Discovery Suggests New Way Galaxies Might Form
NASA's GALEX observatory spotted dwarf galaxies (in circles) growing inside the Leo Ring of interstellar gas, a region that is invisible to optical telescope but visible to GALEX's ultraviolet-scanning instruments.
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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