Black holes are often described as the monsters of the universe - tearing stars apart, consuming everything that comes too close, and keeping the light trapped. However, detailed evidence from NASA's Hubble Space Telescope shows a black hole in a new light: Promoting rather than suppressing star formation. Hubble imaging and spectroscopy of the dwarf star eruption galaxy Henize 2-10 clearly show a gas outflow extending from the black hole to a luminous star-bearing region like an umbilical cord, triggering the already dense cloud to form clusters of stars. Astronomers have previously discussed that a dwarf galaxy could have a black hole analogous to the supermassive black holes in larger galaxies. Further studies of dwarf galaxies, which have remained small over cosmic times, may shed light on the question of how the first seeds of supermassive black holes formed and evolved over the course of the universe's history.
Often portrayed as destructive monsters holding light trapped, black holes occupy a minor role in recent research from NASA's Hubble Space Telescope. A black hole in the heart of the dwarf galaxy Henize 2-10 creates stars instead of swallowing them. The black hole apparently contributes to the firestorm of new star formation taking place in the galaxy. The dwarf galaxy is 30 million light-years away, in the southern constellation Pyxis.
A decade ago, this small galaxy sparked debate among astronomers as to whether dwarf galaxies were home to black holes proportional to the supermassive giants found in the hearts of larger galaxies. This new discovery has little Henize 2-10, which contains only a tenth of the number of stars found in our Milky Way, ready to play a major role in solving the mystery of where supermassive black holes came from in the first place.
"Ten years ago, when I, as a graduate student, thought 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 proof of a black hole in the galaxy in 2011 and is the lead investigator of 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 given 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 connection is an outflow of gas that extends across space like an umbilical cord to a bright star nursery. The region was already home to a dense cocoon of gas when the low-velocity outflow arrived. Hubble spectroscopy shows that the effluent moved about 1 million miles per hour, slamming into the dense gas like a garden hose hitting a pile of dirt and spreading. Newborn star clusters puncture the path of the outflow spread, their age is also calculated by Hubble.
This is the opposite effect of what is seen in larger galaxies, where material falling towards the black hole is carried away by the surrounding magnetic fields and forms flaming plasma rays that move close to the speed of light. Gas clouds trapped in the jets would be heated far beyond their ability to cool down again and form stars. But with the less massive black hole in Henize 2-10, and its milder outflow, gas was compressed just enough to precipitate new star formation.
"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 further surprise was that instead of suppressing star formation, the outflow was triggers the birth of new stars, "said Zachary Schutte, Reines' graduate student and lead author of the new study.
Ever since her first discovery of characteristic radio and X-rays in Henize 2-10, Reines has thought they probably came from a massive black hole, but not as supermassive as those seen in larger galaxies. Other astronomers, however, believed that the radiation was more likely emitted by a supernova remnant, which would be a well-known event in a galaxy that quickly pumps out massive stars that quickly explode.
"Hubble's stunning resolution clearly shows a corkscrew-like pattern in gas velocities that we can adapt to the model of a preceding or wobbly outflow from a black hole. A supernova remnant would not have that pattern, and so it is actually ours. smoking weapons proof that this is a black hole, "Reines said.
Reines expects that even more research will be directed at the black holes of dwarf galaxies in the future with the aim of using them as clues to the mystery of how supermassive black holes came to be in the early universe. It is an enduring puzzle for astronomers. The relationship between the mass of the galaxy and its black hole can leave traces. The black hole in Henize 2-10 is about 1 million solar masses. In larger galaxies, black holes can be more than 1 billion times the mass of our Sun. The more massive the host galaxy, the more massive the central black hole.
Current theories about the origin of supermassive black holes are divided into three categories: 1) they are formed like smaller star-mass black holes, from the implosion of stars, and somehow collected enough material to grow supermassive, 2 ) special conditions in the early universe allowed the formation of supermassive stars, which collapsed to form massive black hole "seeds" just outside the bat, or 3) the seeds of future supermassive black holes were born in dense star clusters, where the total mass of the cluster would have been enough to somehow create them from gravitational collapse.
So far, none of these black hole-seed theories have taken the lead. Dwarf galaxies like Henize 2-10 offer promising potential traces because they have remained small over cosmic time, rather than having undergone the growth and merging of large galaxies like the Milky Way. Astronomers believe that the black holes of the dwarf galaxy could serve as an analogue to black holes in the early universe, as they had just begun to form and grow.
"The era of the first black holes is not something we've been able to see, so it's really become the big question: Where did they come from? Dwarf galaxies can preserve a memory of the black hole sowing scenario that has otherwise been "lost to time and space," Reines said.
Citation: Hubble finds a black hole that ignites star formation in a dwarf galaxy (2022, January 19) retrieved January 19, 2022 from https://phys.org/news/2022-01-hubble-black-hole-igniting-star. html
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