A Mega-Galaxy - Bigger Than Any Other Known So Far

NASA's GALEX Reveals the Largest-Known Spiral Galaxy - Press release states, "This composite of the giant barred spiral galaxy NGC 6872 combines visible light images from the European Southern Observatory's Very Large Telescope with far-ultraviolet (1,528 angstroms) data from NASA's GALEX and 3.6-micron infrared data acquired by NASA's Spitzer Space Telescope. A previously unsuspected tidal dwarf galaxy candidate (circled) appears only in the ultraviolet, indicating the presence of many hot young stars."

It's always been known to be a huge galaxy, but recently NASA determined that, "Measuring tip-to-tip across its two outsized spiral arms, NGC 6872 spans more than 522,000 light-years, making it more than five times the size of our Milky Way galaxy." That makes it the largest known spiral galaxy to date.