(ORDO NEWS) — Astronomers have found strong evidence that as a result of collisions between black holes, one of the objects involved in the collision can receive a large enough momentum to leave the galaxy.
This team, led by Vijay Varma, a physicist at the Max Planck Institute for Gravitational Physics, Germany, studied gravitational wave data from a collision event known as GW200129, which was collected using the LIGO and Virgo detectors.
As a result of the analysis, scientists found that the black hole formed during this collision and merger was pushed into space at a speed of 4.8 million kilometers per hour – finds that one of the members of the scientific team described as “amazing and shocking.”
“When two black holes collide, they leave behind a more massive black hole. During this process, the black hole can acquire some speed through the transfer of momentum,” Varma said.
When black holes orbit each other, they emit gravitational waves that carry energy and angular momentum with them. As a result, the orbit is compressed and gradually the black holes approach each other and collide.
However, if black holes have different masses or their own rotation speeds, then this leads to asymmetry of gravitational radiation, and gravitational waves are predominantly emitted in one direction.
Since the basic laws of physics require conservation of momentum, this asymmetry results in a significant amount of “recoil”, causing the resulting black hole to move in the opposite direction.
Such a powerful “bounce” is expected when the orbital plane of a binary system precesses, or “wobbles”. Orbital precession is observed as small changes in the amplitude of the gravitational wave signal.
“This signal also shows strong signs of orbital precession for the first time in the history of binary black holes,” said co-author Scott Field, a mathematician at the University of Massachusetts Dartmouth, USA.
In this work, the researchers showed for the first time that such a collision can lead to the expulsion of a black hole formed as a result of a merger out of the galaxy.
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