Mauna Kea telescopes play key role in distant discovery

LONDON >> Hawaii telescopes have spotted what may be the most distant object ever observed in the universe — a pulse of high energy radiation sent by a disintegrating star near the edge of the observable universe.

The stellar blast was first spotted by a NASA satellite in April 2009, but researchers announced Wednesday that they have since gathered data placing it more than 13 billion light years away — meaning that the event took place when the universe was still in its infancy.

Andrew Levan, one of the scientists behind the discovery, said this blast from the past blew open a window onto the universe’s early years, showing that massive stars were already dying within the first few hundred million years of the birth of the universe.

This particular explosion wasn’t a supernova but a gamma ray burst, the name given to a short but powerful pulse of high energy radiation. Such bursts, thought to result from the collapse of massive stars into black holes, shoot jets of energy across the universe.

“There are some uncertainties,” said Antonio Cucchaiara, the lead author of the study. “However if I were in Vegas, I would never bet against the odds that this is the most distant (gamma ray burse) ever seen and we estimate that there is even a 23 percent chance that it is the most distant object ever observed in the universe.”

NASA’s Neil Gehrels, who serves as the lead scientist on Swift, the gamma-ray detecting satellite which first picked the distant burst’s signal, said that “we only see about one in 1,000 of all the gamma ray bursts that go off.”

Not only are gamma ray bursts more powerful than supernovae, they’re faster too — typically lasting only a few seconds or minutes. They work differently as well. Whereas a supernova spreads its radiation all around, gamma ray bursts shoot it out in narrow beams, like a laser, which can make them hard to detect.

So when a promising one comes along, scientists take note.

Levan said he was at an early-morning meeting in Sweden on April 29, 2009, when his phone went off, alerting him to the explosion. From that moment on, it was a race against time. Gamma ray bursts come and go far too quickly for telescopes, but their afterglows linger for a little while longer and can be analyzed by astronomers.

Levan rushed out of the meeting.

“Fortunately the office was next door,” he said. “So I was able to rush into the building and get online.”

There Levan got a little less lucky. Some of the world’s most powerful telescopes were soon tasked with tracking the burst, but the view from Chile’s La Silla Observatory was hampered by unfavorable atmospheric conditions, while two Hawaiian telescopes — Gemini North and the United Kingdom Infrared Telescope — were buffeted by high winds. Chile’s Very Large Telescope managed to train its eye on the sky for a while, but by then it was already getting light.

But the telescopes did gather some data and a team of astronomers spent the next two years painstakingly trying to build context and double-check their observations. Their paper, due to published soon in Astrophysical Journal, stated with 90 percent certainty that the gamma ray burst had been spotted between 13.11 billion and 13.16 billion light years away, surprisingly close to the advent of the Big Bang about 13.7 billion years ago.

Images from the Gemni telescope on Mauna Kea show what astronomers say is the infrared afterglow from the gamma ray burst.

“Gemini was the right telescope, in the right place, at the right time,” said Cucchiara. “The data from Gemini was instrumental in allowing us to reach the conclusion that the object is likely the most distant GRB ever seen.”

Cucchiara said the team was able to take data from Gemini and combine it with wider-field images from the United Kingdom Infrared Telescope, also on Mauna Kea, to estimate the gamma ray burst with a high degree of confidence.

Gehrels, whose satellite identified the burst but who wasn’t involved in drawing up the paper, said he believed Levan was right — praising his team’s “careful analysis.”

But other outside experts said they were skeptical. Richard Ellis, a professor of astronomy at the California Institute of Technology, called the discovery “potentially very exciting” but said that there wasn’t enough data to justify such a bullish estimate. In any case, he warned of the difficulties associated with peering across such a vast distance.

Richard McMahon, a professor of astronomy at Cambridge University, made a similar point, pointing out that the mechanics of how gamma ray bursts occurred were still too little understood to rule out the possibility that some other factor could be at play. “There are still some surprises in store for us,” he predicted.

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Online:

NASA Swift Homepage: http://heasarc.nasa.gov/docs/swift/swiftsc.html

Gemini North Telescope: http://www.gemini.edu/

United Kingdom Infrared Telescope: http://www.jach.hawaii.edu/UKIRT/