Astronomy Picture of the Day

Explanation: The best known asterism in northern skies, The Big Dipper is easy to recognize, though some might see The Plough. Either way, the star names and the familiar outlines will appear in this thoughtfully composed 24 frame mosaic when you slide your cursor over the image. Dubhe, alpha star of the dipper's parent constellation Ursa Major is at the upper right. Together with beta star Merak below, the two form a line pointing the way to Polaris and the North Celestial Pole off the top edge of the field. Notable too in skygazing lore Mizar, second star from the left in the dipper's handle, forms a vision-testing visual double star with apparently close Alcor. Also identified in the famous star field are Messier catalogue objects. Download the higher resolution image to hunt for exquisite views of some of Messier's distant spiral galaxies and a more local owl.