Ancient light as seen by Gemini (false colour)
By Hamish Johnston
One problem with reporting breakthroughs in astronomy is that someone is always claiming to have discovered the oldest/largest/brightest/dimmest/smallest object yet. And by the time you have written your story — someone else will claim to have done better.
That’s why my eyes rolled a bit when I read the press release “Farthest known object: New gamma-ray burst smashes cosmic distance record”, which arrived last night from the AAS.
However, upon closer inspection, this one really does look interesting.
As its name suggests, GRB 090423 was discovered last Thursday and astronomers believe that the burst occurred more than 13 billion years ago — about 630 million years after the Big Bang.
That’s about 100 million years older than the previous record, which was held by a ancient galaxy.
Gamma rays from GRB 090423 were first spotted by NASA’s Swift satellite, which quickly turned its X-ray and ultraviolet instruments on the object. No visible light was seen, but Swift did manage to capture the burst’s fading X-ray afterglow.
Meanwhile here on Earth, astronomers were turning their telescopes to that patch in the sky. The Gemini North and UK Infrared telescopes in Hawaii managed to capture infrared light from the burst (above).
By analysing how much the wavelength of the light light has been red-shifted, astronomers worked out that the light has travelled over 13 billion light years before reaching Earth.
The chart below shows the age of GRB 090423 compared to other known objects.
You can read all about the search for gamma ray bursts in this article in Physics World.
Beyond redshift eight