NASA Picture Shows Largest-Seen Spiral Galaxy


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Astronomers this week unveiled a new image of the largest spiral galaxy known to exist. A larger version of the image can be seen here.

The galaxy, named NGC 6872, was crowned with the title following an examination of archival data from NASA's Galaxy Evolution Explorer (GALEX) mission. From tip-to-tip NGC 6872 measures 522,000 light-years, or around five times the size of our Milky Way galaxy.

"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," said Rafael Eufrasio, lead scientist on the project and a research assistant at NASA's Goddard Space Flight Center.

NGC 6872's size, astronomers say, is due to its interaction with the smaller disk galaxy named IC 4970. They found that the stars in NGC 6872 are progressively older the closer to the center they are. That interaction may also have spawned a region that could become its own small galaxy, seen in the upper left-had portion of the image above. The youngest stars can be found in that region.

"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," said Duilia de Mello, team member on the research and a professor of astronomy at Catholic University.

In 2007 researchers developed a computer simulation that was able to reproduce the appearance of the NGC 6872 system. According to that model, IC 4970 would have made its closest approach to the giant galaxy around 130 million years ago, then toured the plane of the spiral disk in the same direction it rotates. Astronomers stated that the new observations are consistent with this scenario.