• DOI:10.1038/nature10684
• Corpus ID: 2614136

One or more bound planets per Milky Way star from microlensing observations

@article{Cassan2012OneOM,
  title={One or more bound planets per Milky Way star from microlensing observations},
  author={Arnaud Cassan and Daniel Kubas and Jean Philippe Beaulieu and Martin Dominik and Keith Horne and John G. Greenhill and Joachim Wambsganss and John W Menzies and A. Williams and U. G. J{\o}rgensen and Andrzej Udalski and David P. Bennett and Michael D. Albrow and Virginie Batista and St{\'e}phane Brillant and John A. R. Caldwell and Andrew A. Cole and Ch. Coutures and K. H. Cook and Stefan W. Dieters and D. Dominis Prester and Jadzia Donatowicz and P Fouqu{\'e} and K. M. Hill and N. Kains and Stephen R. Kane and Jean Baptiste Marquette and R. M. Martin and Karen Pollard and Kailash C. Sahu and Christian Vinter and D. M. Warren and B. Watson and Marta Zub and Takahiro Sumi and Michał K. Szymański and Marcin Kubiak and Radosław Poleski and Igor Soszyński and Krzysztof Ulaczyk and Grzegorz Pietrzyński and Łukasz Wyrzykowski},
  journal={Nature},
  year={2012},
  volume={481},
  pages={167-169}
}

• A. Cassan, D. Kubas, +39 authors Ł. Wyrzykowski
• Published 12 January 2012
• Physics, Geology
• Nature

Most known extrasolar planets (exoplanets) have been discovered using the radial velocity or transit methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17–30% (refs 4, 5) of solar-like stars host a planet. Gravitational microlensing, on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing. These planets are at least as numerous as the stars in the Milky Way. Here we report a statistical analysis of microlensing data (gathered in 2002–07) that reveals the fraction of bound planets 0.5–10 au (Sun–Earth distance) from their stars. We find that of stars host Jupiter-mass planets (0.3–10 MJ, where MJ = 318 M⊕ and M⊕ is Earth’s mass). Cool Neptunes (10–30 M⊕) and super-Earths (5–10 M⊕) are even more common: their respective abundances per star are and . We conclude that stars are orbited by planets as a rule, rather than the exception.