nicknamed El Gordo, which means "The Fat One" in Spanish. Located seven billion light-years away, it's the biggest cluster ever found at that distance — and it's resounding proof that dark matter is everywhere in the cosmos.
Dark energy accounts for 70% of everything in the universe, and yet we know almost nothing about it. Now a new model meant to explain some impossibly massive galaxy clusters is here, to make dark energy even more fiendishly complex.
At first glance, this looks like just another star field. But almost every source of light in this image is actually one of the 190 galaxies making up the massive Perseus Cluster, one of the nearest such clusters to Earth.
If you're going to name a cluster of galaxies after the mythological character who unleashed evil on the world, this particular is a pretty good choice. It's a cacophonous, mixed-up mishmash of four older clusters, plus plenty of dark matter.
Gravity forces galaxies that are relatively close together to form clusters, which in turn form superclusters between vast stretches of cosmic void. But now there's an even bigger level of organization...and we have no idea how to explain it.