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.

  • Perspective
  • Published:

The natural history of ‘Oumuamua

Abstract

The discovery of the first interstellar object passing through the Solar System, 1I/2017 U1 (‘Oumuamua), provoked intense and continuing interest from the scientific community and the general public. The faintness of ‘Oumuamua, together with the limited time window within which observations were possible, constrained the information available on its dynamics and physical state. Here we review our knowledge and find that in all cases, the observations are consistent with a purely natural origin for ‘Oumuamua. We discuss how the observed characteristics of ‘Oumuamua are explained by our extensive knowledge of natural minor bodies in our Solar System and our current knowledge of the evolution of planetary systems. We highlight several areas requiring further investigation.

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

Access options

Buy this article

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

Fig. 1: Montage of images of ‘Oumuamua showing its point-like unresolved appearance with no hint of detectable activity.
Fig. 2: Montage of potential formation scenarios of ‘Oumuamua as a natural planetesimal.
Fig. 3: Inferred interstellar object number density — for a fixed estimate of the mass density of 0.004–3 Earth masses per cubic parsec — assuming different underlying SFDs.
Fig. 4: Predicted distribution of orbital elements of natural interstellar objects detected by the primary contemporary asteroid surveys.

Similar content being viewed by others

Data availability

The authors declare that the main data supporting the findings of this study are available within the article. Extra data are available from the corresponding author upon request.

References

  1. Meech, K. J. et al. A brief visit from a red and extremely elongated interstellar asteroid. Nature 552, 378–381 (2017).

    ADS  Google Scholar 

  2. Jewitt, D. et al. Interstellar interloper 1I/2017 U1: observations from the NOT and WIYN telescopes. Astrophys. J. 850, L36 (2017).

    ADS  Google Scholar 

  3. Trilling, D. E. et al. Spitzer observations of interstellar object 1I/‘Oumuamua. Astron. J. 156, 261 (2018).

    ADS  Google Scholar 

  4. Ye, Q.-Z., Zhang, Q., Kelley, M. S. P. & Brown, P. G. 1I/2017 U1 (‘Oumuamua) is hot: imaging, spectroscopy, and search of meteor activity. Astrophys. J. Lett. 851, L5 (2017).

    ADS  Google Scholar 

  5. Bannister, M. T. et al. Col-OSSOS: colors of the interstellar planetesimal 1I/‘Oumuamua. Astrophys. J. 851, L38 (2017).

    ADS  Google Scholar 

  6. Fitzsimmons, A. et al. Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 ‘Oumuamua. Nat. Astron. 2, 133–137 (2018).

    ADS  Google Scholar 

  7. Bolin, B. T. et al. APO time-resolved color photometry of highly elongated interstellar object 1I/‘Oumuamua. Astrophys. J. Lett. 852, L2 (2018).

    ADS  Google Scholar 

  8. Moretti, P. F., Maras, A. & Folco, L. Space weathering, reddening and gardening of asteroids: a complex problem. Adv. Space Res. 40, 258–261 (2007).

    ADS  Google Scholar 

  9. Fraser, W. C. et al. The tumbling rotational state of 1I/‘Oumuamua. Nat. Astron. 2, 383–386 (2018).

    ADS  Google Scholar 

  10. Knight, M. M. et al. On the rotation period and shape of the hyperbolic asteroid 1I/‘Oumuamua (2017 U1) from its lightcurve. Astrophys. J. Lett. 851, L31 (2017).

    ADS  Google Scholar 

  11. Warner, B. D., Harris, A. W. & Pravec, P. The asteroid lightcurve database. Icarus 202, 134–146 (2009).

    ADS  Google Scholar 

  12. Fujiwara, A. et al. The rubble-pile asteroid Itokawa as observed by Hayabusa. Science 312, 1330–1334 (2006).

    ADS  Google Scholar 

  13. Lacerda, P. & Jewitt, D. C. Densities of Solar System objects from their rotational light curves. Astron. J. 133, 1393 (2007).

    ADS  Google Scholar 

  14. Zappala, V., Cellino, A., Barucci, A. M., Fulchignoni, M. & Lupishko, D. F. An analysis of the amplitude–phase relationship among asteroids. Astron. Astrophys. 231, 548–560 (1990).

    ADS  Google Scholar 

  15. McNeill, A., Trilling, D. E. & Mommert, M. Constraints on the density and internal strength of 1I/‘Oumuamua. Astrophys. J. Lett. 857, L1 (2018).

    ADS  Google Scholar 

  16. Drahus, M. et al. Tumbling motion of 1I/‘Oumuamua and its implications for the body’s distant past. Nat. Astron. 2, 407–412 (2018).

    ADS  Google Scholar 

  17. Belton, M. J. S. et al. The excited spin state of 1I/2017 U1 ‘Oumuamua. Astrophys. J. Lett. 856, L21 (2018).

    ADS  Google Scholar 

  18. Micheli, M. et al. Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua). Nature 559, 223–226 (2018).

    ADS  Google Scholar 

  19. Park, R. S., Pisano, D. J., Lazio, T. J. W., Chodas, P. W. & Naidu, S. P. Search for OH 18 cm radio emission from 1I/2017 U1 with the Green Bank Telescope. Astron. J. 155, 185 (2018).

    ADS  Google Scholar 

  20. McGlynn, T. A. & Chapman, R. D. On the nondetection of extrasolar comets. Astrophys. J. Lett. 346, L105–L108 (1989).

    ADS  Google Scholar 

  21. Engelhardt, T. et al. An observational upper limit on the interstellar number density of asteroids and comets. Astron. J. 153, 133 (2017).

    ADS  Google Scholar 

  22. Meech, K. J. et al. Inner solar system material discovered in the Oort cloud. Sci. Adv. 2, e1600038 (2016).

    ADS  Google Scholar 

  23. Jewitt, D. Project Pan-STARRS and the outer Solar System. Earth Moon Planets 92, 465–476 (2003).

    ADS  Google Scholar 

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

    ADS  Google Scholar 

  25. Pfalzner, S., Steinhausen, M. & Menten, K. Short dissipation times of proto-planetary disks: an artifact of selection effects? Astrophys. J. 793, L34 (2014).

    ADS  Google Scholar 

  26. Montesinos, B. et al. Incidence of debris discs around FGK stars in the solar neighbourhood. Astron. Astrophys. 593, A51 (2016).

    Google Scholar 

  27. Wyatt, M. C. Evolution of debris disks. Annu. Rev. Astron. Astrophys. 46, 339–383 (2008).

    ADS  Google Scholar 

  28. Raymond, S. N., Armitage, P. J., Veras, D., Quintana, E. V. & Barclay, T. Implications of the interstellar object 1I/‘Oumuamua for planetary dynamics and planetesimal formation. Mon. Not. R. Astron. Soc. 476, 3031–3038 (2018).

    ADS  Google Scholar 

  29. Raymond, S. N., Armitage, P. J. & Veras, D. Interstellar object ‘Oumuamua as an extinct fragment of an ejected cometary planetesimal. Astrophys. J. Lett. 856, L7 (2018).

    ADS  Google Scholar 

  30. Charnoz, S. & Morbidelli, A. Coupling dynamical and collisional evolution of small bodies: an application to the early ejection of planetesimals from the Jupiter–Saturn region. Icarus 166, 141–156 (2003).

    ADS  Google Scholar 

  31. Tremaine, S. in Planets Around Pulsars Vol. 36 (eds Phillips, J. A. et al.) 335–344 (Astronomical Society of the Pacific, 1993).

  32. Raymond, S. N., Armitage, P. J. & Gorelick, N. Planet–planet scattering in planetesimal disks. II. Predictions for outer extrasolar planetary systems. Astrophys. J. 711, 772–795 (2010).

    ADS  Google Scholar 

  33. Holman, M. J. & Wiegert, P. A. Long-term stability of planets in binary systems. Astron. J. 117, 621–628 (1999).

    ADS  Google Scholar 

  34. Jackson, A. P., Tamayo, D., Hammond, N., Ali-Dib, M. & Rein, H. Ejection of rocky and icy material from binary star systems: implications for the origin and composition of 1I/‘Oumuamua. Mon. Not. R. Astron. Soc. 478, L49–L53 (2018).

    ADS  Google Scholar 

  35. Vincke, K. & Pfalzner, S. Cluster dynamics largely shapes protoplanetary disk sizes. Astrophys. J. 828, 48 (2016).

    ADS  Google Scholar 

  36. Hands, T. O., Dehnen, W., Gration, A., Stadel, J. & Moore, B. The fate of planetesimal discs in young open clusters: implications for 1I/‘Oumuamua, the Kuiper belt, the Oort cloud and more. Mon. Not. R. Astron. Soc. https://doi.org/10.1093/mnras/stz1069 (2019).

  37. Veras, D. Post-main-sequence planetary system evolution. R. Soc. Open Sci. 3, 150571 (2016).

    ADS  MathSciNet  Google Scholar 

  38. Trilling, D. E. et al. Implications for planetary system formation from interstellar object 1I/2017 U1 (‘Oumuamua). Astrophys. J. Lett. 850, L38 (2017).

    ADS  Google Scholar 

  39. Do, A., Tucker, M. A. & Tonry, J. Interstellar interlopers: number density and origin of ‘Oumuamua-like objects. Astrophys. J. Lett. 855, L10 (2018).

    ADS  Google Scholar 

  40. Bialy, S. & Loeb, A. Could solar radiation pressure explain ‘Oumuamua’s peculiar acceleration? Astrophys. J. 868, L1 (2018).

    ADS  Google Scholar 

  41. Moro-Martín, A., Turner, E. L. & Loeb, A. Will the Large Synoptic Survey Telescope detect extra-solar planetesimals entering the Solar System? Astrophys. J. 704, 733–742 (2009).

    ADS  Google Scholar 

  42. Kroupa, P., Tout, C. A. & Gilmore, G. The distribution of low-mass stars in the Galactic Disc. Mon. Not. R. Astron. Soc. 262, 545–587 (1993).

    ADS  Google Scholar 

  43. Cassan, A. et al. One or more bound planets per Milky Way star from microlensing observations. Nature 481, 167–169 (2012).

    ADS  Google Scholar 

  44. 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. Preprint at https://arxiv.org/abs/1109.2497 (2011).

  45. Johnson, J. A. et al. A new planet around an M Dwarf: revealing a correlation between exoplanets and stellar mass. Astrophys. J. 670, 833–840 (2007).

    ADS  Google Scholar 

  46. Winn, J. N. & Fabrycky, D. C. The occurrence and architecture of exoplanetary systems. Annu. Rev. Astron. Astrophys. 53, 409–447 (2015).

    ADS  Google Scholar 

  47. Suzuki, D. et al. The exoplanet mass-ratio function from the MOA-II survey: discovery of a break and likely peak at a Neptune mass. Astrophys. J. 833, 145 (2016).

    ADS  Google Scholar 

  48. Zhang, S. et al. The Disk Substructures at High Angular Resolution Project (DSHARP). VII. The planet–disk interactions interpretation. Astrophys. J. Lett. 869, L47 (2018).

    ADS  Google Scholar 

  49. Izidoro, A., Morbidelli, A., Raymond, S. N., Hersant, F. & Pierens, A. Accretion of Uranus and Neptune from inward-migrating planetary embryos blocked by Jupiter and Saturn. Astron. Astrophys. 582, A99 (2015).

    ADS  Google Scholar 

  50. Moro-Martín, A. Origin of 1I/‘Oumuamua. I. An ejected protoplanetary disk object? Astrophys. J. 866, 131 (2018).

    ADS  Google Scholar 

  51. Moro-Martín, A. Origin of 1I/‘Oumuamua. II. An ejected exo-oort cloud object? Astron. J. 157, 86 (2019).

    ADS  Google Scholar 

  52. Rafikov, R. R. 1I/2017 ’Oumuamua-like interstellar asteroids as possible messengers from dead stars. Astrophys. J. 861, 35 (2018).

    ADS  Google Scholar 

  53. Burgasser, A. J. et al. The Brown Dwarf Kinematics Project (BDKP). IV. Radial velocities of 85 late-M and L dwarfs with MagE. Astrophys. J. Suppl. Ser. 220, 18 (2015).

    ADS  Google Scholar 

  54. Anguiano, B., Majewski, S. R., Freeman, K. C., Mitschang, A. W. & Smith, M. C. The velocity ellipsoid in the Galactic Disc using Gaia DR1. Mon. Not. R. Astron. Soc. 474, 854–865 (2018).

    ADS  Google Scholar 

  55. Portegies Zwart, S., Torres, S., Pelupessy, I., Bédorf, J. & Cai, M. X. The origin of interstellar asteroidal objects like 1I/2017 U1 ‘Oumuamua. Mon. Not. R. Astron. Soc. 479, L17–L22 (2018).

    ADS  Google Scholar 

  56. Almeida-Fernandes, F. & Rocha-Pinto, H. J. A kinematical age for the interstellar object 1I/‘Oumuamua. Mon. Not. R. Astron. Soc. 480, 4903–4911 (2018).

    ADS  Google Scholar 

  57. Meech, K. J. & Svoren, J. in Comets II (eds Festou, M. C. et al.) 317–335 (University of Arizona Press, 2004).

  58. Pätzold, M. et al. The nucleus of comet 67P/Churyumov-Gerasimenko — Part I: The global view — nucleus mass, mass loss, porosity and implications. Mon. Not. R. Astron. Soc. 483, 2337–2346 (2019).

    ADS  Google Scholar 

  59. Seligman, D., Laughlin, G. & Batygin, K. On the anomalous acceleration of 1I/2017 U1 ‘Oumuamua. Astrophys. J. Lett. 876, L26 (2019).

    ADS  Google Scholar 

  60. Fernández, Y. R. et al. Physical properties of the nucleus of comet 2P/Encke. Icarus 147, 145–160 (2000).

    ADS  Google Scholar 

  61. Sekanina, Z. Comet Bowell (1980b) — an active-looking dormant object. Astron. J. 87, 161–169 (1982).

    ADS  Google Scholar 

  62. Fink, U. Comet Yanaka (1988r) — a new class of carbon-poor comet. Science 257, 1926–1929 (1992).

    ADS  Google Scholar 

  63. Schleicher, D. G. The extremely anomalous molecular abundances of comet 96P/Machholz 1 from narrowband photometry. Astron. J. 136, 2204–2213 (2008).

    ADS  Google Scholar 

  64. A’Hearn, M. F. et al. Cometary volatiles and the origin of comets. Astrophys. J. 758, 29 (2012).

    ADS  Google Scholar 

  65. Ootsubo, T. et al. AKARI near-infrared spectroscopic survey for CO2 in 18 comets. Astrophys. J. 752, 15 (2012).

    ADS  Google Scholar 

  66. Biver, N. et al. The extraordinary composition of the blue comet C/2016 R2 (PanSTARRS). Astron. Astrophys. 619, A127 (2018).

    Google Scholar 

  67. Seligman, D. & Laughlin, G. The feasibility and benefits of in situ exploration of ‘Oumuamua-like objects. Astron. J. 155, 217 (2018).

    ADS  Google Scholar 

  68. Rickman, H., Kamel, L., Froeschle, C. & Festou, M. C. Nongravitational effects and the aging of periodic comets. Astron. J. 102, 1446–1463 (1991).

    ADS  Google Scholar 

  69. Nesvorný, D. et al. Origin and evolution of short-period comets. Astrophys. J. 845, 27 (2017).

    ADS  Google Scholar 

  70. Micheli, M., Tholen, D. J. & Elliott, G. T. Detection of radiation pressure acting on 2009 BD. N. Astron. 17, 446–452 (2012).

    ADS  Google Scholar 

  71. Sekanina, Z. & Kracht, R. Preperihelion outbursts and disintegration of comet C/2017 S3 (Pan-STARRS). Preprint at https://arxiv.org/abs/1812.07054 (2018).

  72. Moro-Martín, A. Could 1I/‘Oumuamua be an icy fractal aggregate? Astrophys. J. Lett. 872, L32 (2019).

    ADS  Google Scholar 

  73. Loeb, A. Six strange facts about ‘Oumuamua. Preprint at https://arxiv.org/abs/1811.08832 (2018).

  74. Siraj, A. & Loeb, A. ‘Oumuamua’s geometry could be more extreme than previously inferred. Res. Notes Am. Astron. Soc. 3, 15 (2019).

    ADS  Google Scholar 

  75. Thomas, C. A. et al. ExploreNEOs. V. Average albedo by taxonomic complex in the near-Earth asteroid population. Astron. J. 142, 85 (2011).

    ADS  Google Scholar 

  76. Kokotanekova, R. et al. Rotation of cometary nuclei: new light curves and an update of the ensemble properties of Jupiter-family comets. Mon. Not. R. Astron. Soc. 471, 2974–3007 (2017).

    ADS  Google Scholar 

  77. Katz, J. I. Why is interstellar object 1I/2017 U1 (‘Oumuamua) rocky, tumbling and possibly very prolate? Mon. Not. R. Astron. Soc. 478, L95–L98 (2018).

    ADS  Google Scholar 

  78. Ćuk, M. 1I/ ‘Oumuamua as a tidal disruption fragment from a binary star system. Astrophys. J. Lett. 852, L15 (2018).

    ADS  Google Scholar 

  79. Domokos, G., Sipos, A. Á., Szabó, G. M. & Várkonyi, P. L. Formation of sharp edges and planar areas of asteroids by polyhedral abrasion. Astrophys. J. Lett. 699, L13–L16 (2009).

    ADS  Google Scholar 

  80. Vavilov, D. E. & Medvedev, Y. D. Dust bombardment can explain the extremely elongated shape of 1I/‘Oumuamua and the lack of interstellar objects. Mon. Not. R. Astron. Soc. Lett. 484, L75–L78 (2019).

    ADS  Google Scholar 

  81. Sugiura, K., Kobayashi, H. & Inutsuka, S.-i. Collisional elongation: possible origin of extremely elongated shape of 1I/’Oumuamua. Icarus 328, 14–22 (2019).

    ADS  Google Scholar 

  82. Stern, S. A. et al. Overview of initial results from the reconnaissance flyby of a Kuiper belt planetesimal: 2014 MU69. Preprint at arXiv https://arxiv.org/abs/1901.02578 (2019).

  83. Pravec, P. et al. Tumbling asteroids. Icarus 173, 108–131 (2005).

    ADS  Google Scholar 

  84. Kwiecinski, J. A., Krause, A. L. & Van Gorder, R. A. Effects of tidal torques on 1I/2017 U1 (‘Oumuamua). Icarus 311, 170–174 (2018).

    ADS  Google Scholar 

  85. Rafikov, R. R. Spin evolution and cometary interpretation of the interstellar minor object 1I/2017 ‘Oumuamua. Astrophys. J. Lett. 867, L17 (2018).

    ADS  Google Scholar 

  86. Bailer-Jones, C. A. L. et al. Plausible home stars of the interstellar object ‘Oumuamua found in Gaia DR2. Astron. J. 156, 205 (2018).

    ADS  Google Scholar 

  87. Zuluaga, J. I., Sánchez-Hernández, O., Sucerquia, M. & Ferrín, I. A general method for assessing the origin of interstellar small bodies: the case of 1I/2017 U1 (‘Oumuamua). Astron. J. 155, 236 (2018).

    ADS  Google Scholar 

  88. Dybczyński, P. A. & Królikowska, M. Investigating the dynamical history of the interstellar object ‘Oumuamua. Astron. Astrophys. 610, L11 (2018).

    ADS  Google Scholar 

  89. Zhang, Q. Prospects for backtracing 1I/‘Oumuamua and future interstellar objects. Astrophys. J. Lett. 852, L13 (2018).

    ADS  Google Scholar 

  90. Gaidos, E. What and whence 1I/‘Oumuamua: a contact binary from the debris of a young planetary system? Mon. Not. R. Astron. Soc. 477, 5692–5699 (2018).

    ADS  Google Scholar 

  91. Feng, F. & Jones, H. R. A. ‘Oumuamua as a messenger from the local association. Astrophys. J. Lett. 852, L27 (2018).

    ADS  Google Scholar 

  92. Cook, N. V., Ragozzine, D., Granvik, M. & Stephens, D. C. Realistic detectability of close interstellar comets. Astrophys. J. 825, 51 (2016).

    ADS  Google Scholar 

  93. Simon, J. B., Armitage, P. J., Youdin, A. N. & Li, R. Evidence for universality in the initial planetesimal mass function. Astrophys. J. Lett. 847, L12 (2017).

    ADS  Google Scholar 

  94. Schäfer, U., Yang, C.-C. & Johansen, A. Initial mass function of planetesimals formed by the streaming instability. Astron. Astrophys. 597, A69 (2017).

    Google Scholar 

  95. Dohnanyi, J. S. Collisional model of asteroids and their debris. J. Geophys. Res. 74, 2531–2554 (1969).

    ADS  Google Scholar 

  96. Pajola, M. et al. Size-frequency distribution of boulders ≥7 m on comet 67P/Churyumov-Gerasimenko. Astron. Astrophys. 583, A37 (2015).

    Google Scholar 

Download references

Acknowledgements

We thank the International Space Science Institute (ISSI Bern), which made this collaboration possible. A.F., M.T.B. and C.S. acknowledge support from UK Science and Technology Facilities Council grants ST/P0003094/1 and ST/L004569/1. K.J.M. acknowledges support through NSF awards AST1617015, in addition to support for HST programmes GO/DD-15405 and -15447 provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA contract NAS 5-26555. Q.Y. is supported by the GROWTH project funded by the National Science Foundation under Grant No. 1545949. This research was partially supported by the project 2015/17/B/ST9/01790 funded by the National Science Centre in Poland. M.M.K. acknowledges support from NASA Near Earth Object Observations grant no. NNX17AK15G. A.G.-L. acknowledges funding from the European Research Council under grant agreement no. 802699. A.M. and D.E.T. are supported in part by Spitzer/NASA through an award issued by JPL/Caltech. S.N.R. acknowledges helpful discussions with P. Armitage related to the interstellar object number/mass density, and the Virtual Planetary Laboratory research team, funded by the NASA Astrobiology Program under NASA Grant Number 80NSSC18K0829. This work benefited from participation in the NASA Nexus for Exoplanet Systems Science research coordination network.

Author information

Authors and Affiliations

Consortia

Contributions

M.M.K. and A.F. organized the ISSI team. K.J.M. created Figs. 1 and 2. S.N.R. conducted the modelling of inferred interstellar object number density and created Fig. 3. M.M.K., A.F. and R.J. created Fig. 4 from source data provided by T. Engelhardt. All authors discussed the topics in the paper, contributed to the writing and commented on the manuscript at all stages.

Corresponding author

Correspondence to Matthew M. Knight.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information: Nature Astronomy thanks Olivier Hainaut and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

The ‘Oumuamua ISSI Team. The natural history of ‘Oumuamua. Nat Astron 3, 594–602 (2019). https://doi.org/10.1038/s41550-019-0816-x

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41550-019-0816-x

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