ON THE VOLATILE ENRICHMENTS AND HEAVY ELEMENT CONTENT IN HD189733b

Journal Article · Tue Feb 01 04:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/727/2/77· OSTI ID:21567567

Mousis, O; Petit, J -M; Picaud, S ^[1]; Lunine, J I ^[2]; Zahnle, K; Marley, M S ^[3]; Biennier, L; Mitchell, J B. A.; Cordier, D; Georges, R ^[4]; Johnson, T V ^[5]; Boudon, V ^[6]; Devel, M ^[7]; Griffith, C ^[8]; Iro, N ^[9]; Marboeuf, U ^[10]

---

1. Institut UTINAM, CNRS-UMR 6213, Observatoire de Besancon, Universite de Franche-Comte, BP 1615, 25010 Besancon Cedex (France)
2. Dipartimento di Fisica, Universita degli Studi di Roma 'Tor Vergata', Roma (Italy)
3. NASA Ames Research Center, Moffett Field, CA 94035 (United States)
4. Universite europeenne de Bretagne, Rennes (France)
5. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
6. Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS-Universite de Bourgogne, 9 Avenue Alain Savary, BP 47870, F-21078 Dijon Cedex France (France)
7. FEMTO-ST, CNRS, UFC, UTBM, ENSMM, Besancon (France)
8. Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ (United States)
9. NASA/Goddard Space Flight Center, Greenbelt, MD (United States)
10. Laboratoire de Planetologie de Grenoble, Universite Joseph Fourier, CNRS INSU (France)

Favored theories of giant planet formation center around two main paradigms, namely the core accretion model and the gravitational instability model. These two formation scenarios support the hypothesis that the giant planet metallicities should be higher or equal to that of the parent star. Meanwhile, spectra of the transiting hot Jupiter HD189733b suggest that carbon and oxygen abundances range from depleted to enriched with respect to the star. Here, using a model describing the formation sequence and composition of planetesimals in the protoplanetary disk, we determine the range of volatile abundances in the envelope of HD189733b that is consistent with the 20-80 M{sub +} of heavy elements estimated to be present in the planet's envelope. We then compare the inferred carbon and oxygen abundances to those retrieved from spectroscopy, and we find a range of supersolar values that directly fit both spectra and internal structure models. In some cases, we find that the apparent contradiction between the subsolar elemental abundances and the mass of heavy elements predicted in HD189733b by internal structure models can be explained by the presence of large amounts of carbon molecules in the form of polycyclic aromatic hydrocarbons and soots in the upper layers of the envelope, as suggested by recent photochemical models. A diagnostic test that would confirm the presence of these compounds in the envelope is the detection of acetylene. Several alternative hypotheses that could also explain the subsolar metallicity of HD189733b are formulated: the possibility of differential settling in its envelope, the presence of a larger core that did not erode with time, a mass of heavy elements lower than the one predicted by interior models, a heavy element budget resulting from the accretion of volatile-poor planetesimals in specific circumstances, or the combination of all these mechanisms.

• OSTI ID: 21567567
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 727; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
ACETYLENE
ALKYNES
AROMATICS
CARBON
ELEMENT ABUNDANCE
ELEMENTS
ENRICHMENT
HYDROCARBONS
NONMETALS
ORGANIC COMPOUNDS
OXYGEN
PLANETS
POLYCYCLIC AROMATIC HYDROCARBONS
STARS
VOLATILITY