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This pair of visible-light and near-infrared Hubble Space Telescope photos shows the giant star N6946-BH1 before and after in vanished out of sight by imploding to form a black hole. The left image shows the 25 solar mass star as it looked in 2007. In 2009, the star shot up in brightness to become over 1 million times more luminous than our sun for several months. But then it seemed to vanish, as seen in the right panel image from 2015. A small amount of infrared light has been detected from where the star used to be. This radiation probably comes from debris falling onto a black hole. The black hole is located 22 million light-years away in the spiral galaxy NGC 6946. Photo: NASA, ESA, and C. Kochanek (OSU)

In a galaxy 22 million light-years distant, a black hole was born. For the first time in recorded history, humans were watching the astronomical phenomenon, reports a team from NASA, Ohio State, and Caltech.

The “Fireworks Galaxy” is known for its frequent supernovae. But starting in 2009, one of its stars named N6946-BH1 brightened just a bit – but then had disappeared from the most advanced telescopes by 2015.

The team used the Hubble and Spitzer space telescopes, the Large Binocular Telescope, and a variety of other methods to try and get a glimpse of the vanished star, as they describe in the Monthly Notices of the Royal Astronomical Society. But there wasn’t even any infrared radiation that marked the spot where the star had been, proving it wasn’t hidden behind a dust cloud or blocked by another object out in space, they said.

By process of elimination, they have determined that the star is just no longer there. Although it was 25 times more massive than our sun, it didn’t explode – instead it fizzled out, and left a blank spot where it had once been fixed in our sky, the team reports.

“N6946-BBH1 is the only likely failed supernova that we found in the first seven years of our survey,” said Scott Adams, a former Ohio State student now at Caltech.

The team monitored galaxies for years, looking for evidence of other supernovae and black holes.

“During this period, six normal supernovae have occurred within the galaxies we’ve been monitoring, suggesting that 10 to 30 percent of massive stars die as failed supernovae,” explained Adams.

Their conclusions could turn some traditionally accepted astrophysics, added Christopher Kochanek, a professor of astronomy at Ohio State.

“They typical view is that a star can form a black hole only after it goes supernova,” he said. “If a star can fall short of a supernova and still make a black hole, that would help to explain why we don’t see supernovae from the most massive stars.”

"In fact, not having a supernova means it may be easier to form a black hole,” said Krzystof Stanek, also of Ohio State.

“I suspect it’s much easier to make a very massive black hole if there is no supernova,” said Stanek.

Black holes are only beginning to be analyzed by science, a full century after Albert Einstein’s theories of relativity. The detection of gravitational waves, the ripples in space-time created by the collision of two black holes, was first announced last year by the Laser Interferometer Gravitational-Wave Observatory.

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