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On September 14, 2015, scientists
in the LIGO Scientific Collaboration,
directly observed, for the first
time, the existence of
gravitational waves. And not
only that, they were also able
to determine that the source of
these waves is the product of a
collision between two massive
black holes 1.3 billion light
years away - a remarkably extreme
event that, until now, had not
been observed.
Now, for the second time, scientists
have detected gravitational waves
this time, emanating from
slightly farther out in the
universe, at 1.4 billion light
years away. On December 26, 2015,
LIGO detectors picked up a faint
signal, which scientists have now
determined to be gravitational
waves produced by the collision
of a second pair of black holes.
The black holes orbited each
other at half the speed of light
before merging in a collision
that produced as much energy as
our sun, in the form of
gravitational waves. These black
holes were less massive than
the first pair, and produced a
much subtler signal, that LIGO
scientists were nonetheless able
to detect, using advanced data
analysis techniques.
The scientists converted the
gravitational wave signal into
sound, and compared the resulting
audio with that of the first
gravitational wave signal.
That signal produced a clear and
sharp "chirp" that scientists
could clearly see in the data.
The second signal
was subtler, producing a more
muted, and slightly longer chirp.
This new detection once again
confirms Einstein's theory of
general relativity, and also
proves LIGO's potential for
detecting extremely faint
gravitational waves, traveling
from the farthest reaches of space.