Can the death of one star give birth to two black holes?

black holes merge

Credit: NASA

Two weeks ago, astronomers announced the first ever detection of gravitational waves. The detected signal was generated by the merging of two stellar black holes. Stellar black holes are formed when a star runs out of fuel (the fusion of hydrogen into helium) and its centre collapses under its own gravity, causing a supernova explosion. Now a recent paper by astrophysicist Avi Loeb, of the Harvard-Smithsonian Center for Astrophysics, claims that two black holes can form out of the same dying star.

If indeed, one star can give birth to two black holes, a gamma-ray burst might also be produced. Such an event was observed; using the Fermi Gamma-ray Space Telescope, only 0.4 seconds after the gravitational signal was detected. Whether this signal is real and is associated with the black hole merger that generated the detected gravitational waves, is still under investigation. Even if the signal is false or not associated with black hole merger this does not necessarily mean that Loeb’s hypothesis is wrong. Future detections of other similar events that involve twin black holes will allow us to check if two black holes can be created from the death of a single star.



Publication: Loeb 2016