ASTRONOMERS HAVE shed a bit of light on the cosmic “Dark Ages”. They have discovered the most distant star yet found, one so far away that it took its light more than 13 billion years to reach us.
These dark ages were a time before light when no stars brightened the universe. It was a time not too terribly long after the Big Bang, when matter in the universe was just too hot to clump together to form stars.
Astronomers from the UK and Italy announced this record-setter this morning in the journal Nature, which publishes two reports on the object. The star’s light first appeared last April when an incoming wave of gamma rays smacked into the earth.
Nasa’s orbiting satellite Swift gave early warning to the world that a giant star had exploded in what is known as a gamma-ray burst.
These are the largest explosions seen in the cosmos, so large that when they go off the light emitted is brighter than all the stars of the universe put together.
Astronomers are hugely interested in these events and Swift is there to tell ground-based observers where to point their telescopes to capture the fading afterglow as the star’s dying light fades.
This tells them how far away the burst was, but there was surprise when it emerged that this explosion was from the most distant object yet discovered, making it one of the oldest stars ever seen.
The inelegantly named GRB 090423 died just 640 million years after the Big Bang and a full nine billion years before our own sun formed to light our way. It moved us a bit further back in time and a bit further away, beating the previous most distant object by 180 million light-years.
Gamma-ray bursts occur when a large star collapses to form a black hole, stated University College Dublin’s Dr Brian McBreen.
We only have “theoretical guidance” about just how far back in time we can go towards the Big Bang, but every discovery of this kind is important, he said. “It is telling us there were stars 640 million years after the Big Bang. It is quite exciting.”
It means the Dark Ages of the cosmos didn’t last quite as long as previously thought, but Dr McBreen expects that we will keep having to push back the clocks.
“The significance of this is: if there is one then there are many. You can expect more of these. It is only a matter of time and of facilities.”