Using the Hubble Space Telescope, astronomers have for the first time ever mapped the plasma burps of a feeding black hole-powered quasar relatively close to Earth.
Although supermassive black holes with masses millions or billions of times greater than the Sun are thought to live at the heart of all galaxies, not all of these cosmic titans power quasars. Some, like the supermassive black hole at the heart of the Milky Way, called Sagittarius A*, are relatively quiet because they don’t feed greedily on the matter around them.
This particular quasar and the voracious supermassive black hole that powers it are located at the active heart of the Zwicky 1 galaxy, about 847 million light-years from Earth toward the constellation Pisces. Although this is an incredibly large distance, most quasars exist in the early universe, meaning they could be billions of light years away.
The proximity of this quasar, named ‘I Zwicky 1’, thus makes it an excellent laboratory for studying the extreme conditions surrounding active galactic nuclei (AGN), regions so bright that they contain the combined light of every star in the can surpass surrounding galaxies. them. This also applies to the ‘burps’ or outflows of matter from the environment of the supermassive black hole.
The supermassive black hole at the heart of Zwicky 1 is estimated to have a mass equivalent to 9.3 million suns. It is thought to consume matter at an incredible rate, producing powerful jets that cause ‘burps’ at high speed. A team of astronomers from the Netherlands Institute for Space Research (SRON) has described these outflows for the first time.
“I Zwicky 1 is very special in terms of its features,” team leader Anna Juráňová said in a statement. ‘Other quasars have similar outflows, but in this one everything fits exactly. Our viewing angle, the width of the lines in the spectrum, and so on. This allows us to dig much deeper into its processes. We have a global view of the movements of the ionized gas in a quasar, which is rare.”
How quasars get their outflows
Like all black holes, supermassive black holes are surrounded by an outer boundary called the event horizon. This is the point at which a black hole’s gravitational influence has become so intense that not even light is fast enough to match its escape velocity.
Since nothing with mass can travel faster than the speed of light, you might wonder how these outflows can escape quasars. The answer is that the material that makes up the outflows never crosses the event horizon.
When a supermassive black hole is surrounded by matter, whether it is gas and dust or the remains of a star that has torn the black hole apart by its enormous gravity, that matter has angular momentum. This means that it cannot fall directly to the black hole, but instead forms a rotating flat cloud around the black hole, called an ‘accretion disk’.
Matter in the accretion disk is gradually fed toward the central supermassive black hole, but if there’s one thing scientists know about black holes, it’s that they’re messy eaters. Not all matter in accretion disks is destined to fall into the black hole; some charged particles are guided to the poles by powerful magnetic fields.
These magnetic fields accelerate the trapped particles to speeds that are a significant fraction of the speed of light, and are then blown out as highly collimated jets. These jets and the radiation associated with them push out clouds of matter around the supermassive black hole, and these are the outflows that the team for I Zwicky 1 mapped.
Using Hubble, Juráňová and colleagues discovered the properties of four different outflows of plasma around I Zwicky 1. They found that they were traveling at speeds between 217,000 km per hour (134,000 mph), 200 times the speed of sound, and as much as 6.5 million mph. (10.5 million km per hour), which is about 8,500 times the speed of sound and about 1% of the speed of light.
The team also found that one of the outflows appears to be “caught in the shadow” of another from the black hole belch. This happens because radiation from the accretion disk in the form of ultraviolet light is absorbed by elements such as nitrogen, oxygen and carbon in clouds of matter near the black hole and is therefore pushed away.
Not only is this the first time astronomers have seen this mechanism in action, but it also reveals to researchers that the immediate environment of I Zwicky 1 is more active than the AGN houses of other quasars.
“Our data suggests that much more gas is being lifted and blown out of the disk around the black hole,” Juráňová concluded. “Having this insight brings us closer to unraveling how these supermassive black holes grow and interact with their environment.”
The team’s research was published online Tuesday (June 11) in the journal Astronomy & Astrophysics.