This image of the Hubble Ultra-Deep Field is a small part of the deepest infrared image ever taken of the universe. The small blue box outlines the area where astronomers found what may be the most distant galaxy ever seen, 13.2 billion light-years away, meaning its light was emitted just 480 million years after the Big Bang. It is small and very faint and is shown separately in the larger box. The galaxy is shown as blue because it emitted very blue light due to its high rate of star birth, although by the time the light reached Hubble it had been stretched into the infrared by the expansion of space, giving it a redshift value of about 10. Its official name is UDFj-39546284, but astronomers refer to it as the “redshift 10 galaxy candidate.” Credit: NASA, ESA, Garth Illingworth (University of California, Santa Cruz) and Rychard Bouwens (University of California, Santa Cruz and Leiden University) and the HUDF09 Team. |
Astronomers have
pushed NASA’s Hubble Space Telescope to it limits by finding what they believe
to be the most distant object ever seen in the universe—at a distance of 13.2
billion light years, some 3% of the age of universe. This places the object
roughly 150 million light years more distant than the previous record holder.
The observations provide the best insights yet into the birth of the first
stars and galaxies and the evolution of the universe. The research is published
in the 27th January edition of Nature.
The dim object is a
compact galaxy made of blue stars that existed only 480 million years after the
Big Bang. It is tiny. Over one hundred such mini galaxies would be needed to
make up our Milky Way.
Co-author Ivo Labbé
of the Carnegie Observatories puts the findings into context: “We are thrilled
to have discovered this galaxy, but we’re equally surprised to have found only
one. This tells us that the universe was changing very rapidly in early times.”
Previous searches had
found 47 galaxies at somewhat later times, when the universe was about 650
million years old. The rate of star birth therefore increased by about ten
times in the interval from 480 million years to 650 million years. “This is an
astonishing increase in such a short period, happening in just 1% of the age of
the universe,” says Labbé.
“These observations
provide us with our best insights yet into the earliest primeval objects yet to
be found,” adds Rychard Bouwens of the University
of Leiden in the Netherlands.
Astronomers don’t
know exactly when the first stars appeared in the universe, but every step back
in time takes them deeper into the early universe’s “formative years” when
stars and galaxies were just beginning to emerge in the aftermath of the Big
Bang.
“We’re moving into a
regime where there are big changes afoot. And what it tells us is that if we go
back another couple hundred million years toward the Big Bang we’ll see
absolutely dramatic things happening. That will be the time where the first
galaxies really are starting to get built up,” says Garth Illingworth of the University of California
at Santa Cruz.
The even more distant
proto galaxies will require the infrared vision of NASA’s James Webb Space
Telescope, which is the successor to Hubble, and next-generation ground-based
telescopes, such as the Giant Magellan Telescope. These new facilities, planned
for later this decade, will provide confirming spectroscopic measurements of
the tremendous distance of the object being reported today.
After over a year of
detailed analysis, the galaxy was positively identified in the Hubble Ultra
Deep Field – Infrared (HUDF-IR) data taken in the late summer of both 2009 and
2010. These observations were made with the Wide Field Planetary Camera 3
(WFPC3) starting just a few months after it was installed into the Hubble Space
Telescope in May of 2009, during the last NASA space shuttle servicing mission
to Hubble.
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, such as the Milky Way. Though individual stars can’t be
resolved by Hubble, the evidence suggests that this is a compact galaxy of hot
stars that first started to form over 100 to 200 million years earlier in a
pocket of dark matter.
The proto galaxy is
only visible at the farthest infrared wavelengths observable by Hubble. This
means that the expansion of the universe has stretched its light farther that
any other galaxy previously identified in the HUDF-IR, to the very limit of
Hubble’s capabilities.
Astronomers plumb the
depths of the universe by measuring how much the light from an object has been
stretched by the expansion of space. This is called redshift value or “z.”
Before Hubble was launched, astronomers could only see galaxies out to a z
approximately 1, corresponding to 6 billion years after the Big Bang. The
Hubble Deep Field taken in 1995 leapfrogged to z=4, or roughly 90 percent of
the way back to the beginning of time. The new Advanced Camera and the Hubble
Ultra Deep Field pushed back the limit to z~6 after the 2002 servicing mission.
Hubble’s first infrared camera, the Near Infrared Camera and Multi Object
Spectrometer reached out to z=7. The WFC3/IR reached back to z~8, and now
plausibly has penetrated for the first time to z=10 (about 500 million years
after the Big Bang). The Webb Space Telescope is expected to leapfrog to z~15,
and possibly beyond. The very first stars may have formed between z of 30 to
15, or 100 to 250 million years post Big Bang.
The hypothesized
hierarchical growth of galaxies—from stellar clumps to majestic spirals—didn’t
become evident until the Hubble Space Telescope deep field exposures. The first
500 million years of the universe’s existence, from a z of 1000 to 10 is now
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 that exist today. Astronomers eagerly await the new space
and ground-based telescopes to find out!
