Super Massive Black Hole's Spin Revealed for the First Time

According to a news release from the Harvard-Smithsonian Center for Astrophysics.,"The Nuclear Spectroscopic Telescope Array (NuSTAR) has spotted a super massive black hole spinning so fast that its surface is traveling at nearly the speed of light".


Astronomers measured its AMAZING jaw-dropping spin rate using new data from the Nuclear Spectroscopic Telescope Array, or NuSTAR, and the European Space Agency's XMM-Newton X-ray satellites.

"This is the first time anyone has accurately measured the spin of a super massive black hole," said lead author Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics (CfA) and INAF - Arcetri Observatory.

Super Massive Black Hole's Spin Revealed for the First Time

The study’s findings as published in the journal Nature.


A black hole's gravity is so strong that, as the black hole spins, it drags the surrounding space along. The edge of this spinning hole is called the event horizon. Any material crossing the event horizon is pulled into the black hole. Inspiraling matter collects into an accretion disk, where friction heats it and causes it to emit X-rays.

Risaliti and his colleagues measured X-rays from the center of NGC 1365 to determine where the inner edge of the accretion disk was located. This Innermost Stable Circular Orbit - the disk's point of no return - depends on the black hole's spin. Since a spinning black hole distorts space, the disk material can get closer to the black hole before being sucked in.

Astronomers want to know the black hole's spin for several reasons. The first is physical - only two numbers define a black hole: mass and spin. By learning those two numbers, you learn everything there is to know about the black hole.

Most importantly, the black hole's spin gives clues to its past and by extension the evolution of its host galaxy.
"The black hole's spin is a memory, a record, of the past history of the galaxy as a whole," explained Risaliti.
Although the black hole in NGC 1365 is currently as massive as several million Suns, it wasn't born that big. It grew over billions of years by accreting stars and gas, and by merging with other black holes.
Spin results from a transfer of angular momentum, like playing on a children's swing. If you kick at random times while you swing, you'll never get very high. But if you kick at the beginning of each downswing, you go higher and higher as you add angular momentum.

Similarly, if the black hole grew randomly by pulling in matter from all directions, its spin would be low. Since its spin is so close to the maximum possible, the black hole in NGC 1365 must have grown through "ordered accretion" rather than multiple random events.

Studying a supermassive black hole also allows theorists to test Einstein's general theory of relativity in extreme conditions. Relativity describes how gravity affects the structure of space-time, and nowhere is space-time more distorted than in the immediate vicinity of a black hole.

The team also has additional observations of NGC 1365 that they will study to determine how conditions other than black hole spin change over time. Those data are currently being analyzed. At the same time, other teams are observing several other supermassive black holes with NuSTAR and XMM-Newton.



Photo credit: NASA/JPL-Caltech

Going To Mars Could Damage The Brains Of Astronauts

According to lead researcher M. Kerry O’Banion in a press release, ”Galactic cosmic radiation poses a significant threat to future astronauts. The possibility that radiation exposure in space may give rise to health problems such as cancer has long been recognized. However, this study shows for the first time that exposure to radiation levels equivalent to a mission to Mars could produce cognitive problems and speed up changes in the brain that are associated with Alzheimer’s disease.”

As part of the study, the researchers exposed mice with known timeframes for developing Alzheimer’s to the type of low-level radiation that astronauts would be exposed to over time on a long space journey. The mice were then put through tests that measured their memory and cognitive ability. The mice that were exposed to radiation showed significant cognitive impairment.

Going To Mars Could Damage The Brains Of Astronauts

The mice also showed physical signs of degradation. An examination of their brains showed differences in blood flow in their brain. Also, the mice exposed to radiation showed larger plaques of the type seen with Alzheimer’s patients.

“These findings clearly suggest that exposure to radiation in space has the potential to accelerate the development of Alzheimer’s disease,” said O’Banion. ”This is yet another factor that NASA, which is clearly concerned about the health risks to its astronauts, will need to take into account as it plans future missions.”

It’s not going to be an easy problem to solve, either. The radiation the researchers used in their testing is composed of highly charged iron particles, which are relatively common in space. Due to their size and energy, those particles can pass through the walls of a spaceship. Shielding from that radiation is no simple task.

“Because iron particles pack a bigger wallop it is extremely difficult from an engineering perspective to effectively shield against them,” said O’Banion. “One would have to essentially wrap a spacecraft in a six-foot block of lead or concrete.”