Astronomy Picture of the Day . ... Until the invention of the telescope, nobody really knew what the "Milky Way" was. ... Pluto is usually the most distant planet from the Sun but because of its elliptic orbit Pluto crossed inside of Neptune's orbit in 1979 and will cross back out again in 1999. ... Seen from the Pik Terskol Observatory in the northern Caucasus mountains, comet Hale-Bopp and the bright stars of the constellation Perseus hang above the snowy, moon-lit landscape. ... September 1999 . ...