Supermassive black hole spins at nearly the speed of light

This artist’s concept illustrates a supermassive black hole with millions to billions times the mass of our sun. It’s surrounded by matter flowing onto the black hole in what is termed an accretion disk. Also shown is an outflowing jet of energetic particles, believed to be powered by the black hole’s spin. High energy X-radiation lights up the disk, which reflects it, making the disk a source of X-rays. The reflected light enables astronomers to see how fast matter is swirling in the inner region of the disk, and ultimately to measure the black hole’s spin rate.

Nothing can escape a black hole, even light, because to wrench away from its titanic gravitational pull, you’d have to move faster than light is capable of traveling. And nothing can do that, as far as anyone knows. As matter falls into a black hole’s gaping maw, it superheats to millions of degrees, screaming a final cry of X-rays as it is torn apart. At a specific point called an event horizon, the matter disappears and is never heard from again.

A pair of X-ray telescopes recently watched some of these X-ray death gasps and were able to figure out how fast a black hole is spinning. This is “hugely important” for black hole science, according to researchers working with NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR space telescope. One particularly cool finding: The black hole is spinning almost as fast as Einstein’s theory of gravity says it possibly could. It’s spinning at almost the speed of light.

The galaxy in question is called NGC 1365, which is about twice the size of the Milky Way and located about 60 million light years away. The black hole is about 2 million times more massive than the sun. Scientists using NuSTAR and the European Space Agency’s XMM-Newton satellite wanted to measure how fast it is spinning. This is a key feature of black holes that is related to their size and the way they gobble up stars, gas and even other black holes.

The problem is that black holes are hard to study, because, you know, not even light can escape them. To measure them, you have to measure their effect on their surroundings–like the X-rays emitted by dying matter. This is hard to do because objects between us and them can get in the way, however, making the X-rays look distorted. There have been two competing models explaining why the X-rays look warped: Either gravitational distortion caused by black hole gravity, or distortion caused by intervening clouds of gas and dust.

In this new study, NuSTAR and XMM-Newton set out to determine which one is right. The telescopes carefully traced the X-rays emitted at the very, very edge of the black hole, right near the event horizon, or the point of no return. By combining their distinct viewing abilities, the two telescopes were able to see a wide range of X-ray energies, and figure out that the X-rays are not actually distorted by intervening gas clouds. They look distorted because the black hole is spinning, and its immense gravity warps spacetime as it swirls around. This information was used to tell just how fast the black hole is spinning: Just below the universal speed limit.

Along with new information about this particular black hole, this study suggests that black hole observations can remove a little bit of ambiguity. This will help astronomers continue to unravel the mysteries of these galactic monsters. A paper describing the findings is published last week in Nature.

What hyperspace would really look like


The science fiction vision of stars flashing by as streaks when spaceships travel faster than light isn’t what the scene would actually look like, a team of physics students says.

Instead, the view out the windows of a vehicle traveling through hyperspace would be more like a centralized bright glow, calculations show.

The finding contradicts the familiar images of stretched out starlight streaking past the windows of the Millennium Falcon in “Star Wars” and the Starship Enterprise in “Star Trek.” In those films and television series, as spaceships engage warp drive or hyperdrive and approach the speed of light, stars morph from points of light to long streaks that stretch out past the ship.

But passengers on the Millennium Falcon or the Enterprise actually wouldn’t be able to see stars at all when traveling that fast, found a group of physics Masters students at England’s University of Leicester. Rather, a phenomenon called the Doppler Effect, which affects the wavelength of radiation from moving sources, would cause stars’ light to shift out of the visible spectrum and into the X-ray range, where human eyes wouldn’t be able to see it, the students found.

“The resultant effects we worked out were based on Einstein’s theory of Special Relativity, so while we may not be used to them in our daily lives, Han Solo and his crew should certainly understand its implications,” Leicester student Joshua Argyle said in a statement.

The Doppler Effect is the reason why an ambulance’s siren sounds higher pitched when it’s coming at you compared to when it’s moving away — the sound’s frequency becomes higher, making its wavelength longer, and changing its pitch.

The same thing would happen to the light of stars when a spaceship began to move toward them at significant speed. And other light, such as the pervasive glow of the universe called the cosmic microwave background radiation, which is left over from the Big Bang, would be shifted out of the microwave range and into the visible spectrum, the students found.

“If the Millennium Falcon existed and really could travel that fast, sunglasses would certainly be advisable,” said research team member Riley Connors. “On top of this, the ship would need something to protect the crew from harmful X-ray radiation.”

The increased X-ray radiation from shifted starlight would even push back on a spaceship traveling in hyperdrive, the team found, slowing down the vehicle with a pressure similar to the force felt at the bottom of the Pacific Ocean. In fact, such a spacecraft would need to carry extra energy reserves to counter this pressure and press ahead.

Whether the scientific reality of these effects will be taken into consideration on future Star Wars films is still an open question.

“Perhaps Disney should take the physical implications of such high speed travel into account in their forthcoming films,” said team member Katie Dexter.

Connors, Dexter, Argyle, and fourth team member Cameron Scoular published their findings in this year’s issue of the University of Leicester’s Journal of Physics Special Topics.