The twin detectors of the Laser Interferometer Gravitational-wave Observatory has detected its second confirmed gravitational wave signal. Like the first, historic discovery of gravitational waves in September, this signal was also caused by a black hole merger, only this time the black holes are much smaller, "weighing in" at 8 and 14 solar masses. The discovery not only reinforces Einstein's general relativity, but it gives us an enticing clue to how many black holes there are in the universe and opens up a new era of gravitational astronomy.
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