Hubble Discovers a Dwarf Galaxy with a Black Hole Igniting Star Formation

Black holes, which are sometimes depicted as deadly creatures that enslave light, take on a less evil role in new research from NASA’s Hubble Space Telescope. Rather than devouring stars, a black hole at the center of the dwarf galaxy Henize 2-10 is creating them.

The black hole appears to be contributing to the galaxy’s current inferno of new star creation. In the southern constellation Pyxis, the dwarf galaxy is 30 million light-years away.

A decade ago, this little galaxy sparked a dispute among astronomers about whether dwarf galaxies harbor supermassive black holes comparable to those found in the centers of larger galaxies.

Little Henize 2-10, which contains only one-tenth the amount of stars seen in our Milky Way, is poised to play a key role in answering the enigma of where supermassive black holes arose from in the first place, thanks to this new discovery. NASA and the European Space Agency collaborated on the Hubble Space Telescope (European Space Agency).

The telescope is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Hubble science operations are managed by the Space Telescope Science Institute (STScI) in Baltimore, Maryland. The Association of Universities for Research in Astronomy in Washington, D.C. manages STScI for NASA.

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.

Amy Reines

“Ten years ago, as a graduate student thinking I would spend my career on star formation, I looked at the data from Henize 2-10 and everything changed,” said Amy Reines, who published the first evidence for a black hole in the galaxy in 2011 and is the principal investigator on the new Hubble observations, 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 said.

That link is a gas outflow from a brilliant star nursery that stretches across space like an umbilical cord. When the low-velocity outflow came, the region already had a dense cocoon of gas.

According to Hubble spectroscopy, the outflow was travelling at around 1 million miles per hour, striking against the dense gas and spreading out like a garden hose hitting a pile of dirt. Newborn star clusters dot the course of the outflow’s propagation, with Hubble calculating their ages as well.

This is the polar opposite of what happens in larger galaxies, where material falling toward the black hole is swept away by the surrounding magnetic fields, resulting in scorching jets of plasma flying at near-light speed.

Gas clouds caught in the path of the jets would be heated to the point where they couldn’t cool down and create stars. The less-massive black hole in Henize 2-10, on the other hand, had a softer outflow, allowing gas to be compressed just enough to cause fresh star formation.

“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,” said Zachary Schutte, Reines’ graduate student and lead author of the new study.

Reines had assumed that the peculiar radio and X-ray emissions in Henize 2-10 emanated from a giant black hole, but not as supermassive as those detected in larger galaxies, since she first discovered them.

Other astronomers, on the other hand, believed the radiation was coming from a supernova remnant, which would be a common event in a galaxy that is fast producing enormous stars that explode.

“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 said.

Dwarf galaxy black holes, according to Reines, will be the subject of even more investigation in the future, with the goal of using them as clues to the puzzle of how supermassive black holes formed in the early cosmos. Astronomers have been pondering this question for a long time.

The link between the galaxy’s mass and its black hole can reveal information. Henize 2-10’s black hole has a mass of about a million solar masses. Black holes in larger galaxies can be more than a billion times the mass of our Sun. The core black hole grows in size as the host galaxy grows in size.

Current theories on the origin of supermassive black holes break down into three categories: they formed just like smaller stellar-mass black holes, from the implosion of stars, and somehow gathered enough material to grow supermassive,

special circumstances in the early cosmos enabled the birth of supermassive stars, which immediately collapsed to generate gigantic black hole “seeds”,

future supermassive black holes were conceived in dense star clusters, where the cluster’s entire mass would have been sufficient to produce them through gravitational collapse.

So far, none of these black hole seeding hypotheses has emerged as the most compelling. Because dwarf galaxies, such as Henize 2-10, have remained small across cosmic time rather than growing and merging like the Milky Way, they offer promising prospective clues. Dwarf galaxy black holes, according to astronomers, could represent analogs for black holes in the early universe, when they were only starting to form and grow.

“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 said.

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