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.

The trans-neptunian object UB313 is larger than Pluto

Abstract

The most distant known object in the Solar System, 2003 UB313 (97 au from the Sun), was recently discovered near its aphelion1. Its high eccentricity and inclination to the ecliptic plane, along with its perihelion near the orbit of Neptune, identify it as a member of the ‘scattered disk’. This disk of bodies probably originates in the Kuiper belt objects, which orbit near the ecliptic plane in circular orbits between 30 and 50 au, and may include Pluto as a member. The optical brightness of 2003 UB313, if adjusted to Pluto's distance, is greater than that of Pluto, which suggested that it might be larger than Pluto2. The actual size, however, could not be determined from the optical measurements because the surface reflectivity (albedo) was unknown. Here we report observations of the thermal emission of 2003 UB313 at a wavelength of 1.2 mm, which in combination with the measured optical brightness leads to a diameter of 3,000 ± 300 ± 100 km. Here the first error reflects measurement uncertainties, while the second derives from the unknown object orientation. This makes 2003 UB313 the largest known trans-neptunian object, even larger than Pluto (2,300 km)3. The albedo is 0.60 ± 0.10 ± 0.05, which is strikingly similar to that of Pluto, suggesting that the methane seen in the optical spectrum2 causes a highly reflective icy surface.

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: Time-averaged signals of the 104 bolometers as a function of time, summarizing our 1.2 mm observations.

References

  1. 1

    Brown, M. E., Trujillo, C. A. & Rabinowitz, D. IAU Circ. 8577 (2005)

  2. 2

    Brown, M. E., Trujillo, C. A. & Rabinowitz, D. L. Discovery of a planetary-sized object in the scattered Kuiper Belt. Preprint at http://arXiv.org/astro-ph/0508633 (2005)

  3. 3

    Young, E. F. & Binzel, R. Comparative mapping of Pluto's sub-Charon hemisphere — three least squares models based on mutual event lightcurves. Icarus 102, 134–149 (1994)

    ADS  Article  Google Scholar 

  4. 4

    Bowell, E., et al. in Asteroids II (eds Binzel, R., Gehrels, T. & Matthews, M.) 549–554 (Univ. Arizona Press, Tucson, 1989)

    Google Scholar 

  5. 5

    Altenhoff, W., Bertoldi, F. & Menten, K. M. Size estimates of some optically bright KBOs. Astron. Astrophys. 415, 771–775 (2004)

    ADS  Article  Google Scholar 

  6. 6

    Stansberry, J. A. et al. Albedos, diameters (and the density) of Kuiper Belt and Centaur objects. Bull. Am. Astron. Soc. 37, 737 (2005)

    ADS  Google Scholar 

  7. 7

    Tholen, D. J. & Tedesco, E. F. Pluto's lightcurve: Results from four oppositions. Icarus 108, 200–208 (1994)

    ADS  Article  Google Scholar 

  8. 8

    JPL HORIZONS on-line solar system data and ephemeris computation service. http://ssd.jpl.nasa.gov/horizons.html (accessed November 2005).

  9. 9

    Brown, M. E. et al. Satellites of the brightest Kuiper belt objects. Preprint at http://arXiv.org/astro-ph/0510029 (2005).

  10. 10

    Rabinowitz, D. L. et al. Photometric observations constraining the size, shape, and albedo of 2003 El61, a rapidly rotating, Pluto-sized object in the Kuiper Belt. Preprint at http://arXiv.org/astro-ph/0509401 (2005).

  11. 11

    Sheppard, S. S. & Jewitt, D. C. Time-resolved photometry of Kuiper Belt Objects: rotations, shapes, and phase functions. Astron. J. 124, 1757–1775 (2002)

    ADS  Article  Google Scholar 

  12. 12

    Reinsch, K., Burwitz, V. & Festou, M. C. Albedo maps of Pluto and improved physical parameters of the Pluto-Charon system. Icarus 108, 209–218 (1994)

    ADS  Article  Google Scholar 

  13. 13

    Tedesco, E. F. in Asteroids II (eds Binzel, R., Gehrels, T. & Matthews, M.) 1090–1093 (Univ. Arizona Press, Tucson, 1989)

    Google Scholar 

Download references

Acknowledgements

We are grateful to the IRAM Director for providing discretionary observing time for this project, to the bolometer technology group of E. Kreysa for providing MAMBO, and to R. Zylka for the MOPSIC data reduction package. We thank M. Brown for input and discussions.

Author information

Affiliations

Authors

Corresponding author

Correspondence to F. Bertoldi.

Ethics declarations

Competing interests

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

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Bertoldi, F., Altenhoff, W., Weiss, A. et al. The trans-neptunian object UB313 is larger than Pluto. Nature 439, 563–564 (2006). https://doi.org/10.1038/nature04494

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

Quick links