AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
Charmas baylock8/6/2023 “It’s clogged up to a little trickle,” said Priya Natarajan, a cosmologist at Yale University, comparing the galaxy to a broken showerhead. Somehow only a thousandth of the matter that’s flowing into the Milky Way from the surrounding intergalactic medium makes it all the way down and into the hole. “That’s revealing a huge problem,” Natarajan said. “Where is this gas going? What is happening to the flow? It’s very clear that our understanding of black hole growth is suspect.” Over the past quarter century, astrophysicists have come to recognize what a tight-knit, dynamic relationship exists between many galaxies and the black holes at their centers. “The surprise was that black holes are important as shapers and controllers of how galaxies evolve.” “There’s been a really huge transition in the field,” says Ramesh Narayan, a theoretical astrophysicist at Harvard University. These giant holes - concentrations of matter so dense that gravity prevents even light from escaping - are like the engines of galaxies, but researchers are only beginning to understand how they operate. Gravity draws dust and gas inward to the galactic center, where it forms a swirling accretion disk around the supermassive black hole, heating up and turning into white-hot plasma. ![]() Then, when the black hole engulfs this matter (either in dribs and drabs or in sudden bursts), energy is spat back out into the galaxy in a feedback process. “When you grow a black hole, you are producing energy and dumping it into the surroundings more efficiently than through any other process we know of in nature,” said Eliot Quataert, a theoretical astrophysicist at Princeton University. This feedback affects star formation rates and gas flow patterns throughout the galaxy.īut researchers have only vague ideas about supermassive black holes’ “active” episodes, which turn them into so-called active galactic nuclei (AGNs). “What is the triggering mechanism? What is the off switch? These are the fundamental questions that we’re still trying to get at,” said Kirsten Hall of the Harvard-Smithsonian Center for Astrophysics. Stellar feedback, which occurs when a star explodes as a supernova, is known to have similar effects as AGN feedback on a smaller scale. These stellar engines are easily big enough to regulate small “dwarf” galaxies, whereas only the giant engines of supermassive black holes can dominate the evolution of the largest “elliptical” galaxies. Size-wise, the Milky Way, a typical spiral galaxy, sits in the middle. With few obvious signs of activity at its center, our galaxy was long thought to be dominated by stellar feedback. Jackson was seen as a more established star at the time.But several recent observations suggest that AGN feedback shapes it as well.
0 Comments
Read More
Leave a Reply. |