Comet Halley was photographed superposed in front of the disk of our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap970517.html ] in 1986 by the Kuiper Airborne Observatory [ http://quest.arc.nasa.gov/lfs/lfshp.html ]. Comet Halley [ http://www.seds.org/nineplanets/nineplanets/halley.html ] is the bright white streak near this photograph's [ http://ails.arc.nasa.gov/Images/Astrobiology/AC86-0720-1.html ] center. Comet Halley [ http://antwrp.gsfc.nasa.gov/apod/ap961210.html ] is the most famous comet in history, and returns to the inner Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap961214.html ] every 76 years. Stars visible in our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap970315.html ] typically lie millions of times farther in the distance and orbit the Galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap970121.html ] every 250 million years. Billions of comets [ http://medicine.wustl.edu/~kronkg/comintro.html ] are thought to orbit our Sun [ http://antwrp.gsfc.nasa.gov/apod/ap970226.html ] but most do not get close enough for us to see. Similarly, billions of stars orbit our Milky Way [ http://csep10.phys.utk.edu/guidry/violence/ginfo1.html ]'s center but do not get close enough for us to see.