Pasadena Astronomers Discover Bizarre "Frankenstein" Galaxy

Pasadena, CA -- Astronomers have uncovered an enormous, bizarre "Frankenstein" galaxy, possibly formed from the parts of other galaxies, about 250 million light-years away from Earth, NASA's Jet Propulsion Laboratory reported today.

UGC 1382 had originally been thought to be "old, small and typical," according to JPL. But scientists using data from NASA telescopes and other observatories "have discovered that the galaxy is 10 times bigger than previously thought and, unlike most galaxies, its insides are younger than its outsides, almost as if it had been built using spare parts."

"This rare, 'Frankenstein' galaxy formed and is able to survive because it lies in a quiet little suburban neighborhood of the universe, where none of the hubbub of the more crowded parts can bother it," said Mark Seibert of the Observatories of the Carnegie Institution for Science in Pasadena.

"It is so delicate that a slight nudge from a neighbor would cause it to disintegrate," said Seibert, co-author of a study to be published in the Astrophysical Journal.

Seibert and Lea Hagen, a graduate student at Pennsylvania State University who led the study, stumbled upon the galaxy by accident. They had been looking for stars forming in run-of-the-mill elliptical galaxies, which do not spin and are more three-dimensional and football-shaped than flat disks.

Astronomers originally thought that UGC 1382 was one of those, according to Hagen. But while looking at images of galaxies in ultraviolet light through data from NASA's Galaxy Evolution Explorer (GALEX), they "saw spiral arms extending far outside this galaxy, which no one had noticed before, and which elliptical galaxies should not have," she said. "That put us on an expedition to find out what this galaxy is and how it formed."

Researchers then looked at data of the galaxy from five other telescopes. Optical and infrared light observations from the other telescopes allowed the researchers to build a new model of the mysterious galaxy.

UGC 1382, at about 718,000 light-years across, is more than seven times wider than the Milky Way and is one of the three largest isolated disk galaxies ever discovered, according to the study.

The galaxy is a rotating disk of low-density gas, and stars don't form there very quickly because the gas is so spread out.

The astronomers said the biggest surprise was how the relative ages of the galaxy's components appear backwards. In most galaxies, the innermost portion forms first and contains the oldest stars. As the galaxy grows, its outer, newer regions have the youngest stars, but not so with UGC 1382.

"The center of UGC 1382 is actually younger than the spiral disk surrounding it," Seibert said. "It's old on the outside and young on the inside. This is like finding a tree whose inner growth rings are younger than the outer rings."

According to JPL, the "unique galactic structure may have resulted from separate entities coming together, rather than a single entity that grew outward. In other words, two parts of the galaxy seem to have evolved independently before merging -- each with its own history."

More galaxies like this may exist, but more research is needed to look for them, the astronomers said. "By understanding this galaxy, we can get clues to how galaxies form on a larger scale, and uncover more galactic neighborhood surprises," Hagen said.

The GALEX mission, which ended in 2013 after more than a decade of scanning the skies in ultraviolet light, was led by scientists at Caltech in Pasadena. JPL, also in Pasadena, managed the mission and built the science instrument.

City News Service; Photos: Images of UGC 1382 courtesy of NASA.