Astronomers are said to be 'in shock' after the brightest display of gamma rays ever seen occurred just as the world's telescopes turned to watch.
The BBC reports that Markarian 421 - an active galaxy about 397 million light-years away, where super-massive black holes spew massive amounts of radiation, particles and light into space - flared up at exactly the right moment.
Astronomers have been blown away by the coincidence, and the opportunity it gives researchers to examine how the blazar works.
The programme to study the galaxy in many different bands of light began only recently, with many of the world's top observatories joining in, such as the Fermi gamma-ray telescope.
But Markarian 421, which is located in the constellation of Ursa Major, hadn't flared up since 1996, and astronomers were not aware that it was about to burst into life just as a programme to study it began.
"I'm in shock and awe at how bright it is," said Julie McEnery, project scientist for the Fermi. "This thing is blowing us away."
On astronomy forums around the web observers expressed their delight.
"Dozens of telescopes have caught the event, across all frequencies. Should result in some good data!" said a user at Stargazer's Lounge.
A meeting at the American Physical Society in Denver is also currently underway, and Markarian 421 is said to be the talk of the town.
"We never know when exactly it's going to get very bright and this time it was kind enough to do just that when we had a very large number of telescopes trained on it," Prof Madejski - a co-investigator on the NuStar X-ray telescope, told the BBC.