Winn, Joshua N × Matthews, Jaymie M Dawson, Rebekah I Fabrycky, Daniel Holman, Matthew J Kallinger, Thomas Kuschnig, Rainer Sasselov, Dimitar Dragomir, Diana Guenther, David B Moffat, Anthony F. J Rowe, Jason F Rucinski, Slavek Weiss, Werner W #
I O P Publishing Ltd.
The Astrophysical Journal. Letters vol:737 issue:1 pages:-
We have detected transits of the innermost planet "e" orbiting 55 Cnc (V = 6.0), based on two weeks of nearly continuous photometric monitoring with the MOST space telescope. The transits occur with the period (0.74 days) and phase that had been predicted by Dawson & Fabrycky, and with the expected duration and depth for the crossing of a Sun-like star by a hot super-Earth. Assuming the star's mass and radius to be 0.963(-0.029)(+0.051) M-circle dot and 0.943+/-0.010 R-circle dot, the planet's mass, radius, and mean density are 8.63+/-0.35 M-circle plus, 2.00+/-0.14 R-circle plus, and 5.9(-1.1)(+1.5) g cm(-3), respectively. The mean density is comparable to that of Earth, despite the greater mass and consequently greater compression of the interior of 55 Cnc e. This suggests a rock-iron composition supplemented by a significant mass of water, gas, or other light elements. Outside of transits, we detected a sinusoidal signal resembling the expected signal due to the changing illuminated phase of the planet, but with a full range (168 +/- 70 ppm) too large to be reflected light or thermal emission. This signal has no straightforward interpretation and should be checked with further observations. The host star of 55 Cnc e is brighter than that of any other known transiting planet, which will facilitate future investigations.