The event provides evidence for how early supermassive black holes grew so fast.

Key takeaways

  • Astronomers saw matter fall into a black hole at 30% the speed of light for the first time.
  • The black hole is in a Seyfert galaxy one billion light-years away.
  • The falling matter showed no rotation, unlike the surrounding accretion disk.
  • The event supports the theory of “chaotic accretion” where matter falls into black holes from different directions.
  • Chaotic accretion can help supermassive black holes grow quickly and shine brightly in the early universe.

Nothing can escape from a black hole after it has passed the event horizon, or the point of no return. While the depths of black holes will remain a mystery, astronomers may study the zones surrounding them. In a study published in the Monthly Notices of the Royal Astronomical Society, a team of astronomers reported for the first time observing a clump of matter falling directly into a faraway black hole at roughly one-third the speed of light.

The images, made by the European Space Agency’s orbiting XMM-Newton X-ray observatory, are of the 40 million-solar-mass supermassive black hole at the heart of the galaxy PG211+143, located roughly one billion light-years distant. PG211+143 is a Seyfert galaxy, which means it has a brilliant, actively feeding black hole in its core that attracts gas and dust from its environs. By spreading the X-ray radiation received from that material out by wavelength, researchers headed by Ken Pounds of the University of Leicester clocked a clump of matter going into the black hole at 30 percent the speed of light — around 56,000 miles per second (90,000 kilometers per second). “We were able to follow an Earth-sized clump of matter for nearly a day, as it was drawn toward the black hole, accelerating to a third of the velocity of light before being swallowed up by the hole,” said Pounds in a press release.

Peculiarly, the infalling gas showed no rotation — it was not moving in the same way as the larger accretion disk shining around the black hole — from its initial distance at only about 20 times the black hole’s size when it was first spotted.

Chaos rules

The conventional “picture” of a black hole depicts a compact, huge entity at its core, surrounded by a disk of hot gas. This is due to the fact that, because black holes are so tiny in comparison to the mass they contain, infalling matter cannot all be crammed into them at once; instead, it creates a spinning disk, similar to water streaming down a drain, and ultimately approaches the black hole and falls in. As matter flows from the outer disk to the event horizon, it loses gravitational potential energy, which is transformed into observable radiation.

In this classic model, the orbits of material within the accretion disk are considered to match with the spin of the black hole itself, resulting in a single disk. With that in mind, the fact that the infalling matter rotated little is surprising — at least until the introduction of current computer models built at the University of Leicester and ran on the UK’s DiRAC supercomputer facility.

The theory and models account for the fact that matter may fall into a black hole from any direction. Multiple, mismatched accretion disks may develop as matter streams in, rather than simply one. Matter may then “tear” away from these disks, generating rings of material that, when they contact, cancel out their spin, allowing the material to flow directly into the black hole — just as the astronomers observed.

This graphic shows what chaotic accretion might look like: At least two misaligned accretion disks, as well as rings of material that have torn off the disks, surround a supermassive black hole. K. Pounds et al. / University of Leicester

Such a process, known as “chaotic accretion,” may occur in objects such as supermassive black holes in the core of galaxies, which may accrete large quantities of material, especially early in their lifetimes or after close contacts with other galaxies. Chaotic accretion might slow down a supermassive black hole’s spin over time, allowing it to swallow matter more easily and expand swiftly — and shine brilliantly — both of which have been detected in these objects since the early cosmos.

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