Detecting and Characterizing Exomoons and Exorings

Living reference work entry


Since the discovery of a planet transiting its host star in the year 2000, thousands of additional exoplanets and exoplanet candidates have been detected, mostly by NASA’s Kepler space telescope. Some of them are almost as small as the Earth’s moon. As the solar system is teeming with moons, more than a hundred of which are in orbit around the eight local planets, and with all of the local giant planets showing complex ring systems, astronomers have naturally started to search for moons and rings around exoplanets in the past few years. We here discuss the principles of the observational methods that have been proposed to find moons and rings beyond the solar system, and we review the first searches. Though no exomoon or exoring has been unequivocally validated so far, theoretical and technological requirements are now on the verge of being mature for such discoveries.


  1. Agnor CB, Hamilton DP (2006) Neptune’s capture of its moon Triton in a binary-planet gravitational encounter. Nature 441:192–194. doi:10.1038/nature04792 ADSCrossRefGoogle Scholar
  2. Agol E, Jansen T, Lacy B, Robinson T, Meadows V (2015) The center of light: spectroastrometric detection of exomoons. ApJ 812:5. doi:10.1088/0004-637X/812/1/5, 1509.01615
  3. Auvergne M, Bodin P, Boisnard L et al (2009) The CoRoT satellite in flight: description and performance. A&A 506:411–424. doi:10.1051/0004-6361/200810860, 0901.2206
  4. Awiphan S, Kerins E (2013) The detectability of habitable exomoons with Kepler. MNRAS 432:2549–2561. doi:10.1093/mnras/stt614, 1304.2925
  5. Barnes JW, Fortney JJ (2004) Transit detectability of ring systems around extrasolar giant planets. ApJ 616:1193–1203. doi:10.1086/425067, astro-ph/0409506
  6. Ben-Jaffel L, Ballester GE (2014) Transit of Exomoon plasma tori: new diagnosis. ApJ 785:L30. doi:10.1088/2041-8205/785/2/L30, 1404.1084
  7. Bennett DP, Batista V, Bond IA et al (2014) MOA-2011-BLG-262Lb: a sub-earth-mass moon orbiting a gas giant primary or a high velocity planetary system in the galactic bulge. ApJ 785:155. doi:10.1088/0004-637X/785/2/155, 1312.3951
  8. Borucki WJ, Koch D, Basri G et al (2010) Kepler planet-detection mission: introduction and first results. Science 327:977. doi:10.1126/science.1185402 ADSCrossRefGoogle Scholar
  9. Braga-Ribas F, Sicardy B, Ortiz JL et al (2014) A ring system detected around the Centaur (10199) Chariklo. Nature 508:72–75. doi:10.1038/nature13155, 1409.7259
  10. Brown TM, Charbonneau D, Gilliland RL, Noyes RW, Burrows A (2001) Hubble space telescope time-series photometry of the transiting planet of HD 209458. ApJ 552:699–709. doi:10.1086/320580, astro-ph/0101336
  11. Cabrera J, Schneider J (2007) Detecting companions to extrasolar planets using mutual events. A&A 464:1133–1138. doi:10.1051/0004-6361:20066111, astro-ph/0703609
  12. Cameron AGW, Ward WR (1976) The origin of the Moon. In: Lunar and planetary science conference, Houston, vol 7Google Scholar
  13. Canup RM (2005) A giant impact origin of Pluto-Charon. Science 307:546–550. doi:10.1126/science.1106818 ADSCrossRefGoogle Scholar
  14. Canup RM, Ward WR (2002) Formation of the Galilean satellites: conditions of accretion. AJ 124:3404–3423. doi:10.1086/344684 ADSCrossRefGoogle Scholar
  15. Charbonneau D, Winn JN, Latham DW et al (2006) Transit photometry of the core-dominated planet HD 149026b. ApJ 636:445–452. doi:10.1086/497959, astro-ph/0508051
  16. Crida A, Charnoz S (2012) Formation of regular satellites from ancient massive rings in the solar system. Science 338:1196. doi:10.1126/science.1226477, 1301.3808
  17. de Wit J, Wakeford HR, Gillon M et al (2016) A combined transmission spectrum of the Earth-sized exoplanets TRAPPIST-1 b and c. Nature 537:69–72. doi:10.1038/nature18641, 1606.01103
  18. Deienno R, Yokoyama T, Nogueira EC, Callegari N, Santos MT (2011) Effects of the planetary migration on some primordial satellites of the outer planets. I. Uranus’ case. A&A 536:A57. doi:10.1051/0004-6361/201014862 Google Scholar
  19. Deienno R, Nesvorný D, Vokrouhlický D, Yokoyama T (2014) Orbital perturbations of the Galilean satellites during planetary encounters. AJ 148:25. doi:10.1088/0004-6256/148/2/25, 1405.1880
  20. Domingos RC, Winter OC, Yokoyama T (2006) Stable satellites around extrasolar giant planets. MNRAS 373:1227–1234. doi:10.1111/j.1365-2966.2006.11104.x ADSCrossRefGoogle Scholar
  21. Han C, Han W (2002) On the feasibility of detecting satellites of extrasolar planets via microlensing. ApJ 580:490–493. doi:10.1086/343082, astro-ph/0207372
  22. Heising MZ, Marcy GW, Schlichting HE (2015) A search for ringed exoplanets using Kepler photometry. ApJ 814:81. doi:10.1088/0004-637X/814/1/81, 1511.01083
  23. Heller R (2014) Detecting extrasolar Moons akin to solar system satellites with an orbital sampling effect. ApJ 787:14. doi:10.1088/0004-637X/787/1/14, 1403.5839
  24. Heller R (2016) Transits of extrasolar moons around luminous giant planets. A&A 588:A34. doi:10.1051/0004-6361/201527496, 1603.00174
  25. Heller R, Albrecht S (2014) How to determine an exomoon’s sense of orbital motion. ApJ 796:L1. doi:10.1088/2041-8205/796/1/L1, 1409.7245
  26. Heller R, Marleau GD, Pudritz RE (2015) The formation of the Galilean moons and Titan in the Grand Tack scenario. A&A 579:L4. doi:10.1051/0004-6361/201526348, 1506.01024
  27. Heller R, Hippke M, Jackson B (2016a) Modeling the orbital sampling effect of extrasolar moons. ApJ 820:88. doi:10.3847/0004-637X/820/2/88, 1603.07112
  28. Heller R, Hippke M, Placek B, Angerhausen D, Agol E (2016b) Predictable patterns in planetary transit timing variations and transit duration variations due to exomoons. A&A 591:A67. doi:10.1051/0004-6361/201628573, 1604.05094
  29. Hippke M (2015) On the detection of exomoons: a search in Kepler data for the orbital sampling effect and the scatter peak. ApJ 806:51. doi:10.1088/0004-637X/806/1/51, 1502.05033
  30. Jacobson SA, Morbidelli A (2014) Lunar and terrestrial planet formation in the grand tack scenario. Philos Trans R Soc Lond Ser A 372:0174. doi:10.1098/rsta.2013.0174, 1406.2697
  31. Kenworthy MA, Mamajek EE (2015) Modeling giant extrasolar ring systems in eclipse and the case of J1407b: sculpting by exomoons? ApJ 800:126. doi:10.1088/0004-637X/800/2/126, 1501.05652
  32. Kipping DM (2009a) Transit timing effects due to an exomoon. MNRAS 392:181–189. doi:10.1111/j.1365-2966.2008.13999.x, 0810.2243
  33. Kipping DM (2009b) Transit timing effects due to an exomoon – II. MNRAS 396:1797–1804. doi:10.1111/j.1365-2966.2009.14869.x, 0904.2565
  34. Kipping DM (2011) LUNA: an algorithm for generating dynamic planet-moon transits. MNRAS 416:689–709. doi:10.1111/j.1365-2966.2011.19086.x, 1105.3499
  35. Kipping DM, Fossey SJ, Campanella G (2009) On the detectability of habitable exomoons with Kepler-class photometry. MNRAS 400:398–405. doi:10.1111/j.1365-2966.2009.15472.x, 0907.3909
  36. Kipping DM, Bakos GÁ, Buchhave L, Nesvorný D, Schmitt A (2012) The hunt for exomoons with Kepler (HEK). I. Description of a new observational project. ApJ 750:115. doi:10.1088/0004-637X/750/2/115, 1201.0752
  37. Kipping DM, Schmitt AR, Huang X et al (2015) The hunt for exomoons with Kepler (HEK): V. A survey of 41 planetary candidates for exomoons. ApJ 813:14. doi:10.1088/0004-637X/813/1/14, 1503.05555
  38. Levison HF, Dones L, Chapman CR et al (2001) Could the lunar “Late Heavy Bombardment” have been triggered by the formation of Uranus and Neptune? Icarus 151:286–306. doi:10.1006/icar.2001.6608 ADSCrossRefGoogle Scholar
  39. Lewis KM, Sackett PD, Mardling RA (2008) Possibility of detecting Moons of pulsar planets through time-of-arrival analysis. ApJ 685:L153–L156. doi:10.1086/592743, 0805.4263
  40. Lewis KM, Ochiai H, Nagasawa M, Ida S (2015) Extrasolar binary planets II: detectability by transit observations. ApJ 805:27. doi:10.1088/0004-637X/805/1/27, 1504.06365
  41. Liebig C, Wambsganss J (2010) Detectability of extrasolar moons as gravitational microlenses. Astron Astrophys 520:A68, 13 ppADSCrossRefMATHGoogle Scholar
  42. Maciejewski G, Dimitrov D, Neuhäuser R et al (2010) Transit timing variation in exoplanet WASP-3b. MNRAS 407:2625–2631. doi:10.1111/j.1365-2966.2010.17099.x, 1006.1348
  43. Mamajek EE, Quillen AC, Pecaut MJ et al (2012) Planetary construction zones in occultation: discovery of an extrasolar ring system transiting a young sun-like star and future prospects for detecting eclipses by circumsecondary and circumplanetary disks. AJ 143:72. doi:10.1088/0004-6256/143/3/72, 1108.4070
  44. Marois C, Macintosh B, Barman T et al (2008) Direct imaging of multiple planets orbiting the star HR 8799. Science 322:1348. doi:10.1126/science.1166585, 0811.2606
  45. Montalto M, Gregorio J, Boué G et al (2012) A new analysis of the WASP-3 system: no evidence for an additional companion. Mon Not R Astron Soc 427(4):2757–2771. doi:10.1111/j.1365-2966.2012.21926.x,,
  46. Morbidelli A, Tsiganis K, Batygin K, Crida A, Gomes R (2012) Explaining why the uranian satellites have equatorial prograde orbits despite the large planetary obliquity. Icarus 219:737–740. doi:10.1016/j.icarus.2012.03.025, 1208.4685
  47. Moskovitz NA, Gaidos E, Williams DM (2009) The effect of lunarlike satellites on the orbital infrared light curves of Earth-analog planets. Astrobiology 9:269–277. doi:10.1089/ast.2007.0209, 0810.2069
  48. Noyola JP, Satyal S, Musielak ZE (2014) Detection of exomoons through observation of radio emissions. ApJ 791:25. doi:10.1088/0004-637X/791/1/25, 1308.4184
  49. Noyola JP, Satyal S, Musielak ZE (2016) On the radio detection of multiple-exomoon systems due to plasma torus sharing. ApJ 821:97. doi:10.3847/0004-637X/821/2/97, 1603.01862
  50. Ohta Y, Taruya A, Suto Y (2009) Predicting photometric and spectroscopic signatures of rings around transiting extrasolar planets. ApJ 690:1–12. doi:10.1088/0004-637X/690/1/1, astro-ph/0611466
  51. Pál A (2012) Light-curve modelling for mutual transits. MNRAS 420:1630–1635. doi:10.1111/j.1365-2966.2011.20151.x, 1111.1741
  52. Peters MA, Turner EL (2013) On the direct imaging of tidally heated exomoons. ApJ 769:98. doi:10.1088/0004-637X/769/2/98, 1209.4418
  53. Pollack JB, Reynolds RT (1974) Implications of Jupiter’s early contraction history for the composition of the galilean satellites. Icarus 21:248–253. doi:10.1016/0019-1035(74)90040-2 ADSCrossRefGoogle Scholar
  54. Pont F, Gilliland RL, Moutou C et al (2007) Hubble space telescope time-series photometry of the planetary transit of HD 189733: no Moon, no rings, starspots. A&A 476:1347–1355. doi:10.1051/0004-6361:20078269, 0707.1940
  55. Rauer H, Catala C, Aerts C et al (2014) The PLATO 2.0 mission. Exp Astron 38:249–330. doi:10.1007/s10686-014-9383-4, 1310.0696
  56. Robinson TD (2011) Modeling the infrared spectrum of the earth-Moon system: implications for the detection and characterization of Earthlike extrasolar planets and their Moonlike companions. ApJ 741:51. doi:10.1088/0004-637X/741/1/51, 1110.3744
  57. Rosenblatt P, Charnoz S, Dunseath KM et al (2016) Accretion of phobos and Deimos in an extended debris disc stirred by transient moons. Nat Geosci 9(8):581–583. ADSCrossRefGoogle Scholar
  58. Rufu R, Aharonson O, Perets HB (2017) A multiple-impact origin for the moon. Nature Geosci. Advance online publication. Google Scholar
  59. Samsing J (2015) Extracting periodic transit signals from noisy light curves using fourier series. ApJ 807:65. doi:10.1088/0004-637X/807/1/65, 1503.03504
  60. Santos NC, Martins JHC, Boué G et al (2015) Detecting ring systems around exoplanets using high resolution spectroscopy: the case of 51 Pegasi b. A&A 583:A50. doi:10.1051/0004-6361/201526673, 1509.00723
  61. Sartoretti P, Schneider J (1999) On the detection of satellites of extrasolar planets with the method of transits. A&AS 134:553–560. doi:10.1051/aas:1999148 ADSCrossRefGoogle Scholar
  62. Sato M, Asada H (2009) Effects of mutual transits by extrasolar planet-companion systems on light curves. PASJ 61:L29. 0906.2590Google Scholar
  63. Sengupta S, Marley MS (2016) Detecting exomoons around self-luminous giant exoplanets through polarization. ApJ 824:76. doi:10.3847/0004-637X/824/2/76, 1604.04773
  64. Simon A, Szatmáry K, Szabó GM (2007) Determination of the size, mass, and density of “exomoons” from photometric transit timing variations. A&A 470:727–731. doi:10.1051/0004-6361:20066560, 0705.1046
  65. Simon AE, Szabó GM, Szatmáry K, Kiss LL (2010) Methods for exomoon characterization: combining transit photometry and the Rossiter-McLaughlin effect. MNRAS 406:2038–2046. doi:10.1111/j.1365-2966.2010.16818.x ADSGoogle Scholar
  66. Simon AE, Szabó GM, Kiss LL, Szatmáry K (2012) Signals of exomoons in averaged light curves of exoplanets. MNRAS 419:164–171. doi:10.1111/j.1365-2966.2011.19682.x, 1108.4557
  67. Simon A, Szabó G, Kiss L, Fortier A, Benz W (2015) CHEOPS performance for exomoons: the detectability of exomoons by using optimal decision algorithm. PASP 127:1084–1095. doi:10.1086/683392, 1508.00321
  68. Skowron J, Udalski A, Szymański MK et al (2014) New method to measure proper motions of microlensed sources: application to candidate free-floating-planet event MOA-2011-BLG-262. ApJ 785:156. doi:10.1088/0004-637X/785/2/156, 1312.7297
  69. Spahn F, Schmidt J, Albers N et al (2006) Cassini dust measurements at Enceladus and implications for the origin of the E ring. Science 311:1416–1418. doi:10.1126/science.1121375 ADSCrossRefGoogle Scholar
  70. Szabó GM, Szatmáry K, Divéki Z, Simon A (2006) Possibility of a photometric detection of “exomoons”. A&A 450:395–398. doi:10.1051/0004-6361:20054555, astro-ph/0601186
  71. Szabó R, Szabó GM, Dálya G et al (2013) Multiple planets or exomoons in Kepler hot Jupiter systems with transit timing variations? A&A 553:A17. doi:10.1051/0004-6361/201220132, 1207.7229
  72. Tusnski LRM, Valio A (2011) Transit model of planets with Moon and ring systems. ApJ 743:97. doi:10.1088/0004-637X/743/1/97, 1111.5599
  73. Williams DM, Knacke RF (2004) Looking for planetary Moons in the spectra of distant Jupiters. Astrobiology 4:400–403. doi:10.1089/ast.2004.4.400 ADSCrossRefGoogle Scholar
  74. Zhuang Q, Gao X, Yu Q (2012) The Rossiter-McLaughlin effect for exomoons or binary planets. ApJ 758:111. doi:10.1088/0004-637X/758/2/111, 1207.6966
  75. Zuluaga JI, Kipping DM, Sucerquia M, Alvarado JA (2015) A novel method for identifying exoplanetary rings. ApJ 803:L14. doi:10.1088/2041-8205/803/1/L14, 1502.07818

Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  1. 1.Max Planck Institute for Solar System ResearchGöttingenGermany

Personalised recommendations