Light Traveled Some 13 Billion Years To Space Telescope's
Sensors
Astronomers say they have pushed NASA's Hubble Space Telescope
to its limits by finding what is likely to be the most distant
object ever seen in the universe. The object's light traveled 13.2
billion years to reach Hubble, roughly 150 million years longer
than the previous record holder. The age of the universe is thought
to be approximately 13.7 billion years.
The tiny, dim object is a compact galaxy of blue stars that
existed 480 million years after the big bang. More than 100 such
mini-galaxies would be needed to make up our Milky Way. The new
research offers surprising evidence that the rate of star birth in
the early universe grew dramatically, increasing by about a factor
of 10 from 480 million years to 650 million years after the big
bang.
"NASA continues to reach for new heights, and this latest Hubble
discovery will deepen our understanding of the universe and benefit
generations to come," said NASA Administrator Charles Bolden, who
was the pilot of the space shuttle mission that carried Hubble to
orbit. "We could only dream when we launched Hubble more than 20
years ago that it would have the ability to make these types of
groundbreaking discoveries and rewrite textbooks."
Astronomers don't know exactly when the first stars appeared in
the universe, but every step farther from Earth takes them deeper
into the early formative years when stars and galaxies began to
emerge in the aftermath of the big bang. "These observations
provide us with our best insights yet into the earlier primeval
objects that have yet to be found," said Rychard Bouwens of the
University of Leiden in the Netherlands. Bouwens and Illingworth
report the discovery in the Jan. 27 issue of the British science
journal Nature.
This observation was made with the Wide Field Camera 3 starting
just a few months after it was installed in the observatory in May
2009, during the last NASA space shuttle servicing mission to
Hubble. After more than a year of detailed observations and
analysis, the object was positively identified in the camera's
Hubble Ultra Deep Field-Infrared data taken in the late summers of
2009 and 2010.
The object appears as a faint dot of starlight in the Hubble
exposures. It is too young and too small to have the familiar
spiral shape that is characteristic of galaxies in the local
universe. Although its individual stars can't be resolved by
Hubble, the evidence suggests this is a compact galaxy of hot stars
formed more than 100-to-200 million years earlier from gas trapped
in a pocket of dark matter. "We're peering into an era where big
changes are afoot," said Garth Illingworth of the University of
California at Santa Cruz. "The rapid rate at which the star birth
is changing tells us if we go a little further back in time we're
going to see even more dramatic changes, closer to when the first
galaxies were just starting to form."
The proto-galaxy is only visible at the farthest infrared
wavelengths observable by Hubble. Observations of earlier times,
when the first stars and galaxies were forming, will require
Hubble's successor, the James Webb Space Telescope (JWST). The
hypothesized hierarchical growth of galaxies -- from stellar clumps
to majestic spirals and ellipticals -- didn't become evident until
the Hubble deep field exposures. The first 500 million years of the
universe's existence, from a z of 1000 to 10, is the missing
chapter in the hierarchical growth of galaxies. It's not clear how
the universe assembled structure out of a darkening, cooling
fireball of the big bang. As with a developing embryo, astronomers
know there must have been an early period of rapid changes that
would set the initial conditions to make the universe of galaxies
what it is today. "After 20 years of opening our eyes to the
universe around us, Hubble continues to awe and surprise
astronomers," said Jon Morse, NASA's Astrophysics Division director
at the agency's headquarters in Washington. "It now offers a
tantalizing look at the very edge of the known universe -- a
frontier NASA strives to explore."