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

A. Cassan, D. Kubas, J. -P. Beaulieu, Martin Dominik, Keith Douglas Horne, J. Greenhill, J. Wambsganss, J. Menzies, A. Williams, U. G. Jorgensen, A. Udalski, D. P. Bennett, M. D. Albrow, V. Batista, S. Brillant, J. A. R. Caldwell, A. Cole, Ch. Coutures, K. H. Cook, S. DietersD. Dominis Prester, J. Donatowicz, P. Fouque, K. Hill, Noé Kains, S. Kane, J. -B. Marquette, R. Martin, K. R. Pollard, K. C. Sahu, C. Vinter, D. Warren, B. Watson, M. Zub, T. Sumi, M. K. Szymanski, M. Kubiak, R. Poleski, I. Soszynski, K. Ulaczyk, G. Pietrzynski, L. Wyrzykowski

Research output: Contribution to journalArticlepeer-review

375 Citations (Scopus)

Abstract

Most known extrasolar planets (exoplanets) have been discovered using the radial velocity(1,2) or transit(3) 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(6-9), 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(10). These planets are at least as numerous as the stars in the Milky Way(10). 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 17(-9)(+6)% of stars host Jupiter-mass planets (0.3-10M(J), where M-J = 318 M-circle plus and M-circle plus is Earth's mass). Cool Neptunes (10-30 M-circle plus) and super-Earths (5-10 M-circle plus) are even more common: their respective abundances per star are 52(-29)(+22)% and 62(-37)(+35)%. We conclude that stars are orbited by planets as a rule, rather than the exception.

Original languageEnglish
Pages (from-to)167-169
Number of pages3
JournalNature
Volume481
Issue number7380
DOIs
Publication statusPublished - 12 Jan 2012

Keywords

  • EXTRASOLAR PLANETS
  • GALACTIC PLANETS
  • MASS PLANET
  • SYSTEMS
  • EVENTS
  • COMPANION
  • DISCOVERY
  • FREQUENCY
  • NEPTUNES
  • COMMON

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