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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:
Related information is available at:
 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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September 12, 2005 |
