Astronomers
have found nine of the faintest, tiniest and most compact galaxies ever seen.
The little
objects are hundreds to thousands of times smaller and vastly younger than our
Milky Way, lending support to a "building block" theory in which hundreds of
the tiny galaxies merge together and form larger bodies of stars.
"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.
Pirzkal
said their petite mass, observed by the Hubble Space Telescope and confirmed by
the Spitzer Space Telescope, shows these galaxies are some of the smallest
building blocks of the universe, aside from stars themselves.
The two
telescopes saw light emitted from the galaxies only 1 billion years after the
theoretical Big Bang, giving a
rare glimpse into the past. Sangeeta Malhotra, an astronomer at Arizona State University who helped make the discovery, said the absence of infrared light
in the sensitive Spitzer images showed the stars are first-generation and only
a few million years old.
"These
are truly young galaxies without an earlier generation of stars," Malhotra
said.
Hubble
detected hot blue stars within the nine galaxies, indicating that the youthful
stars are in the process of turning hydrogen and helium into heavier elements
like carbon, oxygen and silicon necessary for
planet-building--and life. The astronomers speculated, however, that such
stars probably haven't begun to "pollute" space with the crucial
elements forging within their cores.
The
development of three of the galaxies appears to be slightly disrupted; rather
than taking on a rounded-blob shape typical of the youngest galaxies, they're stretched
into tadpole-like forms. Astronomers think it may signal their first fusion
with neighboring galaxies to form larger, cohesive structures.
The
galaxies were observed in the Hubble Ultra Deep Field (HUDF) image 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.
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