Visual Binary Stars

These movies simulate the orbit of a visual binary star pair consisting of an F0v primary and M0v secondary. The orbital plane of the two is in the plane of the sky. The two stars have a mass ratio of about 3.6, appropriate for stars of this type.

Circular Orbit

Circular Orbit

520Kb QuickTime Movie
60Kb MPEG Movie
216Kb Animated GIF

This movie shows the two stars in circular orbits about their center of mass (marked with the green dot). Two orbits are shown, with the orbit traced as a white line. Both stars move at a uniform speed around the center of mass, the more massive, blueish F0v star moves less as it is closer to the center-of-mass than the less massive, reddish M0v star.

Elliptical Orbit (e=0.4):

Elliptical Orbit

512Kb QuickTime Movie
58Kb MPEG Movie
208Kb Animated GIF

This movie shows the two stars in elliptical orbits about their center of mass, with an orbital eccentricity of 0.4. Watch how both stars noticeably speed up and slow down as they pass periastron (closest approach to the C-of-M) and apastron (farthest from C-of-M), respectively, thus obeying Kepler's Second Law (equal areas in equal times) the same as the planets in the Solar System.

[Credit: R. Pogge, OSU]

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Prof. Richard Pogge (

Updated: 1998 January 10 [rwp]

Copyright 1998 Richard W. Pogge, All Rights Reserved.