by Elizabeth Howell
The European Southern Observatory's Muse instrument
Very Large Telescope in Chile
captured this view of galaxies in a region of sky
included in the Hubble Space Telescope's Ultra Deep Field survey.
discovered 72 never-before-seen galaxies in the region.
Credit: ESO/MUSE HUDF Collaboration
Astronomers have found 72 potential galaxies hiding in plain sight
inside a vast patch of the sky previously observed by the Hubble
Space Telescope (HST).
The discovery not only
gives astronomers new targets to study, but also will aid studies of
star motion and formation and other properties of old galaxies, the
The new study was performed by the
MUSE instrument on the European
Southern Observatory's Very Large Telescope in Chile.
the newfound galaxies while measuring the distances and properties
of 1,600 galaxies captured by the Hubble Space Telescope during its
Ultra Deep Field survey.
The 72 newfound galaxies shine in
Lyman-alpha light, which is a
particular wavelength of ultraviolet light.
Because the galaxies are
receding from us, their wavelength was stretched from ultraviolet to
visible, or near-infrared.
The discoveries were made in the Hubble Ultra Deep Field,
which is a tiny region of the sky in the southern
constellation Fornax (the Furnace).
The Hubble data were
originally obtained in 2004, two years after NASA space shuttle
astronauts visited the space telescope to install the Advanced
Camera for Surveys (ACS)
and perform other needed maintenance.
Using ACS, Hubble peered at a small region of the sky and found
galaxies that had formed less than 1 billion years after
the Big Bang, which kick-started
the universe (the Big Bang took place about
billion years ago, making those galaxies more than 12.8
billion years old.)
"MUSE can do
something that Hubble can't - it splits up the light from every
point in the image into its component colors to create a
This allows us to
measure the distance, colors and other properties of all the
galaxies we can see - including some that are invisible to
Hubble itself," stated Roland Bacon, who led the survey team and
is also an astrophysicist at the Center for Astrophysics
Research of Lyon at the University of Lyon in France.
This image shows an improved version
Hubble Ultra Deep Field from 2012
by the Hubble Space Telescope.
Credit: NASA, ESA, R. Ellis (Caltech),
HUDF 2012 Team
MUSE is a spectroscopic instrument, meaning it measures light
emitted, absorbed or scattered in space.
Using spectroscopy, astronomers can learn about stars, galaxies and
other objects, including properties such as how fast the objects are
moving and what elements they are made of.
MUSE recently underwent
an adaptive-optics upgrade, which could help with future studies of
old galaxies, Roland Bacon added.
The new work resulted in 10 science papers that will be published in
a special issue of the journal Astronomy & Astrophysics.
"MUSE has the unique
ability to extract information about some of the earliest
galaxies in the universe - even in a part of the sky that is
already very well-studied," stated Jarle Brinchmann, lead author
of one of the papers.
"We learn things about these galaxies that [it] is only possible
[to learn] with spectroscopy, such as chemical content and
internal motions - not galaxy by galaxy, but all at once for all
the galaxies," added Brinchmann, who is an astronomer at Leiden
University in the Netherlands and the Institute of Astrophysics
and Space Sciences at CAUP (Center for Astrophysics of the
University of Porto) in Portugal.
This compound image of the Hubble Ultra Deep Field region
depicts glowing halos of gas around galaxies
discovered by the Muse instrument on the
European Southern Observatory's Very Large Telescope.
Credit: ESO/MUSE HUDF team
Astronomers also found hydrogen halos in old galaxies, which could
provide more information about how material leaves and enters
galaxies formed early in the universe's history.
directions could include looking at star formation, galactic winds,
galaxy mergers or even a phenomenon known as cosmic reionization.
That phenomenon explains how light returned to a dark universe
billions of years ago.
"First light" in the
universe was roughly 380,000 years after the Big Bang, when the
cosmos cooled down and fundamental particles were able to combine
However, once these
combinations ceased, the universe entered a dark age, because there
was no other light available - the first stars weren't shining yet.
between 150 million years and 650 million years after the Big Bang,
when the first stars and galaxies were formed from collapsing groups
of gas, producing light in the universe again.