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  Haumea’s thermal emission revisited in the light of the occultation results

Müller, T., Kiss, C., Alí-Lagoa, V., Ortiz, J., Lellouch, E., Santos-Sanz, P., et al. (2019). Haumea’s thermal emission revisited in the light of the occultation results. Icarus, 334, 39-51. doi:10.1016/j.icarus.2018.11.011.

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Genre: Journal Article
Other : Haumeas thermal emission revisited in the light of the occultation results

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 Creators:
Müller, T., Author
Kiss, Cs., Author
Alí-Lagoa, V., Author
Ortiz, J.L., Author
Lellouch, E., Author
Santos-Sanz, P., Author
Fornasier, S., Author
Marton, G., Author
Mommert, M., Author
Farkas-Takács, A., Author
Thirouin, A., Author
Vilenius, Esa1, Author              
Affiliations:
1Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832288              

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 Abstract: 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 We present unpublished and also reprocessed Herschel and Spitzer mid- and far-infrared measurements.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 ms (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 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.

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Language(s): eng - English
 Dates: 2019
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1016/j.icarus.2018.11.011
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Title: Icarus
Source Genre: Journal
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Publ. Info: Amsterdam : Elsevier B.V.
Pages: - Volume / Issue: 334 Sequence Number: - Start / End Page: 39 - 51 Identifier: ISSN: 0019-1035
CoNE: https://pure.mpg.de/cone/journals/resource/954922645023