When the first black hole collision was detected in 2015, it was a watershed moment in the history of astronomy. With gravitational waves, astronomers were observing the universe in an entirely new way. But this first event didn’t revolutionize our understanding of black holes — nor could it. This collision would be the first of many, astronomers knew, and only with that bounty would answers come.

“The first discovery was the thrill of our lives,” said Vicky Kalogera, an astrophysicist at Northwestern University and part of the Laser Interferometer Gravitational-Wave Observatory (LIGO) collaboration that made the 2015 detection. “But you cannot do astrophysics with one source.”

Now, gravitational wave physicists like Kalogera say they are entering a new era of black hole astronomy, driven by a rapid increase in the number of black holes they are observing.

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The latest catalog of these so-called black hole binary mergers — the result of two black holes spiraling inward toward each other and colliding — has quadrupled the black hole merger data available to study. There are now almost 50 mergers for astrophysicists to scrutinize, with dozens more expected in the next few months and hundreds more in the coming years.

Read more: Quanta