``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

50 Citations (Scopus)


Context. The goal of the Herschel open time programme “TNOs areCool!” 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. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
Original languageEnglish
JournalAstronomy and Astrophysics
Publication statusPublished - 01 Jul 2010


  • techniques: photometric
  • Kuiper belt objects: individual: 90482 Orcus
  • Kuiper belt objects: individual: 136472 Makemake
  • infrared: general
  • submillimeter: general


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