Three facts about today's picture of the day, of the spiral galaxy Messier 101:
Its name conveys that it was featured in French astronomer Charles Messier's catalog of celestial objects. In fact, it was one of the last entries.
It was observed by William Parsons, 3rd Early of Rosse, with his enormous telescope. (The Leviathan of Parsontown, as it's called, was the world's largest telescope until the early 20th-century.)
Twice as large as the Milky Way, the colors here emerge from a composite of many telescopic images and wave-lengths: from the Chandra X-ray Observatory, purple; from the Galaxy Evolution Explorer, blue; from the Hubble Space Telescope, yellow; from the Spitzer Space Telescope, red.
Below, recent Pictures of the Day: