Astronomy Picture of the Day

Explanation: How far can you see? The Andromeda Galaxy 2.5 million light years away is the most distant object easily seen by the unaided eye. Other apparent denizens of the night sky, stars, clusters, and nebulae, typically range from a few hundred to a few thousand light-years away and lie well within our own Milky Way Galaxy. Also known as M31, the Andromeda Galaxy is the faint smudge near top centre of this Earth and skyscape, taken from eastern Italy, near Monte Conero on the Adriatic sea coast. From a few centimetres to a few million light-years, the picture demonstrates a stunning range of vision. Though galaxy and seaside rocks could be seen with the eye on that clear summer night, no camera captured this view in a single exposure. Because the stars trailed above the horizon while the picture was made, separate exposures tracking the stars were combined with one of rocks and cliffs made with the camera steadied to create the tantalizing scene.