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Subaru Telescope Detects the Most Distant Galaxy Yet
and Expects Many More

March 19, 2003

Part 2 of 2

The SDF team expects to find many more distant galaxies through
continued observations. Before the first stars and galaxies formed,
the universe was in a stage that Astronomers call "the dark ages of
the universe". Determining when the dark ages ended is one of the
most important astronomical questions of our time. Core members of
the team, Keiichi Kodaira from the Graduate University of Advanced
Studies in Japan, Nobunari Kashikawa from the National Astronomical
Observatory of Japan, and Yoshiaki Taniguchi from Tohoku University
hope that by detecting a statistically significant number of distant
galaxies, they can begin to characterize the galaxies that heralded
the end of the universe's dark ages.

Note 1: The more distant a galaxy is from us, the faster it is moving
away from us. As a result, light from distant galaxies are doppler
shifted to longer, or redder wavelengths. This phenomenon, called
redshift, is a direct consequence of the expansion of the universe.
The best real life example of a doppler shift is the change in pitch
of the siren from an emergency vehicle as it passes by. As an
ambulance approaches its siren has a high pitch, or a sound of
shorter wavelength. As it moves away, the siren has a lower pitch or
a sound of a longer wavelength. Astronomers use the ratio between the
shift in wavelength and the original wavelength of the light from a
galaxy to indicate its distance, and this number is also called
redshift. What distance a redshift corresponds to depends on the
overall structure of the universe. The distances quoted in this press
release are based on recent research indicating that the universe is
13.7 billion years old.

Note 2: The speed of light is approximately 300,000 kilometers per
second, the speed required to circle the Earth seven and a half times
in a second. Light travels 10 trillion kilometers, or one light year,
in a year

Note 3: Following the Big Bang, when the universe came into
existence, the universe was a hot plasma where elementary particles
whizzed about independently. The universe cooled as it expanded, and
about one million years after the Big Bang, the universe was cool
enough for protons and electrons to combine and form neutral hydrogen
atoms. This epoch is called the"dark ages" of the universe.
Astronomers think that when the first stars and galaxies formed,
their light ionized the neutral hydrogen, and returned the universe
to a plasma. When the first stars formed and the dark ages of the
universe ended is one of the most important astronomical questions of
our time. 

Professional References

The information in this press release is based on a research article
to appear in the April 2003 issue of the Publications of the
Astronomical Society of Japan (PASJ Vol. 55, No. 2). 

Contacts
Keiichi Kodaira
The Graduate University for Advanced Studies
Japan
Phone: +81-46-858-1512
email: kodaira_keiichi{at}soken.ac.jp

Nobunari Kashikawa
National Astronomical Observatory of Japan
Japan
Phone: +81-422-34-3512
email: kashik{at}zone.mtk.nao.ac.jp

Yoshiaki Taniguchi
Tohoku University
Japon
Phone: +81-22-217-6508
email: tani{at}terra.astr.tohoku.ac.jp

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