The First ever Direct Observation of an Extra-solar Planet This grayscale phase plot illustrates
the method of Cameron et al. for
detecting reflected-light signatures from extra-solar planets, using data secured with the WHT + UES in 1998 and 1999. The left-hand panel shows 145 residual velocity profiles of the tau Boo system, obtained by subtracting a model of the direct starlight from the data and averaging the profiles of the ~2300 spectral lines buried in the residual spectrum. The velocity scale is in the reference frame of the star, and time increases upward. The dotted paths indicate the velocity curve of a planet orbiting with an orbital inclination of 29° (left-hand panel) and 60° (right-hand panel). The right-hand panel shows the effect of adding the simulated spectrum of a planet with 1.4 Jupiter radii and Jupiter-like reflectivity to the original spectra. The simulated planet signature appears as a dark linear feature with an amplitude about 10–4 of the mean stellar continuum level, crossing from positive to negative velocity at phase 0.5 when the planet is on the far side of the star. The planetary signature detected in the data is much weaker, because of the low inclination, but would follow the velocity curve shown in the left-hand panel. The "barber's pole" pattern of travelling ripples lies wholly within the residual stellar profile, is wavelength independent, and probably originates in stellar surface features (see article by Andrew Collier Cameron). [ GIF | TIFF ] More information:
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