Photograph
Galaxy M33 HaLRGB
An astrophotograph of the spiral galaxy M33 revealing its blue arms and red regions of active star formation.
Beyond the frame
The reddish knots scattered along the spiral arms are enormous regions of ionized hydrogen where new stars are forming. The brightest of them, NGC 604, is so large that if it were placed at the distance of the Orion Nebula, it would cover a substantial area of the sky. These colored patches turn the image into a map of ongoing star formation across an entire galaxy.