The planet orbiting \tau Boo at a separation of 0.046 AU could produce a reflected light flux as bright as 1 \times 10 ^ { -4 } relative to that of the star .
A spectrum of the system will contain a reflected light component which varies in amplitude and Doppler-shift as the planet orbits the star .
Assuming the secondary spectrum is primarily the reflected stellar spectrum , we can limit the relative reflected light flux to be less than 5 \times 10 ^ { -5 } .
This implies an upper limit of 0.3 for the planetary geometric albedo near 480 nm , assuming a planetary radius of 1.2 R _ { Jup } .
This albedo is significantly less than that of any of the giant planets of the solar system , and is not consistent with certain published theoretical predictions .