Press Release

HAWAII TELESCOPES CATCH MOST DISTANT EXPLOSION

September 12, 2005

Subaru succeeded in obtaining a precise distance to the most distant cosmic explosion ever seen. Such cosmic explosions, called gamma-ray bursts, are thought to occur when a massive star collapses and creates a black hole. Observations by Subaru and other telescopes on Mauna Kea, Hawaii, were instrumental in showing that this explosion is 500 million light-years more distant than all previously known explosions of its kind. The distance of the explosion, 12.8 billion light-years away, is at the observational frontier of space.


Astronomers from Japan and the University of Hawaii Institute for Astronomy have used telescopes at the Mauna Kea and Haleakala observatories to measure the distance to the farthest cosmic explosion ever seen, opening a new view into the frontiers of space.

The explosion, known to astronomers as a "gamma-ray burst," was first detected by NASA's Swift Gamma-Ray Burst satellite on the morning of September 4th, before being pinpointed by telescopes in Chile. Telescopes around the world rushed to catch a glimpse of the fading explosion, including the Subaru telescope and NASA's Infrared Telescope Facility (IRTF) on Mauna Kea, and the MAGNUM telescope on Haleakala.

Nobuyaki Kawai from the Tokyo Institute of Technology led a team that used the 8.2-meter Subaru telescope to measure a precise distance to the explosion: 12.8 billion light-years. This is the most distant explosion astronomers have ever seen. There are less than fifty other known objects at such a great distance from Earth, and the farthest is only a mere 50 million light-years (or 0.4%) more distant. Most of these are too faint for all but the largest of telescopes, so astronomers are excited by the relatively bright explosion.

"This explosion occurred at the edge of the known Universe," Kawai enthused. "One day soon, gamma-ray bursts will let us see further than ever before."

The remnants of such explosions fade away in a matter of days, so cosmic explorers must be on their toes to catch them, UH astronomer Paul Price explained. When his cell phone rang at 2 a.m. on September 4, Price was ready to take charge of pointing IRTF and MAGNUM to the site of the explosion.

MAGNUM has a novel camera capable of taking visible and infrared images simultaneously, allowing Price, UH astronomer Lennox Cowie and University of Tokyo astronomers Yuzuru Yoshii and Takeo Minezaki to estimate the distance to the explosion from its color, reddened by the expansion of the Universe.

"It was immediately apparent from the images that we were looking at a source at the frontier of space," Cowie said. "It's so much more distant than all the other gamma-ray bursts we've seen up until now."

This discovery comes less than a decade after scientists first learned that the explosions were coming from beyond our own galaxy. It wasn't even until three years ago that astronomers pieced together the puzzle of what causes these tremendous explosions.

According to Price, gamma-ray bursts are the death shrieks of a massive star, and where there are dying stars, there must be living ones as well. "Because these explosions are so bright, they give us the opportunity to study stellar birth and death in the most distant Universe in a manner we could only dream about a couple of years ago."

Normally, astronomers study the early Universe through the light of distant galaxies, or that generated by black holes steadily devouring matter. But the remnants of the gamma-ray bursts outshine even the most hungry of galactic black holes, allowing them to be seen across the Universe. Gamma-ray burst researchers around the world are hoping that this success is a taste of things to come, and that they will have further opportunities to push back the frontier.

The Subaru telescope, Japan's largest optical-infrared telescope, is operated by the National Astronomical Observatory of Japan (NAOJ). The MAGNUM telescope, run by the University of Tokyo, is a 2-meter telescope on Haleakala dedicated to observing galaxies harboring black holes. The 3.5-meter Infrared Telescope Facility is operated for NASA by the UH Institute for Astronomy.

Subaru's Gamma-ray burst team consists of researchers from the Tokyo Institute of Technology, NAOJ, and Aoyama Gakuin University. Kyoto University, RIKEN, the University of Tokyo, Hiroshima University, and the University of California Berkeley.

The Institute for Astronomy at the University of Hawaii conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the
observatories on Haleakala and Mauna Kea.

Pictures and further information on this release are available at:

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Subaru FOCAS (Faint Object Camera and Spectrograph) images of the afterglow of the gamma-ray burst GRB 050904 in two different filters (8000 angstrom Ic and 9000 angstrom Z' band). The different appearance hints at the great distance of the object.
Schematic diagram of the Subaru Telescope/FOCAS spectrum of the afterglow. The black line shows the intensity of the gamma-ray burst afterglow at different wavelengths. The blue line is the transmission curve of light in the Ic-band, the red line is that of Z'-band. Absorption of light by hydrogen and other elements in the foreground cause the steep drop off of the spectrum at shorter wavelengths. The spectrum shows the precise wavelength of the cutoff, revealing a precise distance to the object.

 

 

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