Astronomy Picture of the Day

Explanation: Comet Halley was photographed superposed in front of the disk of our Milky Way Galaxy in 1986 by the Kuiper Airborne Observatory. Comet Halley is the bright white streak near this photograph's centre. Comet Halley is the most famous comet in history, and returns to the inner Solar System every 76 years. Stars visible in our Milky Way Galaxy typically lie millions of times further in the distance and orbit the Galactic centre every 250 million years. Billions of comets are thought to orbit our Sun but most do not get close enough for us to see. Similarly, billions of stars orbit our Milky Way's centre but do not get close enough for us to see.