Black Hole Light Show

It is known that black holes can be slow time for a crawl and tidally stretch large objects in spaghetti-like strands. However, according to new theoretical research of two NASA astrophysicist, the wrenching gravity just outside the outer limit of a black hole is yet another bizarre effect: light echoes.

"The light echoes come because of the severe warping of space-time predicted by Einstein," says KEIGO Fukumura of NASA's Goddard Space Flight Center. "If the black hole spins quickly, it can literally drag the surrounding space, and this may take some wild special effects."
Many black holes are surrounded by disks searing hot gas, swirl around to almost the speed of light. Hot spots within these sheets sometimes encounter random bursts of X-rays, which have been identified by an orbiting X-ray observatories. But after Fukumura and his colleague, Demosthenes Kazanas, things get interesting if they take account of Einstein's general theory of relativity, which describes how extremely massive objects like black holes actually chain and drag the surrounding space-time.

Many of these X-ray photons travel to Earth by different paths around the black hole. Because the black hole of the extreme gravity warps the surrounding space-time, it prevents the flight paths of the photons so that they come here with a lag, depending on the relative positions of the X-ray flare, the black hole, and the earth.
But if the black hole rotates very fast, then Fukumura and Kazanas calculations, the delay between the photons is constant, regardless of the source position. They discovered that the rapidly spinning black holes, about 75 percent of the X-ray photons arrive in the Observer after completing a fraction of an orbit around the black hole, while the remaining photons travel the exact same fraction of plus one or more full - Railways.

"For every X-ray burst from a hot spot, the observers will be two or more flashes, separated by a constant distance, so that a signal from a totally random collection of bursts of hot spots in various positions itself contains an echo" Kazanas says.
Although difficult to see the raw data, astronomers can a Fourier analysis or other statistical methods to collect these hidden echoes. Among other things, a Fourier analysis is a mathematical tool for extracting periodic behavior on a signal that would otherwise seem totally random. The echoes seems as quasi-periodic oscillations (QPOs). An example of a QPO with a period of 10 seconds could exhibit peaks at 9, 21, 30, 39, 51 and 61 seconds.

If you consider a 10-solar-mass black hole, that a dying star, and if the black hole spins more than 95 percent of the maximum possible speed, the period of his QPOs would be about 0.7 milliseconds, which corresponds to about 1400 peaks per second, three times higher than any QPOs that have been observed around black holes. NASA's Rossi X-ray Timing Explorer satellite could such a measure high-frequency QPOs, but the signal would have to be very strong.
Detecting these high-frequency QPOs would do more than just another confirmation of the prediction of Einstein's theory. It would be a real treasure trove of information about the Black Hole. The frequency of QPOs depends on the black hole mass, so that the recognition of this echo effect would give astronomers an accurate way to measure the mass of black holes. In addition, notes Kazanas, "This echoes only occur if a black hole is spinning near their maximum speed possible so that it now say that the astronomers the black hole spins really fast."