A rapid decrease in the rotation rate of comet 41P/Tuttle–Giacobini–Kresák

Published online:


Cometary outgassing can produce torques that change the spin state of the cometary nucleus, which in turn influences the evolution and lifetime of the comet1,2. If these torques increase the rate of rotation to the extent that centripetal forces exceed the material strength of the nucleus, the comet can fragment3. Torques that slow down the rotation can cause the spin state to become unstable, but if the torques persist the nucleus can eventually reorient itself and the rotation rate can increase again4. Simulations predict that most comets go through a short phase of rapid changes in spin state, after which changes occur gradually over longer times5. Here we report observations of comet 41P/Tuttle–Giacobini–Kresák during its close approach to Earth (0.142 astronomical units, approximately 21 million kilometres, on 1 April 2017) that reveal a rapid decrease in rotation rate. Between March and May 2017, the apparent rotation period of the nucleus increased from 20 hours to more than 46 hours—a rate of change of more than an order of magnitude larger than has hitherto been measured. This phenomenon must have been caused by the gas emission from the comet aligning in such a way that it produced an anomalously strong torque that slowed the spin rate of the nucleus. The behaviour of comet 41P/Tuttle–Giacobini–Kresák suggests that it is in a distinct evolutionary state and that its rotation may be approaching the point of instability.

  • Subscribe to Nature for full access:



Additional access options:

Already a subscriber?  Log in  now or  Register  for online access.


  1. 1.

    Cometary rotation: an overview. Earth Moon Planets 79, 35–53 (1997)

  2. 2.

    , , & The changing rotation period of comet 67P/Churyumov–Gerasimenko controlled by its activity. Astron. Astrophys. 579, L5 (2015)

  3. 3.

    Tidal splitting and rotational breakup of solid biaxial ellipsoids. Icarus 149, 375–383 (2001)

  4. 4.

    , , & in Comets II (eds et al.) 281–299 (Univ. Arizona Press, 2004)

  5. 5.

    , , & Long-term simulations of the rotational state of small irregular cometary nuclei. Astron. Astrophys. 406, 1123–1133 (2003)

  6. 6.

    et al. The Swift Gamma-Ray Burst mission. Astrophys. J. 611, 1005–1020 (2004)

  7. 7.

    , & The HB narrowband comet filters: standard stars and calibrations. Icarus 147, 180–204 (2000)

  8. 8.

    et al. Cyanogen jets in comet Halley. Nature 324, 649–651 (1986)

  9. 9.

    & in Comets II (eds et al.) 449–469 (Univ. Arizona Press, 2004)

  10. 10.

    et al. EPOXI at comet Hartley 2. Science 332, 1396–1400 (2011)

  11. 11.

    et al. Comet 41P/Tuttle–Giacobini–Kresák. CBET 4375 (2017)

  12. 12.

    , , & Comet 41P/Tuttle–Giacobini–Kresák. CBET 4377 (2017)

  13. 13.

    , , & in Comets II (eds et al.) 223–264 (Univ. Arizona Press, 2004)

  14. 14.

    et al. Thermal properties, sizes, and size distribution of Jupiter-family cometary nuclei. Icarus 226, 1138–1170 (2013)

  15. 15.

    SOHO SWAN derived cometary water production rates collection, urn:nasa:pds:soho:swan_derived:1.0 (ed. ) NASA Planetary Data System (2017)

  16. 16.

    , , , & The ensemble properties of comets: Results from narrowband photometry of 85 comets, 1976–1992. Icarus 118, 223–270 (1995)

  17. 17.

    & CN morphology studies of comet 103P/Hartley 2. Astron. J. 141, 183 (2011)

  18. 18.

    & Relating changes in cometary rotation to activity: current status and applications to comet C/2012 S1 (ISON). Astrophys. J. 775, L10 (2013)

  19. 19.

    Cometary evolution and cryovolcanism. Can. J. Phys. 90, 807–815 (2012)

  20. 20.

    & Further investigation of changes in cometary rotation. In Asteroids, Comets, Meteors 2017 meeting, abstr. 1.e.32, (2017)

  21. 21.

    et al. The rotation state of 67P/Churyumov–Gerasimenko from approach observations with the OSIRIS cameras on Rosetta. Astron. Astrophys. 569, L2 (2014)

  22. 22.

    41P/Tuttle–Giacobini–Kresak. Gary W. Kronk’s Cometography (2017)

  23. 23.

    , , , & Rotationally induced surface slope-Instabilities and the activation of CO2 activity on comet 103P/Hartley 2. Icarus 272, 60–69 (2016)

  24. 24.

    et al. The evolving activity of the dynamically young comet C/2009 P1 (Garradd). Astrophys. J. 786, 48 (2014)

  25. 25.

    Composite dust phase function for comets. Lowell Observatory (2010)

  26. 26.

    41P/Tuttle–Giacobini–Kresák. Seiichi Yoshida’s Home Page (2017)

  27. 27.

    & The fluorescence of cometary OH. Astrophys. J. 331, 1058–1077 (1988)

  28. 28.

    The density distribution of neutral compounds in cometary atmospheres. I. Models and equations. Astron. Astrophys. 95, 69–79 (1981)

  29. 29.

    & Vaporization of comet nuclei: light curves and life times. Moon Planets 21, 155–171 (1979)

  30. 30.

    et al. Deep Impact: excavating comet Tempel 1. Science 310, 258–264 (2005)

  31. 31.

    , , , & A quarter-century of observations of comet 10P Tempel 2 at Lowell Observatory: continued spin-down, coma morphology, production rates, and numerical modeling. Astrophys. J. 144, 153 (2012)

  32. 32.

    & Change in the rotational period of comet P/Tempel 2 between the 1988 and 1994 apparitions. Icarus 123, 463–477 (1996)

  33. 33.

    , , & Determination of a precise rotation period for the Deep Space 1 target, comet 19P/Borelly. Icarus 209, 745–752 (2010)

  34. 34.

    et al. On the nucleus structure and activity of comet 67P/Churyumov–Gerasimenko. Science 347, aaa1044 (2015)

  35. 35.

    Dynamics Team. Comet rotation period. European Space Agency (2017)

  36. 36.

    , & Comet Levy (1990c): ground-based photometric results. Icarus 94, 511–523 (1991)

  37. 37.

    , , , & Ultraviolet and visible variability of the coma of comet Levy (1990c). Icarus 95, 65–72 (1992)

Download references


We thank M. Siegel and the Swift team for planning the observations of 41P. This research was supported by Swift Guest Investigator Program grant 1316125. We thank A. Thirouin, C. Trujillo and N. Moskovitz for observing and/or donating telescope time to acquire images used to determine rotation periods from morphology. We thank N. Eisner and D. Schleicher for sharing their preliminary results with us. We thank N. Samarasinha for calculating the ζ parameter for 41P and 67P. This work made use of the Discovery Channel Telescope at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy and operates the DCT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University and Yale University. The Large Monolithic Imager was built by Lowell Observatory using funds provided by the National Science Foundation (AST-1005313). This work also made use of NASA’s Astrophysics Data System and of the JPL/Horizons ephemerides service, maintained by the JPL Solar System Dynamics group.

Author information


  1. Department of Astronomy, University of Maryland, College Park, Maryland 20742, USA

    • Dennis Bodewits
    • , Tony L. Farnham
    • , Michael S. P. Kelley
    •  & Matthew M. Knight


  1. Search for Dennis Bodewits in:

  2. Search for Tony L. Farnham in:

  3. Search for Michael S. P. Kelley in:

  4. Search for Matthew M. Knight in:


D.B. and T.L.F. designed and analysed the Swift observations. D.B., T.L.F. and M.S.P.K. planned and acquired the DCT observations. T.L.F. processed and analysed the DCT data. M.S.P.K. and D.B. modelled the change in period. All authors wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Dennis Bodewits.

Reviewer Information Nature thanks B. E. A. Mueller 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.

Extended data


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.