Research using data from the largest survey of black holes, published in the latest edition of the Astrophysical Journal, indicates that materials such as dust and gas in their vicinity play a critical role in their evolution.
The supermassive black hole at the center of our Milky Way galaxy, known as Sagittarius A*, has a mass equivalent to that of four million suns. Discovered in the 1970s and recently studied thanks to the Event Horizon Telescope, has allowed astronomers to theorize that all galaxies, or at least the most massive ones, have a supermassive black hole at their center: in some cases such black holes can eat material from their surroundings and emit large amounts of energy. These objects are known as active galaxy nuclei or AGN.
The comparison of our Sagittarius A* with the supermassive black hole of the galaxy M87, the first black hole photographed in 2019, reveals that despite the colossal size of our black hole, it is a thousand times smaller and less massive than that of the aforementioned galaxy located 55 million light-years from our planet and whose mass reaches nothing less than that of 6 billion suns. But how do they grow in this way? What causes these differences in their sizes?
While it is known that they are capable of devouring stars – those unfortunate enough to fall under their powerful gravitational pull – new research published by CATA astronomers in the Astrophysical Journal reveals that the dust and gas surrounding these powerful galactic objects plays a key role. “We focused on the relationship between black holes and the material around them that feeds them,” explains Claudio Ricci, an astronomer at Diego Portales University and CATA who led the research.
To achieve this, the scientists used data from the largest survey of black holes in the near or local universe, created by the international scientific team of the BASS project, which for more than 15 years has been investigating the active nuclei of galaxies, including an outstanding participation of astronomers from the Center for Astrophysics and Related Technologies (CATA) from Chile. “What we have discovered is that the amount of accreting (growing) black holes decreases when there is less gas and dust around them, and that this material disappears due to the effect of the black hole’s radiation, which pushes it away,” says the astronomer.
About the main image: Active galactic nucleus (credit ESO): Artist’s impression of the active nucleus of a galaxy, surrounded by an accretion disk composed of dust and gas.