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After nine months of searching the skies, scientists were preparing to pack up their equipment when they found something that set their world - and universe - alight.
The Australian National University team, working with others around the world, has seen for the very first time two neutron stars colliding - and it has them extremely excited.
The discovery has the potential to revolutionise our understanding of the universe and how elements are formed.
The ANU's Susan Scott, chief investigator with the Centre of Excellence for Gravitational Wave Discovery (OzGrav), says astronomers have been waiting for decades to see neutron stars colliding, but until now had to rely on more or less pointing their telescopes at the sky at random.
Her gravitational wave detectors - which look for the faint ripples in the universe theorised by Einstein but not observed until 2015 - "just sit there and wait for something to come in".
"We were very, very blessed because eight days before we concluded that nine-month observing run, we got this signal and it was the two neutron stars," Professor Scott told AAP.
Once Prof Scott's team knew the patch of sky the waves were coming from, they sent an alert out to astronomy projects around the world - including ANU's own SkyMapper telescope.
"That was unprecedented too because we had just about every astronomy project around the world scrambling to re-point their telescopes and satellites, to try to find the actual source in that bit of sky," she said.
"We've never seen an effort like this in science."
That alert came through to ANU astronomer Christian Wolf's phone in the middle of the night and he missed it - until woken by a junior team member banging on his front door at 2am.
"We were totally caught by surprise. We had written this off, we thought that's it, come back next year and try again - and then it happened," Dr Wolf said.
The discovery makes it much more likely more neutron star collisions will be found in the future, giving scientists more chances to learn about the stars and how they create rare earths and precious metals.
"It's not related to the Big Bang as such, but it is a little bang if you want, a bang that is crucial for making rare elements," Dr Wolf said.
The equipment used to find the gravitational waves has since been shut down to be upgraded and made even more sensitive.
Prof Scott hopes when it comes back online next year the team will be able to discover gravitational waves from supernovas, cosmic streams and eventually look back to the beginning of the universe.