By Will Dunham
WASHINGTON (Reuters) – At the center of the Milky Way lies a supermassive black hole four million times the mass of our Sun called Sagittarius A*, which some scientists call a gentle giant because of its inactivity. But someday it could become a beast.
Researchers said Tuesday they have observed in real time a dramatic glow at the heart of another galaxy, apparently caused by a supermassive black hole awakening from dormancy and beginning to gorge itself on nearby material. It is the first time this awakening process has been seen to happen.
Earth-based and orbiting telescopes were used to track the events unfolding at the center of a galaxy called SDSS1335+0728, located about 360 million light-years from Earth in the constellation Virgo. A light year is the distance light travels in one year, 5.9 trillion miles (9.5 trillion km).
Black holes are extraordinarily dense objects with gravity so strong that not even light can escape. They range in size from a mass equivalent to a single star to the giants at the center of many galaxies, millions and even billions of times more massive. The supermassive black hole in the galaxy SDSS1335+0728 has a mass about a million times that of the Sun.
The environment around a supermassive black hole can be extraordinarily violent, as it destroys stars and swallows any other material within its gravitational reach. Researchers said it appears that a rotating disk of diffuse material has formed around the supermassive black hole SDSS1335+0728, with some of the matter being consumed. This disk – called an accretion disk – radiates energy at very high temperatures, sometimes outshining an entire galaxy.
A bright, compact region like this, powered by a supermassive black hole at the center of a galaxy, is called an “active galactic nucleus.”
“These nuclei are characterized by emitting large amounts of energy in a variety of wavelengths, from radio to gamma rays. They are considered one of the most luminous objects in the universe,” said astrophysicist Paula Sanchez Saez of the European Southern Observatory, in Germany. lead author of the study published in the journal Astronomy & Astrophysics.
“Studying active galactic nuclei is crucial to understanding the evolution of galaxies and the physics of supermassive black holes,” Sanchez added.
This galaxy, with a diameter of about 52,000 light-years and a mass equivalent to about 10 billion Sun-sized stars, was observed for decades before sudden changes were detected in 2019. The luminosity at the heart of the galaxy has increased in observations. since then.
Supermassive black holes sometimes launch vast jets of high-energy particles into space, but no such jet was detected in this case, according to astrophysicist and study co-author Lorena Hernandez Garcia of Valparaíso University in Chile.
So what could have activated this supermassive black hole?
“Right now, we don’t know,” Sanchez said.
“It could be a natural process in the galaxy,” Hernandez added. “We know that a galaxy goes through different phases of activity and inactivity during its life. Something can happen to activate a galaxy, such as a star falling into a black hole.”
If the observations represented something other than the beginnings of an active galactic nucleus, it would have to be a never-before-seen astrophysical phenomenon, according to the researchers.
Sagittarius A*, or Sgr A*, is located about 26,000 light years from Earth. Could it also suddenly roar to life?
“The same process could eventually happen with Sgr A*, which is actually inactive. But for now we are not at risk and probably if it is activated we won’t notice it because we are too far from the center,” said Hernandez.
(Reporting by Will Dunham, Editing by Rosalba O’Brien)
