For the first time in almost a decade, sky-watchers this week will be able to see all five naked-eye planets over the course of one night for several nights in a row. The classical naked-eye planets—Mercury, Venus, Mars, Jupiter, and Saturn—can be seen easily without optical aids and so have been known since ancient times.
Hubble Space Telescope: Kepler's Supernova Remnant (close-up, visible-light data) | Four hundred years ago a "new star" appeared in the western sky, rivaling the brilliance of the nearby planets. In fact this 'new star' was a supernova, now named Kepler's supernova, and was the last such object seen to explode in our Milky Way galaxy. Seen here are some of its remains.
Orrery - 10,000 Year Clock - The Long Now# The Orrery is an eight-foot tall planetary display. It shows the relative position of the six human-eye visible planets (Mercury through Saturn). The lower six layers are a mechanical-binary calculation engine, each with a geneva output to a gear that rotates a corresponding planet. Each layer is calculating a fraction of the planetary orbits to 28 bits of accuracy.