A Super-Earth Transiting a Naked-Eye Star
Author(s)Winn, Joshua Nathan; Matthews, Jaymie M.; Dawson, Rebekah I.; Fabrycky, Daniel C.; Holman, Matthew J.; Kallinger, Thomas; Kuschnig, Rainer; Sasselov, Dimitar; Dragomir, Diana; Guenther, David B.; Moffat, Anthony F.; Rowe, Jason F.; Rucinski, Slavek; Weiss, Werner W.; ... Show more Show less
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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+0.051 – 0.029 M ☉ and 0.943 ± 0.010 R ☉, the planet's mass, radius, and mean density are 8.63 ± 0.35 M ⊕, 2.00 ± 0.14 R ⊕, and 5.9(superscript +1.5) – 1.1 g cm(superscript –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.
DepartmentMassachusetts Institute of Technology. Department of Physics; MIT Kavli Institute for Astrophysics and Space Research
Astrophysical Journal. Letters
Winn, Joshua N. et al. “A SUPER-EARTH TRANSITING A NAKED-EYE STAR.” The Astrophysical Journal 737.1 (2011): L18.
Author's final manuscript