Explosion 7.5 billion light-years away could be seen by naked eye
Saturday, March 22, 2008
(03-22) 04:00 PDT 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.
NASA has no reports that any sky-watchers 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.
The starburst would have appeared as bright as some of the stars in the handle of the Little Dipper constellation, said Pennsylvania 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 the sun.
The explosion vaporized any planet nearby, said Gehrels, chief of NASA's astroparticles physics lab at Goddard Space Flight Center in Greenbelt, Md.