Astronomers detect signs of possible black hole merger

Hyperaxion Jun 25, 2020

The event would be linked to the flare of light observed in a quasar – a supermassive black hole that glows brightly while devouring the matter around it.

On May 21, 2019, gravitational wave detectors LIGO in the United States and Virgo in Italy picked up signs of a possible merger of two black holes. The hypothesis, which has yet to be confirmed, came after a flare of light was observed in a quasar, according to a group of astronomers led by the California Institute of Technology (Caltech).

Astronomers detect signs of possible black hole merger
An artist’s impression of the two black holes in the quasar disk. (Credit: Caltech / R. Hurt).

Based on this association, the scientists published a study on Thursday (25) in the Physical Review Letters. According to them, the merger took place inside the disk of gas around a quasar. As the scientists explain, if two stellar-mass black holes merge inside that disk, they can stir up the gas and make the quasar shine even brighter.

To test this hypothesis, the team examined data from the Zwicky Transient Facility (ZTF) catalog, which stores information about cosmic events, particularly those with varying luminosities. Comparing the data with those detected by the LIGO-Virgo observatories in 2019, scientists discovered the flare of light coming from a quasar in the same region of the sky, but 35 days later.

Quasars are known to vary in brightness, but the researchers showed that the observed light was inconsistent with what is normally seen in that particular region of space. They also ruled out other possible explanations, such as the explosion of a supernova.

In the article, astronomers argue that the intense light was the result of a collision between two black holes on the quasar disk. According to the model, the high-speed collision resulted in another black hole, creating a shock that heated the gas, caused the flare and, consequently, the detected gravitational waves. The 35-day “delay” is the result of light scattering across the quasar opaque disk.

Quasar disks concentrate many black holes, and the researchers predict that the black hole resulting from the collision will orbit the central supermassive black hole of the quasar and will again collide with another black hole approximately one and a half years after the initial merger – resulting in another flare.

Therefore, scientists plan to continue observing this turbulent region of space for years to come. “The result suggests an exciting program of future observations [of quasars] that follow up on gravitational-wave candidates,” said Patrick Brady, a LIGO-Virgo spokesman, in a statement.

Related topics:

black hole LIGO-Virgo Quasar


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