Supermassive black holes contain many times the mass of our own sun, but even among this class, one object has to be the smallest of the giants. Now, astronomers believe they have discovered the smallest supermassive black hole known anywhere in the visible Universe.
The dwarf galaxy RGG 118, located about 340 million light-years from Earth, contains the supermassive black hole, which weighs in at a "mere" 50,000 solar masses. Galaxies typically contain supermassive black holes at their centers. Our own Milky Way galaxy contains such an object containing 100 times the mass of the one discovered in the recent finding.
Using the Chandra X-ray Observatory and the 253-inch Clay Telescope, housed in Chile, astronomers carefully examined this unusual object. The team examined data from the Clay Telescope, revealing information on the motion of cool gas near the center of the galaxy. This was then compared with X-ray data detailing hot gas falling into the black hole.
This discovery could help astronomers better understand how supermassive black holes form and develop over time. The oldest of these objects is believed to have formed 13 billion years before our modern day.
"It might sound contradictory, but finding such a small, large black hole is very important. We can use observations of the lightest supermassive black holes to better understand how black holes of different sizes grow," said Vivienne Baldassare, a doctoral student from the University of Michigan.
The supermassive black hole found in the disc galaxy RGG 118 is roughly half the mass of the previous record-holder. The largest supermassive black holes known contain 100,000 times as much "stuff" as the newly-discovered specimen.
Black holes, which form during the deaths of the largest stars in the universe, known as stellar black holes, are still far, far smaller than the objects that lay at the centers of most galaxies.
Astronomers believe that most larger galaxies grew over time, as they absorbed smaller collections of stars over time. This dwarf galaxy has likely never experienced a collision, providing astronomers with a look into what galaxies looked like in the early days of the visible Universe.
"These little galaxies can serve as analogs to galaxies in the earlier universe. For galaxies like our Milky Way, we don't know what it was like in its youth," Baldassare said.
The supermassive black holes at the core of young galaxies swallow massive quantities of matter, unlike relatively tranquil older specimens, such as the one in our own collection of stars.
Discovery of the smallest-known supermassive black hole was profiled in The Astrophysical Journal Letters.
