Washington, Jan 11 : A new theoretical research from two NASA astrophysicists has suggested that the wrenching gravity just outside the outer boundary of a black hole can produce an effect known as light echoes, as predicted by Albert Einstein.
Keigo Fukumura and his colleague Demosthenes Kazanas from the Goddard Space Flight Center carried out the research.
"The light echoes come about because of the severe warping of spacetime predicted by Einstein," said Keigo Fukumura of NASA's Goddard Space Flight Center in Greenbelt, Md. "If the black hole is spinning fast, it can literally drag the surrounding space, and this can produce some wild special effects," he added.
Many black holes are surrounded by disks of searing hot gas that whirl around at nearly the speed of light. Hot spots within these disks sometimes emit random bursts of X-rays, which have been detected by orbiting X-ray observatories.
But according to Fukumura and Kazanas, things get more interesting when they take into account Einstein's general theory of relativity, which describes how extremely massive objects like black holes can actually warp and drag the surrounding space-time.
"For each X-ray burst from a hot spot, the observer will receive two or more flashes separated by a constant interval, so even a signal made up from a totally random collection of bursts from hot spots at different positions will contain an echo of itself," said Kazanas.
Though difficult to discern in the raw data, astronomers can use a Fourier analysis, or other statistical methods, to pick up these hidden echoes, which would appear as quasi-periodic oscillations (QPOs).
The detection of these QPOs would also provide much information about the black hole itself.
Because the frequency of the QPOs depends on the black hole's mass, detecting this echo effect would give astronomers an accurate way to measure the masses of black holes.
"This echoes occur only if a black hole is spinning near its maximum possible speed, so it would tell astronomers that the black hole is spinning really fast," said Kazanas.