Example to try

Astronomy 101/103

Cornell University

Terry Herter


You need a JAVA enabled browser to view this simulation. This simulation is a bit unstable and may bring down the machine you are running.


Allows you to set the masses, orbital separation, orbital eccentricity, the inclination angle to our line of sight, and the angle of the nodes of an orbiting star pair. You see the privileged (from above the orbit) and the earth view of the system (which depends on the inclination angle). The observed velocities of the two stars, and the Doppler shifted spectral lines (as seen against the combined continuum from the two stars) are also shown in the upper right box. The spectral lines associated with each star are indicated and the unshifted line positions are also marked. The movement of the spectral lines against the continuum has been greatly exaggerated for display purposes, and the difference in brightness of the two stars has been ignored.

We have the following definitions:

Mass 1 or Mass 2

The mass of each of the two stars.


The distance between the two stars in solar radii.


Eccentricity of the orbit

Inclination angle

Angle of the orbital plane of the stars to our line-of-sight.

  • 0o - face on
  • 90o - edge on

Note that this is opposite from the Eclipse simulation - we'll fix this in the future.

Node angle

Angle of the major axis as measured in the orbital plane (see privileged view)



Please note:

Play around by changing the values of the parameters. Be sure, however, to only change one at a time to see what effect it has on the motion and velocities we see.