Hubble Captures a Black Hole That is Forming Stars, Not Absorbing Them

The Hubble Space Telescope has observed a black hole at the center of a dwarf galaxy that is not acting like the destructive monsters they are often portrayed as. Instead, this black hole is creating stars rather than absorbing them.

The black hole is at the center of dwarf galaxy Henize 2-10 that lies 30 million light-years away in the southern constellation Pyxis. According to NASA, the black hole is apparently contributing to a “firestorm” of new star formation taking place in the galaxy.

A Galaxy 1/10 The Size of the Milky Way

Ten years ago, Henize 2-10 was the center of debate as to whether dwarf galaxies were home to black holes proportional to supermassive ones found at the center of large galaxies. Now, as a black hole has been spotted at its core and it is not acting as expected, Henize 2-10 (which has just one-tenth the number of stars in the Milky Way) may pay a large role in the discovery of where supermassive black holes originate.

Amy Reines published the first evidence that there was a black hole in the Henize 2-10 galaxy back in 2011 and is the principal investigator of these new observations of it that have been published in the January 19 issue of Nature.

“From the beginning, I knew something unusual and special was happening in Henize 2-10, and now Hubble has provided a very clear picture of the connection between the black hole and a neighboring star-forming region located 230 light-years from the black hole,” Reines says.

Dwarf Galaxy Henize 2-10
Henize 2-10 | Image Credit: NASA, ESA, Zachary Schutte (XGI), Amy Reines (XGI); Image Processing: Alyssa Pagan (STScI)

Opposite of the Expected Behavior

The way the stars are being created is unusual and different than what is observed in larger galaxies. Gas can be seen swirling around the black hole at the center of Henize 2-10 black hole and then slamming into a dense “cocoon” of gas within the galaxy.

“Hubble spectroscopy shows the outflow was moving about one million miles per hour, slamming into the dense gas like a garden hose hitting a pile of dirt and spreading out. Newborn star clusters dot the path of the outflow’s spread, their ages also calculated by Hubble,” NASA explains.

This is the opposite of what is seen in larger galaxies, where materials that fall towards the black hole are moved away by surrounding magnetic fields that form blazing jets of plasma that move close to the speed of light. Gas clouds that are caught in that path would be heated beyond their ability to cool back down and form stars. But the gentler outflow of gas from the black hole in Henize 2-10 is compressed just enough to facilitate star formation.

Pullout of the central region of Henize 2-10
A pullout of the central region of dwarf starburst galaxy Henize 2-10 traces an outflow, or bridge of hot gas 230 light-years long, connecting the galaxy’s massive black hole and a star-forming region. Hubble data on the velocity of the outflow from the black hole, as well as the age of the young stars, indicates a causal relationship between the two. A few million years ago, the outflow of hot gas slammed into the dense cloud of a stellar nursery and spread out, like water from a hose impacting a mound of dirt. Now clusters of young stars are aligned perpendicular to the outflow, revealing the path of its spread. | Credits: NASA, ESA, Zachary Schutte (XGI), Amy Reines (XGI); Image Processing: Alyssa Pagan (STScI)

“At only 30 million light-years away, Henize 2-10 is close enough that Hubble was able to capture both images and spectroscopic evidence of a black hole outflow very clearly. The additional surprise was that, rather than suppressing star formation, the outflow was triggering the birth of new stars,” Zachary Schutte, Reines’ graduate student and lead author of the new study, says.

“Hubble’s amazing resolution clearly shows a corkscrew-like pattern in the velocities of the gas, which we can fit to the model of a precessing, or wobbling, outflow from a black hole. A supernova remnant would not have that pattern, and so it is effectively our smoking-gun proof that this is a black hole,” Reines adds.

One Step Towards Solving a Persistent Puzzle

How supermassive black holes form continues to be a puzzle for astronomers, and the relationship of Henize 2-10 and its black hole can possibly help provide clues.

“The era of the first black holes is not something that we have been able to see, so it really has become the big question: where did they come from? Dwarf galaxies may retain some memory of the black hole seeding scenario that has otherwise been lost to time and space,” Reines explains.