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 
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:
https://darkmatterdarkenergy.com/2016/06/17/primordial-black-holes-as-dark-matter/
Image credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)
Dark Matter, Dark Energy, Dark Gravity 
June 6th, 2017 at 4:51 am
Is there a way to harness this energy? By my logic, if this energy were able to be harnessed and used, it could solve the problem of energy for space travel if the process were able to used on a small enough scale to fit in a space vehicle. This could not only help to explore further into Space, but allow us to colonize planets further from Earth than what we could currently reach. It seems there is so much energy available in the Universe yet we have yet to explore ways to harness the varying forms of energy other than the most mundane that we currently use on Earth. Thanks.
June 6th, 2017 at 8:27 am
It is extremely weak by the time it reaches our galaxy. And remember the high energy output only lasts for a fraction of a second. We have to expend a large amount of energy just to detect this very weak signal. The only practical way to harness gravitational energy in aufficient degree would be a near flyby for the gravitational slingshot effect such as is done with planetary approaches in our solar system. And we would want it not to be a colliding binary system.
June 7th, 2017 at 12:45 am
Thank-you for your response. It’s somewhat baffling and frustrating that with all the energy in the Universe that we can’t find a renewable source of efficient high output energy that would allow us to travel at speeds where we can make manned deep space voyages and return within our own life-spans.
I watched a Ted talk about a company that is supposedly creating a device that will create antimatter and will use it to propel a space ship at 1g, but it seemed very far fetched considering it would be a monumental breakthrough that even CERN has been unable to do.
Regards.
December 7th, 2017 at 9:03 pm
[…] LIGO has recently detected several merging black holes in the tens of solar mass range. However the frequency of LIGO detections appears too low by two orders of magnitude to explain the amount of gravitationally detected dark matter. PBHs in this mass range are also constrained by cosmic microwave background observations. […]