Now where have we heard THAT news before? For aficionados of NASA’s Swift satellite, or even space science and astronomy in general, this headline probably rings a few bells. Like this one for example, announced on April 28, 2009:
New Gamma-Ray Burst Smashes Cosmic Distance Record
But what many of you may not be aware of is that, within 24 hours of the April 28 headline, Swift detected yet another gamma-ray burst (the death-throes of a massive star), which was even more distant. Why didn’t you know? Well, because we didn’t either!
A Gemini Observatory color image of the afterglow of GRB 090429B, a candidate for the most distant object in the universe. This “izH” image has been constructed from three images taken at the Gemini Observatory North telescope through different optical and infrared filters. The red color results from the absence of all optical light, which has been absorbed by hydrogen gas in the distant universe. Without that absorption, the afterglow color would be bluer than any of the galaxies and stars seen here. (Credit: Credit: Gemini Observatory/AURA/NASA/ Levan, Tanvir, Cucchiara, Fox)
The explosion, termed GRB 090429B, was detected on April 29, 2009, by Swift. Nino Cucchiara and his then-PhD supervisor Derek Fox, along with collaborators including Nial Tanvir and Andrew Levan from the UK, observed the GRB with the 8-meter Gemini telescope in Hawai’i, and found that it was red. Very red.
Now this can mean two things: either it’s a really long way away, or it went off in a really dusty galaxy. So Nino and collaborators asked the Gemini operators to take a spectrum of the source, which would provide a measurement of the object’s distance.
Unfortunately, even on Hawai’i, astronomers are at the mercy of the weather. And just as Gemini prepared to take the spectrum, the weather turned and observing was impossible. By the next observing opportunity, the GRB was too faint to take a usable spectrum.
Fortunately, that’s not the end of the story, but it made the job much harder. Now, after two years of hard graft, and observations with Gemini and with the Hubble Space Telescope, Nino and collaborators have released their findings. And the cosmic record holder has fallen!
Well, probably. Their result shows, based on analysis of the images, that there is a 99.3 percent likelihood that this object was more distant that GRB 090423 — the object being trumpeted just before this star exploded. The precise distance is not known because of the lack of spectrum, but there is a 98.9 percent chance that is lies further away than a galaxy discovered in 2010 — 13.07 billion light years away — which surpassed April 2009’s GRB 090423 as the most distant known object. Whether it is the farthest object ever seen is not entirely clear: a galaxy detected in 2011 may lie a little further away…. or may actually not be a distant object at all.
Either way, this new result is another triumph for GRB science, for Swift and the optical and infrared facilities like Gemini, and above all for the hard-working determination of the scientists studying these enigmatic phenomena.
Follow Phil Evans on twitter: @swift_phil
OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.