About 250 million light years away from our universe, an enormous, bizarre galaxy possibly formed from the parts of other galaxies, was found using NASA telescopes and other observatories.
A new study to be published in the Astrophysical Journal reveals the secret of UGC 1382, a galaxy that had originally been thought to be old, small and typical. Instead, 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, Pasadena, California. “It is so delicate that a slight nudge from a neighbor would cause it to disintegrate.”
Seibert and Lea Hagen, a graduate student at Pennsylvania State University, University Park, came upon this 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.
But while looking at images of galaxies in ultraviolet light through data from NASA’s Galaxy Evolution Explorer (GALEX), a behemoth began to emerge from the darkness.
The galaxy UGC 1382 has been found to be larger than previously thought. In the image at left, UGC 1382 appears to be a simple elliptical galaxy, based on optical data from the Sloan Digital Sky Survey (SDSS) but spiral arms emerged when incorporated ultraviolet data from the Galaxy Evolution Explorer (GALEX) and deep optical data from SDSS, as seen in the middle image.
Combining it with low-density hydrogen gas (in green), detected at radio wavelengths by the Very Large Array, scientists discovered that UGC 1382 is a giant and one of the largest isolated galaxies ever known.
“We saw spiral arms extending far outside this galaxy, which no one had noticed before, and which elliptical galaxies should not have,” said Hagen, who led the study. “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 other telescopes: the Sloan Digital Sky Survey, the Two Micron All-Sky Survey (2MASS), NASA’s Wide-field Infrared Survey Explorer (WISE), the National Radio Astronomy Observatory’s Very Large Array and Carnegie’s du Pont Telescope at Las Campanas Observatory. After GALEX revealed previously unseen structures to the astronomers, optical and infrared light observations from the other telescopes allowed the researchers to build a new model of this mysterious galaxy.
As it turns out, UGC 1382, at about 718,000 light-years across, is more than seven times wider than the Milky Way. It is also one of the three largest isolated disk galaxies ever discovered, according to the study. This galaxy is a rotating disk of low-density gas. Stars don’t form here very quickly because the gas is so spread out.
But 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.
“By understanding this galaxy, we can get clues to how galaxies form on a larger scale, and uncover more galactic neighborhood surprises,” Hagen said.