New Gamma-Ray Burst Record

NASA’s Swift satellite and an international team of astronomers have found a gamma-ray burst from a star that died when the universe was only 630 million years old–less than five percent of its present age. The event, dubbed GRB 090423, is the most distant cosmic explosion ever seen.

NASA’s Swift satellite and an international team of astronomers have found a gamma-ray burst from a star that died when the universe was only 630 million years old–less than five percent of its present age. The event, dubbed GRB 090423, is the most distant cosmic explosion ever seen.

The burst occurred at 3:55 a.m. EDT on April 23rd. Swift quickly pinpointed the explosion, allowing telescopes on Earth to target the burst before its afterglow faded away. Astronomers working in Chile and the Canary Islands independently measured the explosion’s redshift. It was 8.2, smashing the previous record of 6.7 set by an explosion in September 2008. A redshift of 8.2 corresponds to a distance of 13.035 billion light years.

Naked-eye Gamma Ray Burst

A powerful gamma ray burst detected March 19th, 2008 by NASA’s Swift satellite has shattered the record for the most distant object that could be seen with the naked eye.

A powerful gamma ray burst detected March 19th, 2008 by NASA’s Swift satellite has shattered the record for the most distant object that could be seen with the naked eye.Swift’s Burst Alert Telescope picked up the burst at 2:12 a.m. EDT Gamma Ray Burst on March 19, 2008, and pinpointed the coordinates in the constellation Bootes.

Telescopes in space and on the ground quickly moved to observe the afterglow. The burst was named GRB 080319B and registered between 5 and 6 on the visual magnitude scale used by astronomers.the Very Large Telescope in Chile and the Hobby-Eberly Telescope in Texas measured the burst’s redshift at 0.94.

The Mystery of Missing Gamma-ray Bursts

Gamma-ray bursts are by far the brightest and most powerful explosions in the Universe, second only to the Big Bang itself. So it might seem a bit surprising that a group of them has gone missing.

A single gamma-ray burst (GRB) can easily outshine an entire galaxy containing hundreds of billions of stars. Powerful telescopes can see them from clear across the Universe. And because the deeper you look into space, the farther back in time you see, astronomers should be able to see GRBs from the time when the very first stars were forming after the Big Bang.

Farthest GRB
Farthest GRB

Yet they don’t. Gamma-ray bursts from that early epoch seem to be missing, and astronomers are wondering where they are.The answer eventually came from Stan Woosley, a theoretical astrophysicist at the University of California in San Diego. He suggested that when young, supermassive stars with low metal content collapse under their own weight to form black holes, the stars’ rotation funnels the explosive energy into two streamlined jets that shoot out from the stars’ poles, like the axis of a gyro. We only see the burst if one of these two jets happens to be pointed toward Earth. The concentration of energy into narrow jets is why GRBs that we do observe appear so remarkably bright.

The first waves of star formation after the Big Bang should have produced plenty of metal-poor supermassive stars ripe for collapse. If true, GRBs from that epoch should be abundant. So where are they?