Astronomy Picture of the Day

Explanation: These three bright nebulae are often featured in telescopic tours of the constellation Sagittarius and the crowded starfields of the central Milky Way. In fact, 18th century cosmic tourist Charles Messier cataloged two of them; M8, the large nebula left of center, and colorful M20 near the bottom of the frame The third, NGC 6559, is right of M8, separated from the larger nebula by dark dust lanes. All three are stellar nurseries about five thousand light-years or so distant. The expansive M8, over a hundred light-years across, is also known as the Lagoon Nebula. M20's popular moniker is the Trifid. In the composite image, narrowband data records ionized hydrogen, oxygen, and sulfur atoms radiating at visible wavelengths. The mapping of colors and range of brightness used to compose this cosmic still life were inspired by Van Gogh's famous Sunflowers. Just right of the Trifid one of Messier's open star clusters, M21, is also included on the telescopic canvas.