Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

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

Nature volume 481, pages 167–169 (2012)Cite this article

Subjects

Abstract

Most known extrasolar planets (exoplanets) have been discovered using the radial velocity1,2 or transit3 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 microlensing6,7,8,9, 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 microlensing10. These planets are at least as numerous as the stars in the Milky Way10. 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.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Get just this article for as long as you need it

$39.95

Learn more

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Survey-sensitivity diagram.
Figure 2: Cool-planet mass function.

References

  1. Mayor, M. & Queloz, D. A. Jupiter-mass companion to a solar-type star. Nature 378, 355–359 (1995)

    Article  ADS  CAS  Google Scholar 

  2. Marcy, G. W. & Butler, R. P. A planetary companion to 70 Virginis. Astrophys. J. 464, L147–L151 (1996)

    Article  ADS  Google Scholar 

  3. Charbonneau, D., Brown, T. M., Latham, D. W. & Mayor, M. Detection of planetary transits across a Sun-like star. Astrophys. J. 529, L45–L48 (2000)

    Article  ADS  CAS  Google Scholar 

  4. Howard, A. et al. Planet occurrence within 0.25 AU of Solar-type stars from Kepler. Astrophys. J. (submitted); preprint at http://arxiv.org/abs/1103.2541 (2011)

  5. Mayor, M. et al. The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets. Astron. Astrophys. (submitted); preprint at http://arxiv.org/abs/1109.2497 (2011)

  6. Mao, S. & Paczynski, B. Gravitational microlensing by double stars and planetary systems. Astrophys. J. 374, L37–L40 (1991)

    Article  ADS  Google Scholar 

  7. Gould, A. & Loeb, A. Discovering planetary systems through gravitational microlenses. Astrophys. J. 396, 104–114 (1992)

    Article  ADS  Google Scholar 

  8. Bennett, D. P. & Rhie, S. H. Detecting Earth-mass planets with gravitational microlensing. Astrophys. J. 472, 660–664 (1996)

    Article  ADS  Google Scholar 

  9. Wambsganss, J. Discovering Galactic planets by gravitational microlensing: magnification patterns and light curves. Mon. Not. R. Astron. Soc. 284, 172–188 (1997)

    Article  ADS  Google Scholar 

  10. Sumi, T. et al. Unbound or distant planetary mass population detected by gravitational microlensing. Nature 473, 349–352 (2011)

    Article  ADS  CAS  Google Scholar 

  11. Udalski, A. The Optical Gravitational Lensing Experiment. Real time data analysis systems in the OGLE-III survey. Acta Astronaut. 53, 291–305 (2003)

    Google Scholar 

  12. Bond, I. A. et al. Real-time difference imaging analysis of MOA Galactic bulge observations during 2000. Mon. Not. R. Astron. Soc. 327, 868–880 (2001)

    Article  ADS  Google Scholar 

  13. Albrow, M. et al. The 1995 pilot campaign of PLANET: searching for microlensing anomalies through precise, rapid, round-the-clock monitoring. Astrophys. J. 509, 687–702 (1998)

    Article  ADS  Google Scholar 

  14. Gould, A. et al. Microlens OGLE-2005-BLG-169 implies that cool Neptune-like planets are common. Astrophys. J. 644, L37–L40 (2006)

    Article  ADS  Google Scholar 

  15. Gaudi, B. S. et al. Discovery of a Jupiter/Saturn analog with gravitational microlensing. Science 319, 927–930 (2008)

    Article  ADS  CAS  Google Scholar 

  16. Udalski, A. et al. A Jovian-mass planet in microlensing event OGLE-2005-BLG-071. Astrophys. J. 628, L109–L112 (2005)

    Article  ADS  Google Scholar 

  17. Dong, S. et al. OGLE-2005-BLG-071Lb, the most massive M dwarf planetary companion? Astrophys. J. 695, 970–987 (2009)

    Article  ADS  Google Scholar 

  18. Gould, A. et al. Frequency of solar-like systems and of ice and gas giants beyond the snow line from high-magnification microlensing events in 2005–2008. Astrophys. J. 720, 1073–1089 (2010)

    Article  ADS  Google Scholar 

  19. Beaulieu, J.-P. et al. Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing. Nature 439, 437–440 (2006)

    Article  ADS  CAS  Google Scholar 

  20. Kubas, D. et al. Limits on additional planetary companions to OGLE 2005-BLG-390L. Astron. Astrophys. 483, 317–324 (2008)

    Article  ADS  Google Scholar 

  21. Gaudi, B. S. et al. Microlensing constraints on the frequency of Jupiter-mass companions: analysis of 5 years of PLANET photometry. Astrophys. J. 566, 463–499 (2002)

    Article  ADS  Google Scholar 

  22. Einstein, A. Lens-like action of a star by the deviation of light in the gravitational field. Science 84, 506–507 (1936)

    Article  ADS  CAS  Google Scholar 

  23. Dominik, M. Stochastic distributions of lens and source properties for observed galactic microlensing events. Mon. Not. R. Astron. Soc. 367, 669–692 (2006)

    Article  ADS  Google Scholar 

  24. Cassan, A. An alternative parameterisation for binary-lens caustic-crossing events. Astron. Astrophys. 491, 587–595 (2008)

    Article  ADS  Google Scholar 

  25. Sumi, T. et al. A cold Neptune-mass planet OGLE-2007-BLG-368Lb: cold Neptunes are common. Astrophys. J. 710, 1641–1653 (2010)

    Article  ADS  Google Scholar 

  26. Howard, A. W. et al. The occurrence and mass distribution of close-in super-Earths, Neptunes, and Jupiters. Science 330, 653–655 (2010)

    Article  ADS  CAS  Google Scholar 

  27. Cumming, A. et al. The Keck Planet Search: Detectability and the minimum mass and orbital period distribution of extrasolar planets. Publ. Astron. Soc. Pacif. 120, 531–554 (2008)

    Article  ADS  Google Scholar 

  28. Pollack, J. B. et al. Formation of the giant planets by concurrent accretion of solids and gas. Icarus 124, 62–85 (1996)

    Article  ADS  Google Scholar 

  29. Tsapras, Y. et al. Microlensing limits on numbers and orbits of extrasolar planets from the 1998–2000 OGLE events. Mon. Not. R. Astron. Soc. 343, 1131–1144 (2003)

    Article  ADS  Google Scholar 

  30. Snodgrass, C. et al. The abundance of Galactic planets from OGLE-III 2002 microlensing data. Mon. Not. R. Astron. Soc. 351, 967–975 (2004)

    Article  ADS  Google Scholar 

Download references

Acknowledgements

Support for the PLANET project was provided by the HOLMES grant from the French Agence Nationale de la Recherche (ANR), the French National Centre for Scientific Research (CNRS), NASA, the US National Science Foundation, the Lawrence Livermore National Laboratory/National Nuclear Security Administration/Department of Energy, the French National Programme of Planetology, the Program of International Cooperation in Science France–Australia, D. Warren, the German Research Foundation, the Instrument Center for Danish Astronomy and the Danish Natural Science Research Council. The OGLE collaboration is grateful for funding from the European Research Council Advanced Grants Program. K.Ho. acknowledges support from the Qatar National Research Fund. M.D. is a Royal Society University Research Fellow.

Author information

Authors and Affiliations

  1. Probing Lensing Anomalies Network (PLANET) Collaboration, Institut d’Astrophysique de Paris, Université Pierre & Marie Curie, UMR7095 UPMC–CNRS 98 bis boulevard Arago, 75014 Paris, France,

    A. Cassan, D. Kubas, J.-P. Beaulieu, M. Dominik, K. Horne, J. Greenhill, J. Wambsganss, J. Menzies, A. Williams, U. G. Jørgensen, D. P. Bennett, M. D. Albrow, V. Batista, S. Brillant, J. A. R. Caldwell, A. Cole, Ch. Coutures, K. H. Cook, S. Dieters, D. Dominis Prester, J. Donatowicz, P. Fouqué, K. Hill, N. Kains, S. Kane, J.-B. Marquette, R. Martin, K. R. Pollard, K. C. Sahu, C. Vinter, D. Warren, B. Watson & M. Zub

  2. Institut d’Astrophysique de Paris, Université Pierre & Marie Curie, UMR7095 UPMC–CNRS 98 bis boulevard Arago, 75014 Paris, France,

    A. Cassan, D. Kubas, J.-P. Beaulieu, V. Batista, Ch. Coutures & J.-B. Marquette

  3. Astronomischen Rechen-Instituts (ARI), Zentrum für Astronomie, Heidelberg University, Mönchhofstrasse 12–14, 69120 Heidelberg, Germany,

    A. Cassan, J. Wambsganss & M. Zub

  4. European Southern Observatory, Alonso de Cordoba 3107, Vitacura, Casilla 19001, Santiago, Chile,

    D. Kubas & S. Brillant

  5. Scottish Universities Physics Alliance (SUPA), University of St Andrews, School of Physics & Astronomy, North Haugh, St Andrews, KY16 9SS, UK,

    M. Dominik & K. Horne

  6. University of Tasmania, School of Maths and Physics, Private bag 37, GPO Hobart, Tasmania 7001, Australia,

    J. Greenhill, A. Cole, S. Dieters, K. Hill, D. Warren & B. Watson

  7. South African Astronomical Observatory, PO Box 9 Observatory 7935, South Africa,

    J. Menzies

  8. Perth Observatory, Walnut Road, Bickley, Perth 6076, Australia,

    A. Williams & R. Martin

  9. Niels Bohr Institute and Centre for Star and Planet Formation, Juliane Mariesvej 30, 2100 Copenhagen, Denmark,

    U. G. Jørgensen & C. Vinter

  10. Optical Gravitational Lensing Experiment (OGLE) Collaboration, Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland,

    A. Udalski, M. K. Szymański, M. Kubiak, R. Poleski, I. Soszynski, K. Ulaczyk, G. Pietrzyński & Ł. Wyrzykowski

  11. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland,

    A. Udalski, M. K. Szymański, M. Kubiak, R. Poleski, I. Soszynski, K. Ulaczyk, G. Pietrzyński & Ł. Wyrzykowski

  12. Physics Department, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, Indiana 46530, USA,

    D. P. Bennett

  13. Department of Physics & Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand,

    M. D. Albrow & K. R. Pollard

  14. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, 21218, Maryland, USA

    J. A. R. Caldwell & K. C. Sahu

  15. Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, PO Box 808, California 94550, USA,

    K. H. Cook

  16. Department of Physics, University of Rijeka, Omladinska 14, 51000 Rijeka, Croatia,

    D. Dominis Prester

  17. Department of Computing, Technical University of Vienna, Wiedner Hauptstrasse 10, 1040 Vienna, Austria,

    J. Donatowicz

  18. Laboratoire Astrophysique de Toulouse (LATT), Université de Toulouse, CNRS, 31400 Toulouse, France,

    P. Fouqué

  19. European Southern Observatory Headquarters, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany,

    N. Kains

  20. NASA Exoplanet Science Institute, Caltech, MS 100-22, 770 South Wilson Avenue, Pasadena, California 91125, USA,

    S. Kane

  21. Department of Earth and Space Science, Microlensing Observations in Astrophysics (MOA) Collaboration, Osaka University, Osaka 560-0043, Japan

    T. Sumi

  22. Department of Earth and Space Science, Osaka University, Osaka 560-0043, Japan

    T. Sumi

  23. Departamento de Fisica, Universidad de Concepción, Casilla 160-C, Concepción, Chile,

    G. Pietrzyński

  24. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK,

    Ł. Wyrzykowski

  25. Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK,

    J.-P. Beaulieu

Authors
  1. A. Cassan
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. D. Kubas
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. J.-P. Beaulieu
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. M. Dominik
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. K. Horne
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. J. Greenhill
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. J. Wambsganss
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. J. Menzies
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. A. Williams
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. U. G. Jørgensen
    View author publications

    You can also search for this author in PubMed Google Scholar

  11. A. Udalski
    View author publications

    You can also search for this author in PubMed Google Scholar

  12. D. P. Bennett
    View author publications

    You can also search for this author in PubMed Google Scholar

  13. M. D. Albrow
    View author publications

    You can also search for this author in PubMed Google Scholar

  14. V. Batista
    View author publications

    You can also search for this author in PubMed Google Scholar

  15. S. Brillant
    View author publications

    You can also search for this author in PubMed Google Scholar

  16. J. A. R. Caldwell
    View author publications

    You can also search for this author in PubMed Google Scholar

  17. A. Cole
    View author publications

    You can also search for this author in PubMed Google Scholar

  18. Ch. Coutures
    View author publications

    You can also search for this author in PubMed Google Scholar

  19. K. H. Cook
    View author publications

    You can also search for this author in PubMed Google Scholar

  20. S. Dieters
    View author publications

    You can also search for this author in PubMed Google Scholar

  21. D. Dominis Prester
    View author publications

    You can also search for this author in PubMed Google Scholar

  22. J. Donatowicz
    View author publications

    You can also search for this author in PubMed Google Scholar

  23. P. Fouqué
    View author publications

    You can also search for this author in PubMed Google Scholar

  24. K. Hill
    View author publications

    You can also search for this author in PubMed Google Scholar

  25. N. Kains
    View author publications

    You can also search for this author in PubMed Google Scholar

  26. S. Kane
    View author publications

    You can also search for this author in PubMed Google Scholar

  27. J.-B. Marquette
    View author publications

    You can also search for this author in PubMed Google Scholar

  28. R. Martin
    View author publications

    You can also search for this author in PubMed Google Scholar

  29. K. R. Pollard
    View author publications

    You can also search for this author in PubMed Google Scholar

  30. K. C. Sahu
    View author publications

    You can also search for this author in PubMed Google Scholar

  31. C. Vinter
    View author publications

    You can also search for this author in PubMed Google Scholar

  32. D. Warren
    View author publications

    You can also search for this author in PubMed Google Scholar

  33. B. Watson
    View author publications

    You can also search for this author in PubMed Google Scholar

  34. M. Zub
    View author publications

    You can also search for this author in PubMed Google Scholar

  35. T. Sumi
    View author publications

    You can also search for this author in PubMed Google Scholar

  36. M. K. Szymański
    View author publications

    You can also search for this author in PubMed Google Scholar

  37. M. Kubiak
    View author publications

    You can also search for this author in PubMed Google Scholar

  38. R. Poleski
    View author publications

    You can also search for this author in PubMed Google Scholar

  39. I. Soszynski
    View author publications

    You can also search for this author in PubMed Google Scholar

  40. K. Ulaczyk
    View author publications

    You can also search for this author in PubMed Google Scholar

  41. G. Pietrzyński
    View author publications

    You can also search for this author in PubMed Google Scholar

  42. Ł. Wyrzykowski
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

A.Ca. led the analysis and conducted the modelling and statistical analyses. A.Ca. and D.K. selected light curves from 2002–07 PLANET/OGLE microlensing seasons, analysed the data and wrote the Letter and Supplement. D.K. computed the magnification maps used for the detection-efficiency calculations. J.-P.B. and Ch.C. wrote the software for online data reduction at the telescopes. J.-P.B. led the PLANET collaboration, with M.D., J.G., J.M. and A.W.; P.F. and M.D.A. contributed to online and offline data reduction. M.D. contributed to the conversion of the detection efficiencies to physical parameter space and developed the PLANET real-time display system with A.W., M.D.A. and Ch.C.; K.Ho. and A.Ca. developed and tested the Bayesian formulation for fitting the two-parameter power-law mass function. J.G. edited the manuscript, conducted the main data cleaning and managed telescope operations at Mount Canopus (1 m) in Hobart. J.W. wrote the original magnification maps software, discussed the main implications and edited the manuscript. J.M., A.W. and U.G.J. respectively managed telescope operations in South Africa (South African Astronomical Observatory 1 m), Australia (Perth 0.61 m) and La Silla (Danish 1.54 m). A.U. led the OGLE campaign and provided the final OGLE photometry. D.P.B, V.B., S.B., J.A.R.C., A.Co., K.H.C., S.D., D.D.P., J.D., P.F., K.Hi., N.K., S.K., J.-B.M., R.M., K.R.P., K.C.S., C.V., D.W., B.W. and M.Z. were involved in the PLANET observing strategy and/or PLANET data acquisition, reduction, real-time analysis and/or commented on the manuscript. T.S. commented on the manuscript. M.K.S., M.K., R.P., I.S., K.U., G.P. and Ł.W. contributed to OGLE data.

Corresponding authors

Correspondence to A. Cassan or A. Cole.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

The file contains Supplementary Text and Data, Supplementary Figures 1-5 with legends, Supplementary Table 1 and additional references. (PDF 692 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Cassan, A., Kubas, D., Beaulieu, JP. et al. One or more bound planets per Milky Way star from microlensing observations. Nature 481, 167–169 (2012). https://doi.org/10.1038/nature10684

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature10684

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing