The two giant black holes that were first detected by Laser Interferometer Gravitational-wave Observatory (LIGO) scientists last year may have been part of a massive star, which generated a burst of gamma rays throughout space when it died.
In a study featured in The Astrophysical Journal Letters, researchers from the Harvard-Smithsonian Center for Astrophysics (CfA) studied how the pair of giant black holes, with masses several times greater than that of the Sun, came to be formed in space.
Formation Of The Twin Black Holes
When a massive star is about to die, its core typically collapses to form a single black hole. However, if the star was spinning at a very fast rate just before it dies, the core could potentially stretch to form a shape similar to a dumbbell and break down into two large fragments. These fragments would then go on to turn into black holes.
Avi Loeb, an astrophysicist from the CfA, likened it to a pregnant woman who is carrying twin babies in her womb.
According to the researchers, the massive star that gave birth to the two black holes could itself have been born from the combination of two smaller stars. These smaller objects likely revolved around each other at continuously increasing rates that by the time they merged, the resulting single giant star spun at a very fast rate as well.
When the two black holes came about, they caused the outer envelope of the parent star to be sucked in toward them.
Loeb and his colleagues believe that for the gravitational wave event that LIGO observed, and the burst of gamma rays that the Fermi Space Telescope detected to occur, the two black holes were likely born very close to each other - coming together within mere minutes.
The resulting single massive black hole proceeded to feed on all of the matter surrounding it. The researchers estimate that it was able to consume material equivalent to the Sun's mass each second, causing it to release jets of matter that turned into the gamma-ray burst.
The Fermi Space Telescope was able to detect the gamma-ray burst 0.4 seconds after LIGO's detection of the gravitational waves. Both of these energy signatures came from the same region of space.
The ESA's International Gamma-Ray Astrophysics Laboratory satellite, however, was unable to confirm the signal from the burst.
"Even if the Fermi detection is a false alarm, future LIGO events should be monitored for accompanying light irrespective of whether they originate from black hole mergers," Loeb pointed out. "Nature can always surprise us."
The researchers hope that they will be able to detect more bursts similar to those of the gamma rays from the merging of two black holes. They can use such events to measure the distances of objects across space.
Loeb said that astrophysical black holes are easier to use as indicators of distance in space compared to others such as supernovae. This is because black holes can be fully defined by measuring their spin and mass.
