Another merger of two intermediate mass black holes has been observed by the LIGO gravitational wave observatories.
There are now three confirmed black hole pair mergers, along with a previously known fourth possible, that lacks sufficient statistical confidence.
These three mergers have all been detected in the past two years and are the only observations ever made of gravitational waves.
They are extremely powerful events. The lastest event is known as GW170104 (gravitational wave discovery of January 4, 2017).
It all happened in the wink of an eye. In a fifth of a second, a black hole of 30 solar masses approximately merged with a black hole of about 20 solar masses. It is estimated that the two orbited around one another six times (!) during that 0.2 seconds of their final existence as independent objects.
The gravitational wave generation was so great that an entire solar mass of gravitational energy was liberated in the form of gravitational waves.
This works out to something like Joules of energy, released in 0.2 seconds, or an average of during that interval. You know, a Tera Tera Tera Terawatt.
Researchers have now discovered a whole new class of black holes with masses ranging from about 10 solar masses (unmerged) to 60 solar masses (merged). If they keep finding these we might have to give serious consideration to intermediate mass black holes as contributors to dark matter. See this prior blog for a discussion of primordial black holes as a possible dark matter contributor: