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Centro de Astrofísica da Universidade do Porto

An Earth-sized planet with an Earth-like density

F. Pepe, A. Collier Cameron, D. W. Latham, E. Molinari, S. Udry, A. S. Bonomo, L. A. Buchhave, D. Charbonneau, R. Cosentino, C. D. Dressing, X. Dumusque, P. Figueira, A. F. Martínez Fiorenzano, S. Gettel, H. Avet, R. D. Haywood, K. Horne, M. López-Morales, C. Lovis, L. Malavolta, M. Mayor, G. Micela, F. Motalebi, V. Nascimbeni, D. F. Phillips, G. Piotto, D. Pollacco, D. Queloz, K. Rice, D. Sasselov, D. Ségransan, A. Sozzetti, A. Szentgyorgyi, C. A. Watson

Recent analyses of data from the NASA Kepler spacecraft have established that planets with radii within 25 per cent of Earth’s (R) are commonplace throughout the Galaxy, orbiting at least 16.5 per cent of Sun-like stars. Because these studies were sensitive to the sizes of the planets but not their masses, the question remains whether these Earth-sized planets are indeed similar to the Earth in bulk composition. The smallest planets for which masses have been accurately determined are Kepler-10b (1.42R) and Kepler-36b (1.49R), which are both significantly larger than the Earth. Recently, the planet Kepler-78b was discovered and found to have a radius of only 1.16R. Here we report that the mass of this planet is 1.86 Earth masses. The resulting mean density of the planet is 5.57 g cm-3, which is similar to that of the Earth and implies a composition of iron and rock.

Volume 503, Page 377
November 2013

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Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

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