Scale: 10¹³ meters = 10 Tm = 10 terameters: Light takes ~8 hours to cross this picture.

The Solar System

If you knew exactly where to look with a powerful telescope -- and took pictures several days, weeks, or months apart -- you might be able to find the four giant planets moving against the background of fixed stars. From the inside out we are looking at the orbits of Jupiter, Saturn, Uranus, and Neptune. The highly elliptical orbit belongs to Pluto.

You may notice that the Sun is no longer exactly in the center of the image. We have moved close enough to Earth to be able to tell that we are not headed directly toward the Sun. The Sun is much too bright at this distance to be able to discern any of the small, inner, rocky planets.

In the last few years, four spacecraft have passed beyond the orbit of Pluto on their own journeys to the stars: Pioneers 10 and 11, and Voyagers 1 and 2. Pioneer 10 is farthest away at a distance of 10.3 terameters (over nine light hours). It is headed in the direction of Taurus toward the bright star of Aldebaran, 68 light years away -- arriving in about two million years....