An extrasolar planetary system with three Neptune-mass planets

Abstract

Over the past two years, the search for low-mass extrasolar planets has led to the detection of seven so-called ‘hot Neptunes’ or ‘super-Earths’ around Sun-like stars. These planets have masses 5–20 times larger than the Earth and are mainly found on close-in orbits with periods of 2–15 days. Here we report a system of three Neptune-mass planets with periods of 8.67, 31.6 and 197 days, orbiting the nearby star HD 69830. This star was already known to show an infrared excess possibly caused by an asteroid belt within 1 au (the Sun–Earth distance). Simulations show that the system is in a dynamically stable configuration. Theoretical calculations favour a mainly rocky composition for both inner planets, while the outer planet probably has a significant gaseous envelope surrounding its rocky/icy core; the outer planet orbits within the habitable zone of this star.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Phase-folded radial velocity curves for the three planets.
Figure 2: Radial velocity curve as a function of time.
Figure 3: Dynamical study of the HD 69830 system.

References

  1. 1

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

    ADS  CAS  Article  Google Scholar 

  2. 2

    Udry, S., Fischer, D. A. & Queloz, D. in Protostars and Planets V (eds Reipurth, B., Jewitt, D. & Keil, K.) (Univ. Arizona Press, Tucson, in the press)

  3. 3

    Schneider, J. The Extrasolar Planets Encyclopaedia. http://exoplanet.eu (10 March 2006).

  4. 4

    Perryman, M. A. C. et al. The HIPPARCOS catalogue. Astron. Astrophys. 323, L49–L52 (1997)

    ADS  Google Scholar 

  5. 5

    Santos, N. C., Israelian, G. & Mayor, M. Spectroscopic [Fe/H] for 98 extra-solar planet-host stars. Exploring the probability of planet formation. Astron. Astrophys. 415, 1153–1166 (2004)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Schaller, G., Schaerer, D., Meynet, G. & Maeder, A. New grids of stellar models from 0.8 to 120 solar masses at Z = 0.020 and Z = 0.001. Astron. Astrophys. Suppl. Ser. 96, 269–331 (1992)

    ADS  Google Scholar 

  7. 7

    Girardi, L., Bressan, A., Bertelli, G. & Chiosi, C. Evolutionary tracks and isochrones for low- and intermediate-mass stars: From 0.15 to 7 Msun, and from Z = 0.0004 to 0.03. Astron. Astrophys. Suppl. Ser. 141, 371–383 (2000)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Beichman, C. A. et al. An excess due to small grains around the nearby K0 V star HD 69830: Asteroid or cometary debris? Astrophys. J. 626, 1061–1069 (2005)

    ADS  CAS  Article  Google Scholar 

  9. 9

    Mayor, M. et al. Setting new standards with HARPS. Messenger 114, 20–24 (2003)

    ADS  Google Scholar 

  10. 10

    Pepe, F. et al. The HARPS search for southern extra-solar planets. I. HD 330075 b: A new “hot Jupiter”. Astron. Astrophys. 423, 385–389 (2004)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Santos, N. C. et al. The HARPS survey for southern extra-solar planets. II. A 14 Earth-masses exoplanet around µ Arae. Astron. Astrophys. 426, L19–L23 (2004)

    ADS  Article  Google Scholar 

  12. 12

    Lovis, C. et al. The HARPS search for southern extra-solar planets. III. Three Saturn-mass planets around HD 93083, HD 101930 and HD 102117. Astron. Astrophys. 437, 1121–1126 (2005)

    ADS  Article  Google Scholar 

  13. 13

    Udry, S. et al. The HARPS search for southern extra-solar planets. V. A 14 Earth-masses planet orbiting HD 4308. Astron. Astrophys. 447, 361–367 (2006)

    ADS  Article  Google Scholar 

  14. 14

    Baranne, A. et al. ELODIE: A spectrograph for accurate radial velocity measurements. Astron. Astrophys. 119 (Suppl.), 373–390 (1996)

    ADS  Google Scholar 

  15. 15

    Bouchy, F., Bazot, M., Santos, N. C., Vauclair, S. & Sosnowska, D. Asteroseismology of the planet-hosting star µ Arae. I. The acoustic spectrum. Astron. Astrophys. 440, 609–614 (2005)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Noyes, R. W., Hartmann, L. W., Baliunas, S. L., Duncan, D. K. & Vaughan, A. H. Rotation, convection, and magnetic activity in lower main-sequence stars. Astrophys. J. 279, 763–777 (1984)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Santos, N. C. et al. The CORALIE survey for southern extra-solar planets. IX. A 1.3-day period brown dwarf disguised as a planet. Astron. Astrophys. 392, 215–229 (2002)

    ADS  CAS  Article  Google Scholar 

  18. 18

    Queloz, D. et al. No planet for HD 166435. Astron. Astrophys. 379, 279–287 (2001)

    ADS  CAS  Article  Google Scholar 

  19. 19

    Correia, A. C. M. et al. The CORALIE survey for southern extra-solar planets. XIII. A pair of planets around HD 202206 or a circumbinary planet? Astron. Astrophys. 440, 751–758 (2005)

    ADS  Article  Google Scholar 

  20. 20

    Laskar, J. Frequency analysis for multidimensional systems–global dynamics and diffusion. Physica D 67, 257–281 (1993)

    ADS  MathSciNet  Article  Google Scholar 

  21. 21

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

    ADS  Article  Google Scholar 

  22. 22

    Alibert, Y., Mordasini, C., Benz, W. & Winisdoerffer, C. Models of giant planet formation with migration and disc evolution. Astron. Astrophys. 434, 343–353 (2005)

    ADS  Article  Google Scholar 

  23. 23

    Ida, S. & Lin, D. N. C. Toward a deterministic model of planetary formation. I. A desert in the mass and semimajor axis distributions of extrasolar planets. Astrophys. J. 604, 388–413 (2004)

    ADS  Article  Google Scholar 

  24. 24

    Lecavelier des Etangs, A., Vidal-Madjar, A., McConnell, J. C. & Hébrard, G. Atmospheric escape from hot Jupiters. Astron. Astrophys. 418, L1–L4 (2004)

    ADS  Article  Google Scholar 

  25. 25

    Baraffe, I., Alibert, Y., Chabrier, G. & Benz, W. Birth and fate of hot-Neptune planets. Astron. Astrophys. (in the press); preprint at http://arXiv.org/astro-ph/0512091 (2005)

  26. 26

    Haisch, K. E., Lada, E. A. & Lada, C. J. Disk frequencies and lifetimes in young clusters. Astrophys. J. 553, L153–L156 (2001)

    ADS  CAS  Article  Google Scholar 

  27. 27

    Beckwith, S. V. W. & Sargent, A. I. Circumstellar disks and the search for neighbouring planetary systems. Nature 383, 139–144 (1996)

    ADS  CAS  Article  Google Scholar 

  28. 28

    Tanaka, H., Takeuchi, T. & Ward, W. R. Three-dimensional interaction between a planet and an isothermal gaseous disk. I. Corotation and Lindblad torques and planet migration. Astrophys. J. 565, 1257–1274 (2002)

    ADS  Article  Google Scholar 

  29. 29

    Alibert, Y., Mousis, O., Mordasini, C. & Benz, W. New Jupiter and Saturn formation models meet observations. Astrophys. J. 626, L57–L60 (2005)

    ADS  CAS  Article  Google Scholar 

  30. 30

    Kasting, J. F., Whitmire, D. P. & Reynolds, R. T. Habitable zones around main sequence stars. Icarus 101, 108–128 (1993)

    ADS  CAS  Article  Google Scholar 

Download references

Acknowledgements

The data presented here were obtained with the ESO 3.6-m telescope at La Silla Paranal Observatory, Chile. We thank O. Tamuz for the development of the genetic algorithm code, and J. Couetdic for his help in studying the stability of the asteroid belt. We thank the Swiss National Science Foundation (FNRS), the Centre National de la Recherche Scientifique (France) and the Fundação para Ciência e a Tecnologia (Portugal) for their continuous support.

Author information

Affiliations

Authors

Corresponding authors

Correspondence to Christophe Lovis or Michel Mayor.

Ethics declarations

Competing interests

Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Supplementary information

Supplementary Table 1

This table contains the 74 radial velocity measurements of the star HD 69830 that we have obtained with the HARPS instrument. The format is ASCII text with a tabulation as separation character. The first column contains the epoch of the measurements as Barycentric Julian Date (BJD) minus 2,400,000 (for clarity). The second column gives the radial velocity of the star in km s-1 relative to the Solar System barycenter. Finally, the third column gives the uncertainties on the measurements in km s-1. (TXT 2 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Lovis, C., Mayor, M., Pepe, F. et al. An extrasolar planetary system with three Neptune-mass planets. Nature 441, 305–309 (2006). https://doi.org/10.1038/nature04828

Download citation

Further reading

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

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