A 'bang' in LIGO and Virgo detectors signals most massive gravitational-wave source yet

For all its vast emptiness, the universe is humming with activity in the form of gravitational waves. Produced by extreme astrophysical phenomena, these reverberations ripple forth and shake the fabric of space-time, like the clang of a cosmic bell.

Now researchers have detected a signal from what may be the most massive black hole merger yet observed in gravitational waves. The product of the merger is the first clear detection of an "intermediate-mass" black hole, with a mass between 100 and 1,000 times that of the sun.

The signal, resembling about four short wiggles, is extremely brief in duration, lasting less than one-tenth of a second. From what the researchers can tell, GW190521 was generated by a source that is roughly 5 gigaparsecs away, when the universe was about half its age, making it one of the most distant gravitational-wave sources detected so far.

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Credit: LIGO/Caltech/MIT/R. Hurt (IPAC)

This artist's concept illustrates a hierarchical scheme for merging black holes. LIGO and Virgo recently observed a black hole merger with a final mass of 142 times that of the sun, making it the largest of its kind observed in gravitational waves to date. The event is thought to have occurred when two black holes of about 65 and 85 solar masses spiraled into each other and coalesced.

Theoretical models indicate that nature is not likely to form black holes of this heft; in particular models identify a range of masses between 65 and 130 solar masses, called the "pair instability mass gap," in which it is thought that black holes cannot be formed by a collapsing star.

So how did the two merging black holes observed by LIGO and Virgo originate? Scientists think that these black holes may have themselves formed from the earlier mergers of two smaller black holes, as indicated in the illustration.

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On 26th of December 2015 the LIGO detectors picked up a second gravitational-wave signal, dubbed "GW151226", from yet another pair of merging black holes.

On Aug. 17, 2017, the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo detected, for the first time, gravitational waves from the collision of two neutron stars.

The event was not only “heard” in gravitational waves but also seen in light by dozens of telescopes on the ground and in space.