1. Haumea’s thermal emission revisited in the light of the occultation results
- Author
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Victor Ali-Lagoa, Sonia Fornasier, Pablo Santos-Sanz, Emmanuel Lellouch, Audrey Thirouin, Cs. Kiss, Gábor Marton, Michael Mommert, Esa Vilenius, J. L. Ortiz, A. Farkas-Takács, Th. Müller, European Commission, Ministerio de Ciencia e Innovación (España), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[PHYS]Physics [physics] ,Earth and Planetary Astrophysics (astro-ph.EP) ,Physics ,010504 meteorology & atmospheric sciences ,Haumea ,Dwarf planet ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Occultation ,Root mean square ,Pluto ,Amplitude ,13. Climate action ,Space and Planetary Science ,0103 physical sciences ,Thermal ,Satellite ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,010303 astronomy & astrophysics ,ComputingMilieux_MISCELLANEOUS ,Astrophysics - Earth and Planetary Astrophysics ,0105 earth and related environmental sciences - Abstract
This work is licensed under a CC-BY-NC-ND (https://creativecommons.org/licenses/by-nc-nd/4.0/), A recent multi-chord occultation measurement of the dwarf planet (136108) Haumea (Ortiz et al., 2017) revealed an elongated shape with the longest axis comparable to Pluto's mean diameter. The chords also indicate a ring around Haumea's equatorial plane, where its largest moon, Hi'iaka, is also located. The Haumea occultation size estimate (size of an equal-volume sphere1 Dequ = 1595 km) is larger than previous radiometric solutions (equivalent sizes in the range between 1150 and 1350 km), which lowers the object's density to about 1.8 g/cm3, a value closer to the densities of other large TNOs. We present unpublished and also reprocessed Herschel and Spitzer mid- and far-infrared measurements. We compare 100 and 160 µm thermal lightcurve amplitudes - originating from Haumea itself - with models of the total measured system fluxes (ring, satellite, Haumea) from 24–350 µm. The combination with results derived from the occultation measurements allows us to reinterpret the object's thermal emission. Our radiometric studies show that Haumea's crystalline water ice surface must have a thermal inertia of about 5 J K−1 m−2s−1/2 (combined with a root mean square of the surface slopes of 0.2). We also have indications that the satellites (at least Hi'iaka) must have high geometric albedos ≳ 0.5, otherwise the derived thermal amplitude would be inconsistent with the total measured system fluxes at 24, 70, 100, 160, 250, and 350 µm. The high albedos imply sizes of about 300 and 150 km for Hi'iaka and Namaka, respectively, indicating unexpectedly high densities > 1.0 g cm−3 for TNOs this small, and the assumed collisional formation from Haumea's icy crust. We also estimated the thermal emission of the ring for the time period 1980–2030, showing that the contribution during the Spitzer and Herschel epochs was small, but not negligible. Due to the progressive opening of the ring plane, the ring emission will be increasing in the next decade when JWST is operational. In the MIRI 25.5 µm band it will also be possible to obtain a very high-quality thermal lightcurve to test the derived Haumea properties. © 2018 Elsevier Inc., The research leading to these results has received funding from the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378. Funding from the Spanish grant AYA-2017-89637-R is acknowledged.
- Published
- 2019