FURTHER EVIDENCE FOR THE PLANET AROUND 51-PEGASI

The discovery(1) of a planet around the solar-type star 51 Pegasi mark ed a watershed in the search for extrasolar planets. Since then, seven other planets have been discovered(2-6), of which several have surpri singly short orbital periods, like the planet around 51 peg. These pla nets were detected using the indirect technique of measuring variation s in the Doppler shifts of lines in the spectra of the primary stars, But it is possible that regular oscillations of the stars themselves ( or other effects) could mimic the signature of the planets, particular ly the short-period planets, The apparent lack of spectral(7) and brig htness(8) variations, however, led to widespread acceptance that there is a planet around 51 Peg. This conclusion was challenged by the obse rvation(9) of systematic variations in the line shapes of 51 Peg, whic h suggest stellar oscillations(10). If these observations are correct, then there is no need to invoke a planet around 51 Peg to explain the data. Here we report observations of 51 Peg at a much higher spectral resolution than those in ref. 9, in which we find no evidence for sys tematic changes in the line shapes. The data are most consistent with a planetary companion to 51 Peg.