This
story was updated at 1:43 p.m. EST.
A stellar
nursery tucked away in a distant cloud of interstellar gas has given
astronomers a glimpse of a new way that galaxies can form.
Hints of
the star birth were spotted in an ancient gas cloud known as the
Leo Ring, which appears to lack the vital heavy elements and dark
matter that astronomers normally expect to see in growing galaxies.
The Leo
Ring find suggests that some galaxies may not need those core ingredients to
grow. Astronomers used observations from NASA's ultraviolet Galaxy
Evolution Explorer (GALEX) spacecraft to make the discovery.
"This
demonstrates the tremendous power of observing the ultraviolet from space," said
study co-author Mark Seibert, an astronomer with the Carnegie Observatories.
"By discovering star formation in what is likely a new class of dwarf galaxy
the Galaxy Evolution Explorer observatory is certainly living up to its name."
Discovered
in 1983, the Leo Ring is a vast cloud of hydrogen and helium locked in orbit
around two distant galaxies in the constellation Leo. Since the cloud is nearly
invisible to optical telescopes, it was first spotted by radio astronomers and
subsequent attempts to plumb its depths for star formation have come up empty.
NASA's
GALEX observatory, however, is equipped with sensitive detectors that scan the
sky in the ultraviolet range. The spacecraft spotted clouds of star-forming
regions within the Leo Ring that astronomers believe to be dwarf galaxies.
Since
previous measurements of masses and speeds of objects within the Leo Ring
suggest it lacks any significant source
of dark matter, researchers are unsure how the dwarf galaxies have managed
to form.
Dark matter
is a mysterious substance thought to make up 85 percent of the entire supply of
matter in the universe and serve as the foundation atop which galaxies mature. The
stuff is invisible, with astronomers inferring its existence from its
gravitational influence that aids galaxy formation.
Researchers
said that it is possible that the gas inside the Leo Ring could be the
untouched leftovers from the beginning of the universe. If so, its dwarf
galaxies could be built from nearly pure hydrogen and helium, and represent how
galaxies formed during the early universe when heavier elements were
unavailable.
The
research will appear in the Feb. 19 issue of the journal Nature.
Astronomer David Thilker of Johns Hopkins University led the study, with
Seibert and fellow Carnegie Observatories astronomer Barry Madore serving as
co-investigators and co-authors.
"The
next phase is to follow up these objects with deep imaging and spectroscopy
from the ground," said Madore, who is also a co-investigator with NASA's GALEX
mission. "An observing run on Carnegie's 6.5m Baade telescope is already
scheduled for this spring."
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