Combining data from several observatories, astronomers have now labeled NGC 6872 as the largest known spiral galaxy. The barred spiral galaxy was known to be huge, but new data indicates that it's the largest we've ever seen, some 522,000 light-years across, five times larger than our Milky Way.Its central bar, which gives the galaxy type its name, is some 26,000 light-years across, about as far out as the sun is from the center of the Milky Way.
Scientists used data from NASA's Galaxy Evolution Explorer mission to spot a new region of the galaxy, only visible in ultraviolet light.
Combined with visible light data from the European Southern Observatory's Very Large Telescope along with data from the Two Micron All Sky Survey, and NASA's Spitzer Space Telescope, a team astronomers from several countries think they have enough evidence to crown the new king.
NGC 6872, like most other large galaxies including our own, has grown to the gargantuan size by gobbling up smaller galaxies.
It's happening now too, NGC 6872 is interacting with the smaller IC 4970 which is five times lighter, seen on top of the large barred spiral galaxy in the image above.
Surprisingly, this interaction, rather than resulting in one even bigger galaxy, may have spun off enough material from NGC 6872 to create a new dwarf galaxy full of young stars and active stellar formation.
"The northeastern arm of NGC 6872 is the most disturbed and is rippling with star formation, but at its far end, visible only in the ultraviolet, is an object that appears to be a tidal dwarf galaxy similar to those seen in other interacting systems," Duilia de Mello, a professor of astronomy at Catholic University and a member of the team presenting the new data, said.