Astronomy Picture of the Day

Explanation: In the vast Orion Molecular Cloud complex, several bright blue nebulas are particularly apparent. Pictured here in the center are two of the most prominent reflection nebulas - dust clouds lit by the reflecting light of bright embedded stars. The more famous nebula is M78, in the image center, cataloged over 200 years ago. To its upper left is the lesser known NGC 2071. Astronomers continue to study these reflection nebulas to better understand how interior stars form. The overall red glow is from diffuse hydrogen gas that covers much of the Orion complex that spans much of the constellation of Orion. Nearby in the greater complex, which lies about 1,500 light years away, are the Orion Nebula, the Horsehead Nebula, and Barnard's Loop -- partially seen here as the white band on the upper left.