Oldest and most distant galaxy ever discovered was a prolific star factory
Astronomers have spotted the most
distant galaxy ever seen after a faint
ray of light struck a telescope on a
volcano in the middle of the Pacific.
The ancient group of stars lies 30bn
light years from Earth, far beyond
the handle of the Big Dipper that
traces a celestial saucepan in the
constellation of Ursa Major.
Researchers detected the galaxy with
a new infrared instrument that was
fitted last year to the Keck telescope
that sits on the summit of Mauna Kea,
a dormant volcano in Hawaii.
Analysis of light coming from the
galaxy showed that it formed only
700m years after the big bang, or
13.1bn years ago, making it the
oldest and most distant galaxy
known.
"This is really a quest to understand
our origins," said Steve Finkelstein ,
an astronomer at the University of
Texas at Austin. "By trying to push
further and further back in time, we
are really studying the origins of our
own Milky Way galaxy."
Because the universe is expanding,
light from stars and other celestial
objects is stretched out as it travels
through space. This increases its
wavelength. The effect is called
redshift because it makes visible light
look redder.
Finkelstein used the Mosfire (Multi-
Object Spectrometer for Infra-red
Exploration) instrument on the Keck
telescope to survey 43 distant galaxies
that had been glimpsed by the Hubble
Space Telescope but never confirmed.
The device picked up light from only
one, a galaxy that goes by the
cumbersome name of z8_GND_5296,
according to a report in the journal
Nature.
The light coming from the galaxy was
more redshifted than astronomers
had seen before, making it 40m years
older than the previous record
holder. The colour of the galaxy
suggested it was rich in metals.
Early measurements showed that the
galaxy had a mass of 1bn suns, which
is 40 to 50 times lighter than the
Milky Way. What surprised
astronomers most was the intense
rate the galaxy was churning out
stars, around 150 times faster than
the Milky Way.
"We didn't think you could make
galaxies with such intense star
formation rates in the early universe.
Star formation tends to be
proportional to the mass of a galaxy,
and the masses of galaxies in the
early universe tend to be small," said
Finkelstein.
The scientists have a couple of
potential explanations for the
galaxy's extraordinary rate of star
creation. It may contain more gas
than expected, which is used in the
manufacture of stars. Or it may be
drawing in gas much faster from the
space between galaxies. Finkelstein
hopes that follow-up observations
will now answer the question.
The search for distant galaxies is
driven by the aim to find, ultimately,
the first ones to form in the universe.
These galaxies could have been home
to stars that produced the first batch
of natural elements heavier than
helium when they exploded at the end
of their lives.
Astronomers may struggle to find
more distant galaxies with telescopes
operating today. But towards the end
of the decade, Nasa expects to launch
the James Webb Space Telescope ,
which has been designed to look
further back into the history of the
universe.
• This article was amended on 24
October 2013. The original stated that
the newly measured galaxy was 40bn
to 50bn times lighter than the Milky
Way. This has been corrected.
