The Largest-Known Spiral Galaxy

The spectacular barred spiral galaxy NGC 6872 has ranked among the biggest stellar systems for decades. This enormous spiral is 522,000 light-years across from the tip of one outstretched arm to the tip of the other, making it about five times the size of our home galaxy, the Milky Way. The galaxy's unusual size and appearance stem from interaction with a much smaller disk galaxy named IC 4970 (circled in yellow), which has only about one-fifth the mass of NGC 6872. This previously unsuspected tidal dwarf galaxy candidate appears only in the ultraviolet. The odd couple is located 212 million light-years from Earth in the southern constellation Pavo. This composite image of the giant barred spiral galaxy NGC 6872 combines ultraviolet data from NASA's Galaxy Evolution Explorer (GALEX) and infrared data acquired by NASA's Spitzer Space Telescope with visible light images from the European Southern Observatory's Very Large Telescope. Images of lower resolution from the Digital Sky Survey were used to fill in marginal areas not covered by the other data.

See www.galex.caltech.edu/media/glx2013-01r_img01.html