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THE search for gravitational waves is back on, and this time we are expecting a deluge.

The Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US made a huge splash in 2016, when it announced the detection of faint ripples in space-time produced by the collision of a pair of black holes. It has since spotted 10 more gravitational-wave events. Now, following upgrades, LIGO should see one a week when it starts up again on 1 April.

“We’re making the transition from having a slow drip of events to opening the faucet,” says Luis Lehner at the Perimeter Institute for Theoretical Physics in Waterloo, Canada. “It’s going to be amazing.” Astrophysicists are hoping this torrent will give us answers to these five questions:

How do black holes pair up?

We still don’t know what brings black holes together. Either the stars that collapse to create them start out in a pair – a binary system – or mature black holes are somehow pushed together by interactions with other objects. Or maybe both. One way to find out is to see whether the spins of merging behemoths are aligned.

What is inside a neutron star?

Neutron stars are the city-sized remnants of massive stars, squeezed to densities greater than that inside the nucleus of an atom. We have felt the ripples from collisions between them once. More detections will let us better probe their innards.

Can we see inside a supernova?

Core-collapse supernovae are the universe’s most spectacular fireworks display – dramatic explosions of dying giant stars that give birth to neutron stars and black holes. So far, we know them only from the light they emit, but they should produce gravitational waves too. Glimpsing these waves should let us peer inside.

Do black holes have a wall of fire?

In 2016, a team led by Niayesh Afshordi at the Perimeter Institute claimed that the first gravitational wave ever detected was echoing. That was a big surprise, because it would indicate the presence of a ring of high-energy particles around a black hole, known as a firewall. This would contradict Einstein’s theory of general relativity. LIGO’s third run should settle the matter.

Are black holes even real?

A black hole’s whole shtick is that you can’t see it. The only ways we know they are out there are that we see gas, dust and stars falling in, and we can detect gravitational waves from them.

Then again, it is possible that at least some of the things we think are black holes are in fact exotic, hypothetical objects called boson stars. Their strange form prevents them collapsing to become a black hole, but they would distort space-time in much the same way. The only way to find out if boson stars are real is to search gravitational wave signals for a distinct frequency.