Astronomy Picture of the Day . NGC 2403 in Camelopardalis . ... Some 10 million light-years distant and about 50,000 light-years across, the spiral galaxy also seems to have more than its fair share of giant star forming HII regions, marked by the telltale reddish glow of atomic hydrogen gas. ... Nix and Hydra were first introduced to human eyes in Hubble Space Telescope images from May 2005, as Pluto's second and third known moons. ... Sometimes it's night on the ground but day in the air. ...