Greatest Planetary Elongation
Greatest Planetary Elongation
Venus is known both as the morning star and the evening star because it is often easily visible either before sunrise or after sunset. But how far away from the Sun can it be, as seen from Earth? This maximum angle is known in astronomy as the greatest elongation. This Demonstration provides a visualization for planetary elongation for the three nearest planets. Adjust the angle slider to move the planet around the Sun—or better, click the + to open the animation controls and then the play button to make the planet circle the Sun automatically. Various options for the display are given, and the last two buttons reveal the maximum angle numerically and graphically.