A star about 8,500 light-years away from us, spinning so fast that its surface velocity is more than 620,000 mph! It also has a strange companion, a Black hole.
Above: The Be star known as MWC 656 spins at extremely high velocity, with a mass between 3.8 and 6.9 solar masses, ejecting matter through an equatorial disk. Part of this matter falls on to the black hole forming an accretion disk. Image © Gabriel Pérez – SMM (IAC)
Astronomers are familiar with these kinds of stars, but Spanish scientists discovered the first binary system ever known to consist of a “spinning” star and a black hole.
Marc Ribó from the Science Institute of the Cosmos at Barcelona University, said:
“We started studying this star back in 2010 when space telescopes detected transient gamma-ray emission coming from its direction. No more gamma-ray emission has subsequently been detected, but we found that the star was part of a binary system.”
Ignasi Ribas of CSIC at the Institute of Space Sciences, said:
“It turned out to be an object with a mass between 3.8 and 6.9 solar masses. An object like that, invisible to telescopes and with such large mass, can only be a black hole because no neutron star with more than three solar masses can exist.”
Ignacio Negueruela at the University of Alicante, said:
“The high rotation speed of the Be star causes matter to be ejected into an equatorial disk. This matter is attracted by the black hole and falls on to it, forming another disk, called an accretion disk. By studying the emission from the accretion disk, we could analyze the motion of the black hole and measure its mass.”