Doppler spectroscopy as a path to the detection of Earth-like planets


Doppler spectroscopy was the first technique used to reveal the existence of extrasolar planetary systems hosted by solar-type stars. Radial-velocity surveys led to the detection of a rich population of super-Earths and Neptune-type planets. The numerous detected systems revealed a remarkable diversity. Combining Doppler measurements with photometric observations of planets transiting their host stars further provides access to the planet bulk density, a first step towards comparative exoplanetology. The development of new high-precision spectrographs and space-based facilities will ultimately lead us to characterize rocky planets in the habitable zone of our close stellar neighbours.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Exoplanet discoveries as a function of time.
Figure 2: Rossiter–McLaughlin effect for probing the spin-orbit alignment of exoplanets.
Figure 3: Mass–density diagram for Neptunes and super-Earths.
Figure 4: Metallicity distribution of planet-hosting stars.


  1. 1

    Jeans, J. Problems of Cosmogony and Stellar Dynamics, p. 290 (Cambridge University Press, 1919).

  2. 2

    Strand, K. 61 Cygni as a triple system. Publ. Astron. Soc. Pacif. 55, 29–32 (1943).

  3. 3

    Reuyl, D. & Holmberg, E. On the existence of a third component in the system 70 ophiuchi. Astrophys. J. 97, 41 (1943).

  4. 4

    Dick, S. J. in Bioastronomy – The Search for Extraterrestrial Life (eds J. Heidmann & M.J. Klein) 356–363 (Springer, 1991).

  5. 5

    Belorizky, D. Le Soleil, étoile variable. L'Astronomie 52, 359–361 (1938).

  6. 6

    Struve, O. Proposal for a project of high-precision stellar radial velocity work. Observatory 72, 199–200 (1952).

  7. 7

    Campbell, B. & Walker, G. A. H. in Stellar Radial Velocities: IAU Colloquium 88 (eds Davis Philip, A.G. & Latham, D.) 5–18 (L. Davis, 1985).

  8. 8

    Walker, G. A. H. et al. A search for Jupiter-mass companions to nearby stars. Icarus 116, 359–375 (1995).

  9. 9

    Marcy, G. W. & Butler, R. P. in The Bottom of the Main Sequence and Beyond (ed. Tinney, C.) 98 (Springer, 1994).

  10. 10

    Latham, D. W., Stefanik, R. P., Mazeh, T., Mayor, M. & Burki, G. The unseen companion of HD114762 – a probable brown dwarf. Nature 339, 38–40 (1989).

  11. 11

    Mordasini, C., Alibert, Y., Benz, W., Klahr, H. & Henning, T. Extrasolar planet population synthesis. IV. Correlations with disk metallicity, mass, and lifetime. Astron. Astrophys. 541, A97–A119 (2012). Exoplanet population synthesis models, which try to reproduce ensemble properties of exoplanets from protoplanetary disk evolution.

  12. 12

    Santos, N. et al. The HARPS search for southern extrasolar planets. XXV. Results from a metal-poor sample. Astron. Astrophys. 526, A112–A128 (2011).

  13. 13

    Santos, N. et al. SWEET-Cat: a catalogue of parameters for stars with exoplanets. I. New atmospheric parameters and masses for 48 stars with planets. Astron. Astrophys. 556, A150 (2013).

  14. 14

    Campbell, B., Walker, G. A. & Yang, S. A search for substellar companions to solar-type stars. Astrophys. J. 331, 902–921 (1988).

  15. 15

    Marcy, G. W. & Butler, R. P. Precision radial velocities with an iodine absorption cell. Publ. Astron. Soc. Pacif. 104, 270–277 (1992).

  16. 16

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

  17. 17

    Mayor, M. & Queloz, D. A Jupiter-mass companion to a solar-type star. Nature 378, 355–359 (1995). This paper reports the discovery of 51 Peg b, the first confirmed exoplanet around a solar-type star.

  18. 18

    Boss, A. Proximity of Jupiter-like planets to low-mass stars. Science 267, 360–362 (1995).

  19. 19

    Lin, D. N. C., Bodenheimer, P. & Richardson, D. C. Orbital migration of the planetary companion of 51 Pegasi to its present location. Nature 380, 606–607 (1996). This was the first attempt at explaining the existence of hot Jupiters in terms of orbital migration within a protoplanetary disk.

  20. 20

    Goldreich, P. & Tremaine, S. Disk-satellite interactions. Astrophys. J. 241, 425–441 (1980).

  21. 21

    Lin, D. N. C. & Papaloizou, J. On the tidal interaction between protoplanets and the protoplanetary disk. III – orbital migration of protoplanets. Astrophys. J. 309, 846–857 (1986).

  22. 22

    Butler, R. P., Marcy, G. W., Williams, E., Hauser, A. & Shirts, P. Three new 51 Pegasi-type planets. Astrophys. J. 474, L115–L118 (1997). This article provided confirmation that 51 Peg b is not unique: hot Jupiters exist around many stars.

  23. 23

    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). This article reports the first detection of an exoplanetary transit.

  24. 24

    Henry, G. W., Marcy, G. W., Butler, R. P. & Vogt, S. S. A transiting 51 Peg-like planet. Astrophys. J. 529, L41–L44 (2000).

  25. 25

    Brown, T. M., Charbonneau, D., Gillilland, R. L., Noyes, R. W. & Burrows, A. Hubble space telescope time-series photometry of the transiting planet of HD 209458. Astrophys. J. 552, 699–709 (2001).

  26. 26

    Brogi, M. et al. Detection of molecular absorption in the dayside of exoplanet 51 Pegasi b. Astrophys. J. 767, 27–36 (2013).

  27. 27

    Butler, R. P. et al. Attaining Doppler precision of 3 m/s. Publ. Astron. Soc. Pacif. 108, 500–509 (1996).

  28. 28

    Cochran, W. D. & Hatzes, A. P. in Precise Stellar Radial Velocities IAU Colloquium 170 (eds Hearnshaw, J. B. & Scarfe, C. D.) 113 (Astron. Soc. Pacif., 1999).

  29. 29

    Queloz, D. et al. The CORALIE survey for southern extra-solar planets. I. A planet orbiting the star Gliese 86. Astron. Astrophys. 354, 99–102 (2000).

  30. 30

    Endl, M., Kürster, M. & Els, S. The planet search program at the ESO Coudé Echelle spectrometer. I. Data modeling technique and radial velocity precision tests. Astron. Astrophys. 362, 585–594 (2000).

  31. 31

    Tinney, C. G. et al. First results from the Anglo-Australian planet search: a brown dwarf candidate and a 51 Peg-like planet. Astrophys. J. 551, 507–511 (2001).

  32. 32

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

  33. 33

    Dumusque, X. et al. An Earth-mass planet orbiting α Cen B. Nature 491, 207–211 (2012). This article reports the discovery of an Earth-mass planet on a short-period orbit around α Cen B, our closest stellar neighbour.

  34. 34

    Udry, S. & Santos, N. C. Statistical properties of exoplanets. Annu. Rev. Astron. Astrophys. 45, 397–439 (2007).

  35. 35

    Mayor, M. et al. The HARPS search for southern extra-solar planets. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets. Preprint at: (2011)

  36. 36

    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).

  37. 37

    Wright, J. T. et al. The frequency of hot Jupiters orbiting nearby solar-type stars. Astrophys. J. 753, 160–164 (2012).

  38. 38

    Wright, J. T. et al. Ten new and updated multiplanet systems and a survey of exoplanetary Systems. Astrophys. J. 693, 1084–1099 (2009).

  39. 39

    Correia, A. C. M. et al. The HARPS search for southern extra-solar planets. XVI. HD 45364, a pair of planets in a 3:2 mean motion resonance. Astron. Astrophys. 496, 521–526 (2009).

  40. 40

    Correia, A. C. M. et al. The HARPS search for southern extra-solar planets. XIX. Characterization and dynamics of the GJ 876 planetary system. Astron. Astrophys. 511, A21 (2010).

  41. 41

    Chatterjee, S., Ford, E. B., Matsumura, S. & Rasio, F. A. Dynamical outcomes of planet-planet scattering. Astrophys. J. 686, 580–602 (2008).

  42. 42

    Ford, E. B. & Rasio, F. A. Origins of eccentric extrasolar planets: testing the planet-planet scattering model. Astrophys. J. 686, 621–636 (2008).

  43. 43

    Takeda, G. & Rasio, F. A. High orbital eccentricities of extrasolar planets induced by the Kozai mechanism. Astrophys. J. 627, 1001–1010 (2005).

  44. 44

    Pollacco, D. L. et al. The WASP project and the SuperWASP cameras. Publ. Astron. Soc. Pacif. 118, 1407–1418 (2006).

  45. 45

    Bakos, G. et al. Wide-field millimagnitude photometry with the HAT: a tool for extrasolar planet detection. Publ. Astron. Soc. Pacif. 116, 266–277 (2004).

  46. 46

    Bodenheimer, P., Lin, D. N. C. & Mardling, R. A. On the tidal inflation of short-period extrasolar planets. Astrophys. J. 548, 466–472 (2001).

  47. 47

    Guillot, T. & Showman, A. P. Evolution of 51 Pegasus b-like planets. Astron. Astrophys. 385, 156–165 (2002).

  48. 48

    Burrows, A., Hubeny, I., Budaj, J. & Hubbard, W. B. Possible solutions to the radius anomalies of transiting giant planets. Astrophys. J. 661, 502–514 (2007).

  49. 49

    Chabrier, G. & Baraffe, I. Heat transport in giant (Exo)planets: a new perspective. Astrophys. J. 661, L81–L84 (2007).

  50. 50

    Batygin, K. & Stevenson, D. J. Inflating hot Jupiters with ohmic dissipation. Astrophys. J. 714, L238–L243 (2010).

  51. 51

    Triaud, A. H. M. J. et al. Spin-orbit angle measurements for six southern transiting planets. New insights into the dynamical origins of hot Jupiters. Astron. Astrophys. 524, A25 (2010).

  52. 52

    Winn, J. N., Fabrycky, D., Albrecht, S. & Johnson, J. A. Hot stars with hot Jupiters have high obliquities. Astrophys. J. 718, L145–L149 (2010).

  53. 53

    Rasio, F. A. & Ford, E. B. Dynamical instabilities and the formation of extrasolar planetary systems. Science 274, 954–956 (1996).

  54. 54

    Holman, M., Touma, J. & Tremaine, S. Chaotic variations in the eccentricity of the planet orbiting 16 Cygni B. Nature 386, 254–256 (1997).

  55. 55

    Crida, A. & Batygin, K. Spin-orbit angle distribution and the origin of (mis)aligned hot Jupiters. Astron. Astrophys. (in the press).

  56. 56

    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).

  57. 57

    Butler, R. P. et al. A Neptune-mass planet orbiting the nearby M dwarf GJ 436. Astrophys. J. 617, 580–588 (2004).

  58. 58

    McArthur, B. E. et al. Detection of a Neptune-mass planet in the ρ-1 Cancri system using the Hobby-Eberly telescope. Astrophys. J. 614, L81–L84 (2004).

  59. 59

    Lovis, C. et al. An extrasolar planetary system with three Neptune-mass planets. Nature 441, 305–309 (2006).

  60. 60

    Lovis, C. et al. Towards the characterization of the hot Neptune/super-Earth population around nearby bright stars. Proc. IAU Symp. 253, 502–505 (2009).

  61. 61

    Borucki, W. J. et al. Characteristics of planetary candidates observed by Kepler II. Analysis of the first four months of data. Astrophys. J. 736, 19 (2011).

  62. 62

    Bonfils, X. et al. The HARPS search for southern extra-solar planets. XXXI. The M-dwarf sample. Astron. Astrophys. 549, A109 (2013).

  63. 63

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

  64. 64

    Terquem, C. & Papaloizou, J. C. B. Migration and the formation of systems of hot super-Earths and Neptunes. Astrophys. J. 654, 1110–1120 (2007).

  65. 65

    Chiang, E. & Laughlin, G. The minimum-mass extrasolar nebula: in situ formation of close-in super-Earths. Mon. Not. R. Astron. Soc. 431, 3444–3455 (2013).

  66. 66

    Dawson, R. I. & Fabrycky, D. C. Radial velocity planets de-aliased: a new, short period for super-Earth 55 Cnc e. Astrophys. J. 722, 937–953 (2010).

  67. 67

    Demory, B.-O. et al. Detection of a transit of the super-Earth 55 Cancri e with warm Spitzer. Astron. Astrophys. 533, A114 (2011).

  68. 68

    Winn, J. N. et al. A super-Earth transiting a naked-eye star. Astrophys. J. 737, L18 (2011).

  69. 69

    Howard, A. W. et al. The NASA-UC Eta-Earth program. III. A super-Earth orbiting HD 97658 and a Neptune-mass planet orbiting Gl 785. Astrophys. J. 730, 10 (2011).

  70. 70

    Dragomir, D. et al. MOST detects transits of HD 97658b, a warm, likely volatile-rich super-Earth. Astrophys. J. 772, L2 (2013).

  71. 71

    Charbonneau, D. et al. A super-Earth transiting a nearby low-mass star. Nature 462, 891–894 (2009).

  72. 72

    Bonfils, X. et al. A hot Uranus transiting the nearby M dwarf GJ 3470. Detected with HARPS velocimetry. Captured in transit with TRAPPIST photometry. Astron. Astrophys. 546, A27 (2012).

  73. 73

    Gillon, M. et al. Detection of transits of the nearby hot Neptune GJ 436 b. Astron. Astrophys. 472, L13–L16 (2007).

  74. 74

    Bakos, G. A. et al. HAT-P-11b: A super-Neptune planet transiting a bright K star in the Kepler field. Astrophys. J. 710, 1724–1745 (2010).

  75. 75

    Marcy, G. W. et al. Masses, radii, and orbits of small Kepler planets: the transition from gaseous to rocky planets. Astrophys. J. 210, 20 (2014).

  76. 76

    Pepe, F. et al. The HARPS search for Earth-like planets in the habitable zone. I. Very low-mass planets around HD 20794, HD 85512, and HD 192310. Astron. Astrophys. 534, A58–A73 (2011). This paper reports the detection of several super-Earths with sub-metre per second Doppler signals, including one close to the habitable zone of a K dwarf.

  77. 77

    Selsis, F. et al. Habitable planets around the star Gliese 581? Astron. Astrophys. 476, 1373–1387 (2007).

  78. 78

    Delfosse, X. et al. The HARPS search for southern extra-solar planets. XXXIII. Super-Earths around the M-dwarf neighbors Gl 433 and Gl 667C. Astron. Astrophys. 553, A8 (2013).

  79. 79

    Tuomi, M. et al. Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307. Astron. Astrophys. 549, A48 (2013).

  80. 80

    Kopparapu, R. K. et al. Habitable zones around main-sequence stars: new estimates. Astrophys. J. 765, 131 (2013).

  81. 81

    Dumusque, X., Santos, N. C., Udry, S., Lovis, C. & Bonfils X. Planetary detection limits taking into account stellar noise. II. Effect of stellar spot groups on radial-velocities. Astron. Astrophys. 527, A82 (2011).

  82. 82

    Dumusque, X. et al. The HARPS search for southern extra-solar planets. XXX. Planetary systems around stars with solar-like magnetic cycles and short-term activity variation. Astron. Astrophys. 535, A55 (2011).

  83. 83

    Meunier, N. & Lagrange, A.-M. Using the Sun to estimate Earth-like planets detection capabilities. IV. Correcting for the convective component. Astron. Astrophys. 551, A101 (2013).

  84. 84

    Aigrain, S., Pont, F. & Zucker, S. A simple method to estimate radial velocity variations due to stellar activity using photometry. Mon. Not. R. Astron. Soc. 419, 3147–3158 (2012).

  85. 85

    Boisse, I., Bonfils, X. & Santos, N. C. SOAP. A tool for the fast computation of photometry and radial velocity induced by stellar spots. Astron. Astrophys. 545, A109 (2012).

  86. 86

    Torres, G. et al. Improved parameters for extrasolar transiting planets. Astrophys. J. 677, 1324–1342 (2008).

  87. 87

    Guillot, T. et al. A correlation between the heavy element content of transiting extrasolar planets and the metallicity of their parent star. Astron. Astrophys. 453, L21–L24 (2006).

  88. 88

    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). A large-scale study of the correlation between giant-planet occurrence and the metallicity of the host star.

  89. 89

    Fischer, D. A. & Valenti, J. The planet-metallicity correlation. Astrophys. J. 622, 1102–1117 (2005).

  90. 90

    Sousa, S. G. et al. Spectroscopic stellar parameters for 582 FGK stars in the HARPS volume-limited sample. Revising the metallicity-planet correlation. Astron. Astrophys. 533, A141 (2011)

  91. 91

    Buchhave, L. A. An abundance of small exoplanets around stars with a wide range of metallicities. Nature 486, 375–377 (2012).

  92. 92

    Adibekyan, V. Zh. et al. Overabundance of α-elements in exoplanet-hosting stars. Astron. Astrophys. 543, A89 (2012)

  93. 93

    Israelian, G. et al. Enhanced lithium depletion in Sun-like stars with orbiting planets. Nature 462, 189–191 (2009).

  94. 94

    Baumann, P. et al. Lithium depletion in solar-like stars: no planet connection. Astron. Astrophys. 519, A87 (2010).

  95. 95

    Israelian, G. et al. Evidence for planet engulfment by the star HD82943. Nature 411, 163–166 (2001).

  96. 96

    Reddy, B. et al. A search for 6Li in stars with planets. Mon. Not. R. Astron. Soc. 335, 1005–1016 (2002).

  97. 97

    Ramírez, I. et al. A possible signature of terrestrial planet formation in the chemical composition of solar analogs. Astron. Astrophys. 521, A33 (2010).

  98. 98

    González Hernández, J. I. et al. Searching for the signatures of terrestrial planets in solar analogs. Astrophys. J. 720, 1592–1602 (2010).

  99. 99

    Dawson, R. & Murray-Clay, R. A. Giant planets orbiting metal-rich stars show signatures of planet-planet interactions. Astrophys. J. 767, L24 (2013).

  100. 100

    Adibekyan, V. Zh. et al. Orbital and physical properties of planets and their hosts: new insights on planet formation and evolution. Astron. Astrophys. 560, A51 (2013).

  101. 101

    Butler, R. P. et al. Evidence for multiple companions to υ Andromedae. Astrophys. J. 526, 916–927 (1999).

  102. 102

    Mazeh, T. et al. The spectroscopic orbit of the planetary companion transiting HD 209458. Astrophys. J. 532, L55–L58 (2000).

  103. 103

    Naef, D. et al. HD 80606 b, a planet on an extremely elongated orbit. Astron. Astrophys. 375, L27–L30 (2001).

  104. 104

    Moutou, C. et al. Photometric and spectroscopic detection of the primary transit of the 111-day-period planet HD 80 606 b. Astron. Astrophys. 498, L5–L8 (2009).

  105. 105

    Pepe, F. et al. The HARPS search for southern extra-solar planets. VIII. μ Arae, a system with four planets. Astron. Astrophys. 462, 769–776 (2007).

  106. 106

    Fischer, D. A. et al. Five planets orbiting 55 Cancri. Astrophys. J. 675, 790–801 (2008).

  107. 107

    Bouchy, F. et al. ELODIE metallicity-biased search for transiting hot Jupiters. II. A very hot Jupiter transiting the bright K star HD 189733. Astron. Astrophys. 444, L15–L19 (2005).

  108. 108

    Sato, B. et al. The N2K Consortium. II. A transiting hot Saturn around HD 149026 with a large dense core. Astrophys. J. 633, 465–473 (2005).

  109. 109

    Udry, S. et al. The HARPS search for southern extra-solar planets. XI. Super-Earths (5 and 8 ME) in a 3-planet system. Astron. Astrophys. 469, L43–L47 (2007).

  110. 110

    Mayor, M. et al. The HARPS search for southern extra-solar planets. XVIII. An Earth-mass planet in the GJ 581 planetary system. Astron. Astrophys. 507, 487–494 (2009).

  111. 111

    Hébrard, G. et al. Misaligned spin-orbit in the XO-3 planetary system? Astron. Astrophys. 488, 763–770 (2008).

  112. 112

    Mayor, M. et al. The HARPS search for southern extra-solar planets. XIII. A planetary system with 3 super-Earths (4.2, 6.9, and 9.2 ME). Astron. Astrophys. 493, 639–644 (2009).

  113. 113

    Rivera, E. J. et al. The Lick-Carnegie exoplanet survey: a Uranus-mass fourth planet for GJ 876 in an extrasolar Laplace configuration. Astrophys. J. 719, 890–899 (2010).

  114. 114

    Queloz, D. et al. WASP-8b: a retrograde transiting planet in a multiple system. Astron. Astrophys. 517, L1 (2010).

  115. 115

    Lovis, C. et al. The HARPS search for southern extra-solar planets. XXVIII. Up to seven planets orbiting HD 10180: probing the architecture of low-mass planetary systems. Astron. Astrophys. 528, A112 (2011). This article reports the discovery of a densely populated system with up to seven planets and the study of its dynamical architecture.

  116. 116

    Triaud, A. H. M. J. et al. The Rossiter-McLaughlin effect of CoRoT-3b and HD 189733b. Astron. Astrophys. 506, 377–384 (2009).

  117. 117

    Zeng, L. & Sasselov, D. A detailed model grid for solid planets from 0.1 through 100 Earth masses. Publ. Astron. Soc. Pacif. 125, 227–239 (2013).

Download references


We thank A. Triaud for his help in preparing Fig. 2. N.C.S. was supported by Fundação para a Ciência e a Tecnologia (FCT, Portugal) through the Investigador FCT contract reference IF/00169/2012 and POPH/FSE (EC) by FEDER funding through the program Programa Operacional de Factores de Competitividade-COMPETE. N.C.S. further acknowledges the support from the European Research Council/European Community under FP7 through Starting Grant agreement number 239953. M.M and C.L. acknowledge the support of the Swiss National Science Foundation.

Author information

Correspondence to Michel Mayor.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Additional information

Reprints and permissions information is available at

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Mayor, M., Lovis, C. & Santos, N. Doppler spectroscopy as a path to the detection of Earth-like planets. Nature 513, 328–335 (2014).

Download citation

Further reading


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.