New York, April 21 (IANS): As two galaxies enter the final stages of merging, their supermassive black holes form a “binary” or two black holes that are gravitationally bound to one another. Now, astronomers from University of Maryland have found direct evidence of a pulsing quasar which may substantiate the existence of black hole binaries.

“We believe we have observed two supermassive black holes in closer proximity than ever before,” said Suvi Gezari, assistant professor of astronomy.

This pair of black holes may be so close together that they are emitting gravitational waves, which were predicted by Einstein's theory of general relativity.

The discovery could shed light on how often black holes get close enough to form a gravitationally bound binary and eventually merge together.

Black holes typically gobble up matter, which accelerates and heats up, emitting electromagnetic energy and creating some of the most luminous beacons in the sky called quasars.

When two black holes orbit as a binary, they absorb matter cyclically, leading theorists to predict that the binary's quasar would respond by periodically brightening and dimming.

The astronomers found quasar PSO J334.2028 01.4075 which has a very large black hole of almost 10 billion solar masses and emits a periodic optical signal that repeats every 542 days.

“The discovery of a compact binary candidate supermassive black hole system like PSO adds to our limited knowledge of the end stages of the merger between supermassive black holes,” added astronomy graduate student Tingting Liu, the paper's first author.

The study was published in the Astrophysical Journal Letters.