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 on 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,” said Neil Gehrels, chief of NASA’s astroparticles physics lab at Goddard Space Flight Center in Greenbelt, Md.
It was bright enough to be seen with the naked eye. But NASA has no reports that any watchers spotted the burst, which lasted less than an hour.
The starburst, which occurred when the universe was about half its current age, 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 about 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 would have vaporized any planet nearby, Gehrels said.
