[ExI] LIGO found a second Black Hole collision!

[John Clark]

After analyzing the data from LIGO's brief engineering run the scientists
there just announced they have found a second Black Hole merger. A Black
Hole of 14 solar masses merged with one of 8 solar masses and produced a
Black Hole of 21 solar masses and gravitational waves with 1 solar mass of
energy. It happened 1.4 billion light years away, about the same distance
as the first merger that was announced a few months ago, but the signal was
weaker because the Black Holes involved were smaller (14 and 8 vs 36 and
29) and also because the orbit of the Black Holes was more edge on relative
to the Earth. Edge on means the signal is weaker but it also means it's
easier to determine the spin, so unlike the first detection this time we
can say with certainty that at least one of the Black Holes was spinning.
And although weaker the signal lasted longer, almost a full second versus a
fifth of a second the first time because being smaller the holes generated
waves with higher frequencies that LIGO is more sensitive to.

And they're looking at at least one other suspected merger but they're only
85% certain it's real and that's not good enough to claim discovery, but
there may be others so there may be a third announcement before long. Not
bad for observing for only 18 days. The instrument was running at only one
third power but that was still good enough to determine that 2 mirrors 4
kilometers apart had changed their distance by less than a billionth of a
nanometer. I can't wait for September when the 2 LIGOs get back online and
are joined by a third detector, VIRGO in Italy. Spike's right, this is a
great time to be alive!

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.241103

 John K Clark
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