Spiral Galaxy Is The Largest Ever Measured
January 11, 2013

Researchers Accidentally Discover Largest Known Spiral Galaxy

redOrbit Staff & Wire Reports - Your Universe Online

While searching for data looking for star-forming regions around a galaxy located more than 200 million light years away, researchers have accidentally discovered that it is, in fact, the largest known spiral galaxy in the entire universe.

As reported Friday by BBC News reporter Jason Palmer, a research assistant from NASA´s Goddard Space Flight Center and colleagues from the Catholic University of America (CUA), the University of Sao Paulo (USP) in Brazil and the European Southern Observatory (ESO) in Chile were reviewing information from the Galaxy Evolution Explorer (GALEX) satellite pertaining to a galaxy known as NGC 6872 when they made the discovery.

NGC 6827, which is located approximately 212 million years from Earth in the constellation of Pavo, was already known to be one of the largest spiral galaxies in existence. However, after reviewing the data, lead scientist Rafael Eufrasio and colleagues found that it is 522,000 light-years across — more than five times the size of our galaxy, the Milky Way, according to Michael Rundle of the Huffington Post UK.

"Without GALEX's ability to detect the ultraviolet light of the youngest, hottest stars, we would never have recognized the full extent of this intriguing system," Eufrasio, who is also a doctoral student at CUA, said in a recent statement. He presented the team´s findings Thursday at a meeting of the American Astronomical Society (AAS) in Long Beach, California.

According to NASA, the strange size and appearance of NGC 6827 is likely due to a nearby lenticular galaxy known as IC 4970. The lens-shaped galaxy, which has just one-fifth the mass of NGC 6872, is believed to have crashed through the spiral recently (astronomically speaking, that is). They were clued into the true size of the galaxy after finding massive amounts of ultraviolet light from young stars, which they say might have resulted from the collision between the two galaxies.

"I was not looking for the largest spiral — it just came as a gift," Eufrasio told BBC News in an interview. He noted that the galaxy was “much larger than we thought” and that the collision between NGC 6872 and IC 4970 “splashed stars all over the place,” some even up to “500,000 light years away.”

“It shows the evolution of galaxies in the larger context of the Universe - how the large galaxies we had before were accreted from small clumps in the early Universe,” he added. “We're just seeing one example of two interacting galaxies but in the past that happened much more often — that's how the big [spiral galaxy] discs we have were probably formed. Putting that in a larger context, it's a very cool system.”

Catholic University astronomy professor Duilia de Mello explained that the northeastern arm of NGC 6872 was the most disturbed as a result of the collision, and at its far end — visible only in the ultraviolet spectrum — is what appears to be a tidal dwarf galaxy candidate. That potential new galaxy is brighter in ultraviolet than the rest of the galaxy, which suggests that many of its stars are less than 200 million years old.

Archival data from the ESO´s Very Large Telescope, the Two Micron All Sky Survey (2MASS), and NASA's Spitzer Space Telescope were also used in the study, according to the US space agency.