Robert Makemson Guide to Astronomy in Jacksonville

Extra Solar Planet Detection

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Observational Physics
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Outer Limits of Space
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Virtual Interactive Solar-system Telescope


The Extrasolar Planets Encyclopaedia

Extrasolar Planet Detection with the AFOE

Detection of a high-eccentricity low-mass companion to HD 89744


Extrasolar planet detection is the search for planets around other stars than our Sun. Several techniques are being used to detect planets around other suns; they are discussed in a Scientific American Exploration Web page.

The AFOE has been designed to provide the required precison and stability to detect the wobble induced on the star by the presence of a planet.

Indeed, both the planet and the star revolve around their common center of gravity. While the center of gravity is very close to the center of the star, it is not exactly at the center of the star.

Therefore the star wobbles around the center of gravity with the same period as the planet. The more massive the planet and the closer the orbit the larger will be the amplitude of the wobble.

By measuring the doppler shift caused by the wobble of the star on the light it emits, we can detect such a periodic motion.

This wobble is very small, therefore very stable and precise measurements are needed to make such a detection. The amplitude if the wobble induced by Jupiter on the Sun is 13 meters per second, or 29 miles per hour (1 m/s is 2.237 mph).

Animations for some simulations of orbit are now available.


The AFOE has developed a planet detection program since 1992. As of 1995, the instrument configuration became stable enough to achieve the required precision.

The AFOE extrasolar program has since