Outer Solar System Viewer
Seven bodies are depicted here. The Sun (yellow) is at the center of the
diagram, and the gaseous planets Jupiter (orange), Saturn (orange),
Uranus (light blue), and Neptune (dark blue) follow nearly circular
orbits around the Sun. Pluto (gray), however, has a highly elliptical
orbit. During the 1980's and 1990's Pluto was closer to the Sun than
Neptune. You can change the orbit of the seventh object, a comet (red,
connected to Sun by yellow line), with the sliders underneath the
The Semimajor Axis, a, is measured in units of
Astronomical Units (AU). One AU is the distance from the Earth to the
The orbial Eccentricity, e, is unitless. This
parameter is a measure of the roundness of the orbit and can take on
any positive value.
The Longitude of pericenter, w (omega), is an
angle with units of degrees. Omega is measured from a reference
direction, here the positive x-axis (green line at 3 o'clock), to
pericenter (the closest approach of the orbit to the Sun).
- For e = 0, the orbit is a circle
- For 0 < e < 1, the orbit is an ellipse.
- For e > 1, the orbit is a hyperbola.
Created on Nov 22, 1998.