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GREEN BANK -- A galaxy with no visible stars -- "potentially the faintest galaxy found to date" -- was discovered by researchers at the Green Bank Observatory, who have presented their findings at the annual meeting of the American Astronomy Society.
"While surveying hydrogen gas in Low Surface Brightness galaxies an astronomer made an unusual discovery," a Green Bank Observatory press release states. "(A total of) 350 unique galaxies were studied for this survey, and astronomers used several major radio telescopes around the world, including the National Science Foundation's Green Bank Telescope, the Arecibo Telescope, and the Nancay Radio Telescope.
"The goal was to determine the gas and dynamic masses of these ultra-diffuse galaxies. To do this, we observed them from several instruments, and many of them more than once," said Karen O'Neil, senior scientist of the Green Bank Observatory.
O'Neil said she discovered "an error" while examining a discrepancy between data from the Nancay Radio Telescope and the Green Bank Telescope.
"The GBT was accidentally pointed to the wrong coordinates and found this object. It's a galaxy made only out of gas -- it has no visible stars. Stars could be there, we just can't see them," O'Neils said.
Now known as J0613+52, this Low Surface Brightness galaxy is unlike others that have been observed before, she added.
"What we do know is that it's an incredibly gas rich galaxy. It's not demonstrating star formation like we'd expect, probably because its gas is too diffuse," O'Neil said. "At the same time, it's too far from other galaxies for them to help trigger star formation through any encounters.
"J0613+52 appears to be both undisturbed and underdeveloped. This could be our first discovery of a nearby galaxy made up of primordial gas."
O'Neil said a deep optical image in multiple bands could reveal more, and push the limits on observable stellar light, but the galaxy's low surface density of gas makes it very difficult, or even impossible, to observe at other wavelengths.
"A full sky survey by an extremely sensitive instrument like the Green Bank Telescope could uncover more of these objects," she said.
The Green Bank Observatory is a major facility of the National Science Foundation and is operated by Associated Universities, Inc. The first national radio astronomy observatory in the U.S., it is home to the 100-meter Green Bank Telescope, the largest fully-steerable radio telescope in the world.