"TNOs are cool'': A survey of the trans-Neptunian region. II. The thermal lightcurve of (136108) Haumea

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

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41 Citations (Scopus)

Abstract

Thermal emission from Kuiper belt object (136108) Haumea was measured with Herschel-PACS at 100 μm and 160 μm for almost a full rotation period. Observations clearly indicate a 100 μm thermal lightcurve with an amplitude of a factor of ~2, which is positively correlated with the optical lightcurve. This confirms that both are primarily due to shape effects. A 160 μm lightcurve is marginally detected. Radiometric fits of the mean Herschel- and Spitzer- fluxes indicate an equivalent diameter D ~ 1300 km and a geometric albedo pv ~0.70-0.75. These values agree with inferences from the optical lightcurve, supporting the hydrostatic equilibrium hypothesis. The large amplitude of the 100 μm lightcurve suggests that the object has a high projected a/b axis ratio (~1.3) and a low thermal inertia as wellas possible variable infrared beaming. This may point to fine regolith on the surface, with a lunar-type photometric behavior. The quality of the thermal data is not sufficient to clearly detect the effects of a surface dark spot. 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
Volume518
DOIs
Publication statusPublished - 01 Jul 2010

Keywords

  • Kuiper belt objects: individual: (136108) Haumea
  • techniques: photometric

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