WASHINGTON — The explosion of a star halfway across the universe was so huge it set a record for the most distant object that could be seen on Earth by the naked eye.

The aging star, in a previously unknown galaxy, exploded in a gamma ray burst 7.5 billion light years away, its light finally reaching Earth early Wednesday.

The gamma rays were detected by NASA's Swift satellite at 2:12 a.m. "We'd never seen one before so bright and at such a distance," NASA's Neil Gehrels said. It was bright enough to be seen with the naked eye.

However, NASA has no reports that any skywatchers spotted the burst, which lasted less than an hour. Telescopic measurements show that the burst — which occurred when the universe was about half its current age — was bright enough to be seen without a telescope.

"Someone would have had to run out and look at it with a naked eye, but didn't," said Gehrels, chief of NASA's astroparticles physics lab at Goddard Space Flight Center in Greenbelt, Md.

The starburst would have appeared as bright as some of the stars in the handle of the Little Dipper constellation, said Penn State University astronomer David Burrows. How it looked wasn't remarkable, but the distance traveled was.

The 7.5 billion light years away far eclipses the previous naked eye record of 2.5 million light years. One light year is 5.9 trillion miles.

"This is roughly halfway to the edge of the universe," Burrows said.

Before it exploded, the star was about 40 times bigger than our sun. The explosion vaporized any planet nearby, Gehrels said.

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