- Researchers observed a billion light-year distant galaxy named PG211+143.
- Like other galaxies, it has a supermassive black hole in the center.
- They detected matter falling into this black hole at an extremely fast speed of nearly 90,000,000 meters per second.
Black holes have an enormously strong gravitational field, so strong that even light cannot escape. They provide an effective technique of extracting energy from matter, and thus they are one of the most crucial objects in astronomy.
It has now been proven that a supermassive black hole lies in the center of most galaxies. These black holes have masses between millions and billions of times the solar mass. With enough matter dragging towards them, they can become highly luminous, and are observed as an active galactic nucleus or a quasar.
Instead of directly falling into a black hole, the matter (either in solid or gaseous form) slowly approaches through an accretion disc, which is a series of circular orbits reducing in size. The speed and temperature of matter increase as it spirals inwards. Eventually, it gets hot enough to glow, transforming gravitational energy into radiation that is observed by astronomers.
Recently, researchers at the University of Leicester and Keele University in the UK, observed a billion light-year distant galaxy named PG211+143 using the ESA’s XMM-Newton space observatory. Like other galaxies, it has a supermassive black hole in the center. They detected matter falling into this black hole at 30% of the speed of light.
It’s is considered that matter’s orbit is aligned with the black hole’s rotation, but there’s no solid evidence for this. Until now it hasn’t been clear how (mis)aligned rotation affects the in-fall of isolated stars or interstellar gas clouds. Since they can fall in from any direction, it’s specifically relevant to the feeding of black holes.
What They Actually Observed?
The PG211+143 galaxy is more than one billion light-year far from Earth in the direction of Coma Berenices constellation. It’s a Seyfert galaxy (bright compact core) characterized by an active galactic nucleus that results from the accretion of matter by a supermassive black hole at the center of the galaxy.
Researchers observed the X-ray spectra from this galaxy, using XMM-Newton (X-ray Multi-Mirror Mission) space observatory that was launched by the European Space Agency in 1999.
They discovered that the spectra were highly red-shifted, indicating the matter is falling into the black at an extremely fast speed of nearly 90,000,000 meters per second. At the event horizon — a boundary where nothing can escape black hole’s gravity — the matter has almost zero rotation.
Simulation of a misaligned disc around a black hole | Courtesy of researchers
Researchers also simulated that the distortion of misaligned accretion discs on DiRAC supercomputer. It shows that rings of matter could easily break off and cancel out their rotation by colliding with each other before directly falling into the black hole. These reading closely agrees with recent theoretical studies.
Authors stated that they followed an Earth-sized cluster of matter for almost 24 hours, as it was dragging into the black hole. It accelerated up to 30% of light speed before being engulfed by the black hole.
The observations indicate that misaligned or ‘chaotic’ accretion might be common in supermassive black holes. If this is the case, the black holes’ spin would remain low and they would be able to accumulate far more matter and increase their masses more quickly than previously thought. This explains why some black holes formed in the early Universe rapidly gained huge masses.
Looking ahead, X-ray spectra obtained over several sight lines with high resolution and cadence provide a new way of mapping the fine structure of ionized flows and accretion close to supermassive black holes. The new data offers the best opportunity to further explore the physics of accretion discs and black hole growth in active galactic nuclei.