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
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
detected a high-eccentricity low-mass companion to HD 89744.
detected a multiple planetary system around the star Upsilon Andromedae.
detected a planet around the star rho Coronae Borealis.
confirmed the presence of a 3.9 Jupiter mass planet around the star tau Bo÷tis.
confirmed the presence of a 0.5 Jupiter mass planet around the star 51 Pegasi.
Presented at the 194th AAS meeting:
"Evidence for a System of planets orbiting upsilon Andromedae",
a poster presentation showing the evidence for a system of 3 giant planets
around the star Upsilon Andromedae and the results of dynamical stability calculations to further contrain the properties
of the system.
Published in The Astrophysical Journal Letter (v. 494, p.
"A Search for Line Shape and Depth Variations in
51 Pegasi and Tau Bo÷tis" ,
where our analysis of spectroscopic observations of 51 Pegasi and tau Bo÷tis
with the AFOE show no periodic changes in the shapes of their line profiles; these results for 51 Peg are in significant conflict
with those reported by Gray and Hatzes (1997).