.TNOs are Cool. A survey of the trans-Neptunian region: III. Thermophysical properties of 90482 Orcus and 136472 Makemake

T. L. Lim, J. Stansberry, T. G. Müller, M. Mueller, E. Lellouch, C. Kiss, P. Santos-Sanz, E. Vilenius, S. Protopapa, R. Moreno, A. Delsanti, R. Duffard, S. Fornasier, O. Groussin, A. W. Harris, F. Henry, J. Horner, P. Lacerda, M. Mommert, J. L. OrtizM. Rengel, A. Thirouin, D. Trilling, A. Barucci, J. Crovisier, A. Doressoundiram, E. Dotto, P. J. Gutiérrez Buenestado, O. Hainaut, P. Hartogh, D. Hestroffer, M. Kidger, L. Lara, B. M. Swinyard, N. Thomas

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


Context. The goal of the Herschel open time programme "TNOs are Cool!" is to derive the physical and thermal properties for a large sample of Centaurs, and trans-Neptunian objects (TNOs), including resonant, classical, detached and scattered disk objects. Aims. Based on observations of two targets we tried (i) to optimise the SPIRE observing technique for faint (close to the background confusion noise), slowly moving targets; (ii) to test different thermal model techniques; (iii) to determine radiometric diameter and albedo values; (iv) to compare with Spitzer results whenever possible. Methods. We obtained SPIRE photometry on two targets and PACS photometry on one of the targets. Results. We present results for the two targets, (90482) Orcus and (136472) Makemake, observed with SPIRE and for one of those targets, Makemake, observed with PACS. We adopt pV = 0.27 and D = 850 km as our best estimate of the albedo and diameter of Orcus using single terrain models. With two-terrain models for Makemake, the bright terrain is fitted by, 0.78 < pV < 0.90, and the dark terrain 0.02 < pV < 0.12, giving 1360 < D < 1480 km. Conclusions. A single terrain model was derived for Orcus through the SPIRE photometry combined with MIPS data. The Makemake data from MIPS, PACS and SPIRE combined are not compatible with a single terrain model, but can be modelled with a two-terrain fit. These science demonstration observations have shown that the scanning technique, which allows us to judge the influence of background structures, has proved to be a good basis for this key programme.

Original languageEnglish (US)
Article numberL148
JournalAstronomy and Astrophysics
Issue number2
StatePublished - Jul 16 2010


  • Infrared: general
  • Kuiper belt objects: individual: 136472 Makemake
  • Kuiper belt objects: individual: 90482 Orcus
  • Submillimeter: general
  • Techniques: photometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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