Back in February, scientists announced they had finally detected gravitational waves at the Laser Interferometer Gravitational Wave Observatory, known as LIGO. Today, June 15, they announced a second detection of gravitational waves. Just like the first signal, this one came from a pair of merging black holes.
The discovery was announced at the 228th meeting of the American Astronomical Society in San Diego, California.
Gravitational waves are ripples through space-time that happen when something like a star collapses or two black holes merge. Einstein predicted their existence 100 years ago, but all searches had come up empty-handed until the signal detected in February.
How LIGO found them: The black holes that produced this second signal were about 1.4 billion light-years away. One was about eight times the mass of the sun and the other was about 14 times the mass of the sun, according to LIGO spokesperson Gabriela González.
The black holes circled each other before finally colliding at half the speed of light. The cataclysmic merger produced a huge burst of energy, equivalent to the mass of our sun, that spread through space as gravitational waves.
LIGO picked up the gravitational waves by detecting small distortions in its twin laser beams. You can actually hear "chirps" from the signal:
Why it matters: After the first detection in February, it was possible that physicists just got really lucky. A second detection is huge; it opens the door for much more research. Gravitational waves are all around us, and we'll likely see many more signals.
"We can tell you now, the era of gravitational wave science has begun," Gonzalez said during the press conference.
The more gravitational waves we detect, the better we'll be able to test Einstein's theory of general relativity, and it could reveal more about black holes.
The research describing the second signal is published in the Physical Review Letters.