NASA Space Telescopes Find 'Lego-Block' Galaxies in Early Universe
NASA's Hubble and Spitzer space telescopes have joined forces to
discover nine of the smallest, faintest, most compact galaxies ever
observed in the distant universe. Blazing with the brilliance of millions
of stars, each of the newly discovered galaxies is 100 to 1,000 times smaller
than our Milky Way galaxy.
"These are among the lowest mass galaxies ever directly observed in the
early universe," said Nor Pirzkal of the Space Telescope Science Institute
in Baltimore, Md.
Image right: In this image of the Hubble Ultra Deep Field, several objects are identified as the faintest,
most compact galaxies ever observed in the distant universe. They are so far away that
we see them as they looked less than one billion years after the Big Bang. Image credit: NASA/StScI/ESA
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The conventional model for galaxy evolution predicts that small galaxies in
the early universe evolved into the massive galaxies of today by coalescing.
These nine Lego-like "building block" galaxies initially detected by Hubble
likely contributed to the construction of the universe as we know it.
Pirzkal was surprised to find that the galaxies' estimated masses were so small.
Hubble's cousin observatory, Spitzer, was called upon to make precise determinations
of their masses. The Spitzer observations confirmed that these galaxies are
some of the smallest building blocks of the universe.
These young galaxies offer important new insights into the universe's formative
years, just one billion years after the Big Bang. Hubble detected sapphire blue
stars residing within the nine pristine galaxies. The youthful stars are just a few
million years old and are in the process of turning Big Bang elements, primarily
hydrogen and helium, into heavier elements. The stars have probably not yet begun
to pollute the surrounding space with elemental products forged within their cores.
"While blue light seen by Hubble shows the presence of young stars, it is the absence
of red light in the sensitive Spitzer images that was conclusive in showing that
these are truly young galaxies without an earlier generation of stars," says Sangeeta
Malhotra of Arizona State University in Tempe, Ariz., one of the investigators.
The galaxies were first identified by James Rhoads of Arizona State University and
Chun Xu of the Shanghai Institute of Technical Physics in Shanghai, China, by their
prominent and energetic light coming from glowing hydrogen. Three of the galaxies
appear to be slightly disrupted; rather than being shaped like rounded blobs, they
appear stretched into tadpole-like shapes. This is a sign that they may be interacting
and merging with neighboring galaxies to form larger, cohesive structures.
The galaxies were observed in the well-known Hubble Ultra Deep Field with Hubble's
Advanced Camera for Surveys and the Near Infrared Camera and Multi-object Spectrometer.
Observations were also done with Spitzer's Infrared Array Camera and the European Southern Observatory's Infrared Spectrometer and Array Camera.
Pirzkal's main collaborators were Malhotra, Rhoads, Xu and the Grism Advanced Camera
for Surveys Program for Extragalactic Science team.
For images and additional information about these galaxies, visit:
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope
mission for NASA's Science Mission Directorate, Washington. Science operations are
conducted at the Spitzer Science Center at the California Institute of Technology,
also in Pasadena. Caltech manages JPL for NASA.
The Hubble Space Telescope is a project of international cooperation between NASA
and the European Space Agency. The Space Telescope Science Institute conducts Hubble
science operations. The institute is operated for NASA by the Association of Universities
for Research in Astronomy, Inc., Washington.
Media contact: Whitney Clavin/Jane Platt 818-354-4673/354-0880
Jet Propulsion Laboratory, Pasadena, Calif.
Ray Villard 410-338-4514
Space Telescope Science Institute, Baltimore, Md.