What happens when a pair of the most mysterious and powerful objects in the universe collide? Astronomers are watching two such collisions in progress with the help of NASA hardware.
Scientists used NASA’s Chandra X-ray Observatory to track two pairs of black holes in dwarf galaxies in the midst of violent encounters. They published details of the colliding pairs this week in The Astrophysical Journal.
One of the pairs appears to be in the late stages of an impact, a process called a merger that will eventually become a giant black hole and a larger galaxy. It is in a cluster of galaxies called Abell 133 about 760 million light-years from Earth. The researchers named the fused pair “Mirabilis” after an endangered species of hummingbird.
The other pair is in the cluster Abell 1758S about 3.2 billion light-years away. It appears to be in the early stages of a merger, with a “bridge” of stars and other material connecting the two galaxies acting as the primary tip of the cosmic collision.
This isn’t the first time astronomers have found black holes playing cosmic chicken, but it’s the first of the behemoths at the center of dwarf galaxies.
“Astronomers have found many examples of black holes on collision courses in massive galaxies that are relatively close,” said Marko Micic, a graduate student at the University of Alabama in Tuscaloosa who led the study, in a statement. “But the search for them in dwarf galaxies is extremely challenging and has so far failed.”
What is a black hole? The dark, mysterious beasts of the universe
See all photos
This says less about the rarity of colliding dwarf galaxies than it does about how much more difficult it is to study the fainter dwarf galaxies – the discovery is a product of improving technology and techniques. In this case, researchers used Chandra’s superpowers to search for superheated material surrounding black holes that emit a lot of X-rays. They looked for pairs of black holes in colliding dwarf galaxies and found two sets.
Dwarf galaxies are of interest to astrophysicists and cosmologists because they are like a window back into deep cosmic time and may provide insights into our own galactic youth.
“Most of the dwarf galaxies and black holes in the early universe are likely to be larger now, thanks to repeated mergers,” said co-author Brenna Wells, also of the University of Alabama at Tuscaloosa. . “In some ways, dwarf galaxies are our galactic ancestors, evolving over billions of years to create massive galaxies like our own Milky Way.”
Fortunately, our own galaxy isn’t set to collide with another any time soon. But if you happen to be around 4 billion years, prime for the Andromeda effect.