TOI-733 b -- a planet in the small-planet radius valley orbiting a Sun-like star

We report the discovery of a hot ($T_{\rm eq}$ $\approx$ 1055 K) planet in the small planet radius valley transiting the Sun-like star TOI-733, as part of the KESPRINT follow-up program of TESS planets carried out with the HARPS spectrograph. TESS photometry from sectors 9 and 36 yields an orbital period of $P_{\rm orb}$ = $4.884765 _{ - 2.4e-5 } ^ { + 1.9e-5 }$ days and a radius of $R_{\mathrm{p}}$ = $1.992 _{ - 0.090 } ^ { + 0.085 }$ $R_{\oplus}$. Multi-dimensional Gaussian process modelling of the radial velocity measurements from HARPS and activity indicators, gives a semi-amplitude of $K$ = $2.23 \pm 0.26$ m s$^{-1}$, translating into a planet mass of $M_{\mathrm{p}}$ = $5.72 _{ - 0.68 } ^ { + 0.70 }$ $M_{\oplus}$. These parameters imply that the planet is of moderate density ($\rho_\mathrm{p}$ = $3.98 _{ - 0.66 } ^ { + 0.77 }$ g cm$^{-3}$) and place it in the transition region between rocky and volatile-rich planets with H/He-dominated envelopes on the mass-radius diagram. Combining these with stellar parameters and abundances, we calculate planet interior and atmosphere models, which in turn suggest that TOI-733 b has a volatile-enriched, most likely secondary outer envelope, and may represent a highly irradiated ocean world - one of only a few such planets around G-type stars that are well-characterised.Comment: Accepted for publication in A&

Reproducing the composition of Jupiter's envelope from the gas phase of the protosolar nebula

International audienceTwo decades ago, the Galileo probe performed an in situ measurement of elemental abundances in Jupiter's atmosphere, which resulted in a number of formation scenarios to explain observations [1-4]. These measurements indicated that volatile abundances of C, N, S, P, Ar, Kr and Xe were enhanced by a factor of 2 to 6 times their protosolar value, except for O that was found to be subsolar. The more recent measurements made by Juno confirmed the supersolar abundance of N, but found that a supersolar abundance of O is possible [5]. This result calls for an update of existing models and formation theories. Here, we investigate the possibility of reproducing the composition of Jupiter's envelope in the protosolar nebula (PSN).To do so, we compute the evolution of the PSN using a 1D viscous accretion disk model [6,7]. The disk is initially uniformly filled with trace species with protosolar abundances, present in the form of dust and ice grains, and their vapor. The radial transport of trace species is computed by solving an advection-diffusion equation, and phase transitions are accounted for by computing sublimation and condensation rates for each species. We then compare the composition of the PSN computed by our model with the updated measurements of elemental abundance in Jupiter.The figure below represents profiles of the H2O abundance in the disk, normalized to its initial value, at different times of the disk evolution. Solid and dashed lines are used to indicate locations where the disk is dominated by solids (solid lines) or vapor (dashed lines). The blue box corresponds to the measurement of H2O to protosolar O abundance measured in Jupiter's atmosphere by Juno [5]. Every trace species evolves in a similar fashion, but their icelines are at different heliocentric distances.We find that the composition of Jupiter's envelope can be explained only from its accretion from PSN gas or from a mixture of vapors and solids, depending on the turbulence level in the disk. Such compositions can be found at ~4 AU, namely between the icelines of H2O (3.5 AU) and CO2 (5.5 AU), and at times 100-300 kyr of the disk evolution. These results [7] are compatible with both the core accretion model and the gravitational collapse model, but give a new possible scenario of Jupiter's formation. [1] Gautier, D., Hersant, F., Mousis, O., et al. 2001, ApJL, 550, L227.[2] Mousis, O., Ronnet, T., and Lunine, J. I. 2019, ApJ, 875, 9.[3] Öberg, K. I. and Wordsworth, R. 2019, AJ, 158, 194.[4] Miguel, Y., Cridland, A., Ormel, C. W., et al. 2020, MNRAS, 491, 1998.[5] Li, C., Ingersoll, A., Bolton, S., et al. 2020, Nature Astronomy, 4, 609.[6] Aguichine, A., Mousis, O., Devouard, B., and Ronnet, T. 2020, ApJ, 901, 97.[7] Aguichine, A., Mousis, O., and Lunine, J. I. 2022, accepted in PSJ

Deciphering the composition of Jupiter's building blocks from Juno water measurements

Virtual meetingInternational audienceThe recent water and ammonia measurements (Bolton et al. 2017; Li et al. 2017, 2020) performed at 100 bars or more by the Juno microwave radiometer in the interior of Jupiter are combined with the data previously acquired by the Galileo probe (Mahaffy et al. 2000; Wong et al. 2004) and the Cassini spacecraft (Fletcher et al. 2009) to derive hints on the composition of solids vaporized in the envelope of the forming Jupiter during its growth.To do so, we computed the condensation sequence of the ices of astrophysical interest forming in the feeding zone of the growing Jupiter by using the equilibrium curves of pure condensates and various clathrates derived from compilations of laboratory data or fits from models calibrated on experiments. The employed disk model detailing the evolution of temperature and pressure at the location of Jupiter is derived from Aguichine et al. (2020). Our approach allows i) the computation of the composition of ices forming in feeding zone of Jupiter, and ii) the determination of the amount of these solids needed in the giant planet's envelope to match the measured volatiles enrichments. The Juno water measurement is used to calibrate our model.Figure 1 represents an example of volatiles enrichments in Jupiter fitted with our planetesimal composition model. In this case, we assume that the abundances of volatiles are protosolar and that only pure ices formed in the protosolar nebula. The figure shows that all species abundances, except that of argon, can be matched in Jupiter. The corresponding amount of ices vaporized in the envelope ranges between 3.9 and 20.7 Earth- masses. Other cases, with increasing water abundance in the protosolar nebula and the presence of clathrates, are currently investigated.Fig. 1.Ratio of Jovian to protosolar abundances in the case the volatiles part of the building blocks is formed from pure condensates only. Aguichine, A., Mousis, O., Devouard, B., Ronnet, T. 2020. Rocklines as Cradles for Refractory Solids in the Protosolar Nebula. The Astrophysical Journal 901. doi:10.3847/1538-4357/abaf47Bolton, S.J. and 42 colleagues 2017. Jupiter's interior and deep atmosphere: The initial pole-to-pole passes with the Juno spacecraft. Science 356, 821-825. doi:10.1126/science.aal2108Fletcher, L.N., Orton, G.S., Teanby, N.A., Irwin, P.G.J. 2009. Phosphine on Jupiter and Saturn from Cassini/CIRS. Icarus 202, 543-564. doi:10.1016/j.icarus.2009.03.023Li, C. and 22 colleagues 2020. The water abundance in Jupiter's equatorial zone. Nature Astronomy 4, 609-616. doi:10.1038/s41550-020-1009-3Li, C. and 16 colleagues 2017. The distribution of ammonia on Jupiter from a preliminary inversion of Juno microwave radiometer data. Geophysical Research Letters 44, 5317-5325. doi:10.1002/2017GL073159Mahaffy, P.R. and 7 colleagues 2000. Noble gas abundance and isotope ratios in the atmosphere of Jupiter from the Galileo Probe Mass Spectrometer. Journal of Geophysical Research 105, 15061-15072. doi:10.1029/1999JE001224Wong, M.H., Mahaffy, P.R., Atreya, S.K., Niemann, H.B., Owen, T.C. 2004. Updated Galileo probe mass spectrometer measurements of carbon, oxygen, nitrogen, and sulfur on Jupiter. Icarus 171, 153-170. doi:10.1016/j.icarus.2004.04.01

Formation of Jupiter's envelope from supersolar gas in the protoplanetary disk

International audienceThe formation mechanism of Jupiter is still uncertain, as multiple volatile accretion scenarios can reproduce its metallicity [1-4]. The Galileo mission allowed in situ measurements of the abundances of several elements (Ar, Kr, Xe, C, N, S and P), which exhibit a uniform enrichment of 2 to 5 times the protosolar abundance, and a subsolar abundance has been measured for O. Recent measurements for N and O by the Juno mission confirmed the supersolar abundance of N, but indicated that the abundance of O may also be supersolar [5]. Elemental abundances measured in the Jupiter's atmosphere are key ingredients to trace the origin of various species.Here, we investigate the possible timescale and location of Jupiter's formation using measurements of molecular and elemental abundances in its envelope. To do so, we use a 1D accretion disk model to compute the properties of the protosolar nebula (PSN) that includes radial transport of trace species, present in the form of refractory dust, a mixture of ices and their vapors, to compute the composition of the PSN [6]. We focus on the radial transport of volatile species by advection-diffusion combined with the effect of icelines, computed as sublimation/condensation rates. Initialy, the disk is uniformly filled with H2O, PH3, CO, CO2, CH4, CH3OH, NH3, N2, H2S, Ar, Kr and Xe [6,7], corresponding to the main bearers of C, N, O, P, S, Ar, Kr and Xe.As the PSN evolves, solid particles drift inward due to gas drag. Volatile species are thus efficiently transported to their respective icelines, where they sublimate. This results in supersolar abundances of volatile elements in the inner part of the PSN. We find that the composition of Jupiter's envelope can be achieved by accretion of enriched gas only, or a mixture of gas and solids, depending on the viscosity of the PSN. In both cases, the composition of the PSN matches the one measured in Jupiter's envelope in timescale that are compatible with a formation by core accretion or gravitational collapse.[1] Gautier, D., Hersant, F., Mousis, O., et al. 2001, ApJL, 550, L227.[2] Mousis, O., Ronnet, T., and Lunine, J. I. 2019, ApJ, 875, 9.[3] Öberg, K. I. and Wordsworth, R. 2019, AJ, 158, 194.[4] Miguel, Y., Cridland, A., Ormel, C. W., et al. 2020, MNRAS, 491, 1998.[5] Li, C., Ingersoll, A., Bolton, S., et al. 2020, Nature Astronomy, 4, 609.[6] Aguichine, A., Mousis, O., Devouard, B., and Ronnet, T. 2020, ApJ, 901, 97.[7] Lodders, K., Palme, H., & Gail, H.-P. 2009, Landolt Börnstein, 4B, 71

Processing of refractory species in the vicinity of rocklines

International audienceIn our solar system, meteoritical matter exhibits a variety in bulk compositions that is representative of the processing history of refractory matter in the protosolar nebula (PSN). This history is usually investigated via a thermodynamic approach, where refractory grains condense out from a hot cloud. However, in the innermost regions of the PSN the migration timescale of grains can exceed the evaporation timescale of refractory species.We investigate the role played by rocklines (condensation/sublimation lines of refractory materials) in the innermost regions of the PSN to compute the composition of drifting and evaporating grains. To do so, we compute the evolution of the PSN using a 1D viscous accretion disk model [1]. The disk is initially filled with dust that is a mixture of several refractory species of protosolar composition. This dust exists in the form of refractory grains and their vapors. The radial transport of grains is computed by solving an advection-diffusion equation, and phase transitions are accounted for by computing sublimation and condensation rates for each species. We then compare the composition of the PSN computed by our model with the composition of meteoritical bodies collected on Earth.We find that the compositional gradient in the PSN that is created by rocklines, shown in Figures 1 and 2, matches the composition of cosmic spherules, chondrules, and chondrites. Moreover, our model shows that solid matter is concentrated in the vicinity of these sublimation/condensation fronts. Although our model only focuses on the most abundant refractory species (olivine, represented in our model by its end members forsterite and fayalite; enstatite and ferrosilite pyroxenes; kamacite and taenite metal; and iron sulfide), it suggests that rocklines heavily processed refractory matter in the PSN, which has important consequences for the composition of small and large bodies in the innermost regions of the solar system. The local increase of the iron abundance close to rocklines of iron alloys could have contributed to the high Fe-content in Mercury.Figure 1. Composition profiles of the PSN in a Mg-Fe-Si ternary diagram (expressed in mass fraction) at different times, with composition of glass cosmic spherules (S-V type), barred olivine spherules (S-BO type), porphyritic spherules (S-P type) and C-chondrules. Protosolar and Earth's compositions are represented by Sun's and Earth's symbols, respectively, and Mercury's composition is represented by a red circle. Figure 2. Same as Figure 1, but here the Fe wt% is represented as a function of heliocentric distance. Color boxes correspond to typical compositions of chondrules (0%-10%), glass cosmic spherules (10%-30%), and porphyritic and barred olivine cosmic spherules (30%-60%). [1] Aguichine, A., Mousis, O., Devouard, B., and Ronnet, T. 2020, ApJ, 901, 97

The Nature and Composition of Jupiter's Building Blocks Derived from the Water Abundance Measurements by the Juno Spacecraft

The microwave radiometer on board the Juno spacecraft provided a measurement of the water abundance found to range between \raisebox-0.5ex~1 and 5.1 times the protosolar abundance of oxygen in the near-equatorial region of Jupiter. Here, we aim to combine this up-to-date oxygen determination, which is likely to be more representative of the bulk abundance than the Galileo probe subsolar value, with the other known measurements of elemental abundances in Jupiter, to derive the formation conditions and initial composition of the building blocks agglomerated by the growing planet, and that determine the heavy element composition of its envelope. We investigate several cases of formation of icy solids in the protosolar nebula (PSN), from the condensation of pure ices to the crystallization of mixtures of pure condensates and clathrates in various proportions. Each of these cases corresponds to a distinct solid composition whose amount is adjusted in the envelope of Jupiter to match the O abundance measured by Juno. The volatile enrichments can be matched by a wide range of planetesimal compositions, from solids exclusively formed from pure condensates or from nearly exclusively clathrates, the latter case providing a slightly better fit. The total mass of volatiles needed in the envelope of Jupiter to match the observed enrichments is within the \raisebox-0.5ex~4.3-39 M_\ensuremath⊕ range, depending on the crystallization scenario considered in the PSN. A wide range of masses of heavy elements derived from our fits is found to be compatible with the envelope's metallicity calculated from current interior models

A self-consistent thermodynamic approach to compute the interiors of irradiated ocean planets

International audienceA self-consistent thermodynamic approach to compute the interiors of irradiated ocean planets Planetary interior models rely on the thermodynamic properties of the used materials. Equations of states (EOSs) are key ingredients to compute internal structures, as they link the pressure and density profiles, and leave a unique solution satisfying all equations describing the interior of the planet. Often, when thermodynamic data are lacking, the formulation of EOSs allow extrapolation in both pressure and temperature. The effect of temperature on EOSs is often minor, implying that models of isothermal planets provide consistent results. This approach meets limitations in the case of fluids (liquids, gases and supercritical fluids), whose properties are very sensitive to variations in temperature. Here we propose a way to compute the relevant thermodynamic parameters in supercritical water from the most recent EOSs, in order to compute the internal structures of irradiated ocean planets, coupled with a 1D convectiveradiative atmospheric model. Our results allow a better understanding of the diversity of observed sub-Neptunes, linking their internal structure to formation conditions

The Possible Formation of Jupiter from Supersolar Gas

International audienceMore than two decades ago, the Galileo probe performed in situ measurements of the composition of Jupiter's atmosphere and found that the abundances of C, N, S, P, Ar, Kr, and Xe were all enriched by factors of 1.5-5.4 times their protosolar value. Juno's measurements recently confirmed the supersolar N abundance and also found that the O abundance was enriched by a factor 1-5 compared with its protosolar value. Here, we aim at determining the radial and temporal evolution of the composition of gases and solids in the protosolar nebula (PSN) to assess the possibility that Jupiter's current composition was acquired via the direct accretion of supersolar gases. To do so, we model the evolution of a 1D α-viscous accretion disk that includes the radial transport of dust and ice particles and their vapors, with their sublimation and condensation rates, to compute the composition of the PSN. We find that the composition of Jupiter's envelope can be explained only from its accretion from PSN gas (α ≤ 10-3), or from a mixture of vapors and solids (α > 10-3). The composition of the PSN at 4 au, namely between the locations of the H2O and CO2 icelines, reproduces the one measured in Jupiter between 100 and 300 kyr of disk evolution. Our results are found to be compatible with both the core accretion model, where Jupiter would acquire its metallicity by late accretion of volatile-rich planetesimals, and the gravitational collapse scenario, where the composition of proto-Jupiter would be similar to that of the PSN

Modeling the structure of irradiated ocean planets - implications for mass-radius relationships

International audienc

Evolution of the reservoir of volatiles in the protosolar nebula

International audienceHow volatiles were incorporated in the building blocks of planets and small bodies in the protosolar nebula (PSN) remains an outstanding question. Some scenarios consider that planetesimals formed from a mixture of refractory material and volatiles trapped in amorphous ice in the outer nebula, while others hypothesize that volatiles have been incorporated in clathrates or formed pure condensates [1,2]. Here, we study the evolution of volatiles species in the PSN (H2O, CO, CO2, CH4, H2S, N2, NH3, Ar, Kr, Xe and PH3) considering two possible volatiles reservoir in the initial state: amorphous ice (see Figure 1) or pure condensates (see Figure 2). To do so, we use a 1D disk accretion model [3] with radial transport of trace species to compute the radial distribution of volatiles in the PSN. This model includes condensation/sublimation rates of pure condensates, as well as clathration/release rates when enough crystalline water is available. Figure 1 represents the case where volatiles are initially delivered to the PSN in the form of pure condensates. Figure 2 represents the case where volatiles are delivered to the PSN by amorphous ice. Species are released when amorphous grains cross the ACTZ region. Once delivered to the disk, the phase (solid or gaseous) of each species is ruled by the positions of its corresponding condensation and clathration lines. Clathration lines of the considered volatiles are closer to the Sun than their respective condensation lines, except for CO wich have its clathration line further from the sun than its condensation line. Gaseous volatiles condense or become entrapped (depending on the availability of water ice) when diffusing outward the locations of their lines. Conversely, volatiles condensed/entrapped in grains or pebbles are released in gaseous forms when drifting inward their lines. Peaks of abundances form close to each line. Our simulations show that a significant fraction of volatiles can be trapped in clathrates, only if they have initially been delivered in pure condensate forms to the disk. We also show that several regions in the protosolar nebula share a metallicity that is consistent with those measured in the atmospheres of the ice giants [3,4]. These findings have important implications for the formation history of the outer planetsFigure 1 : Scheme showing the disk at initialization and at a given time. The volatiles are initially delivered under pure condensates and vapor. The vapor will condensate into clathrate hydrate, if there is enough crystalline water available. Grains drift inward while vapor undergo diffusion inward and outward. Leading to an accumulation of species at the place of condensation lines. Figure 2 Scheme showing the disk at initialization and at a given time. The volatiles are initially delivered trapped into amorphous ice and vapor released from amorphous ice at the Amorphous to Crystalline Transition Zone (ACTZ). The clathration line is further than the ACTZ, since there no crystalline water after the ACTZ, clathration cannot happen, or is marginal if the clathration line is close to the ACTZ.[1] : Gautier, D., Hersant, F., Mousis, O., et al. 2001, ApJL, 550, L227 [2] : Mousis, O., Ronnet, T., & Lunine, J. I. 2019, ApJ, 875, 9.[3] : Aguichine, A., Mousis, O., Devouard, B., et al. 2020, ApJ, 901, 97.[4] : Asplund, M., Grevesse, N., Sauval, A. J., et al. 2009, ARA&A, 47, 481.[5] : Irwin, P. G. J., Toledo, D., Garland, R., et al. 2018, Nature Astronomy, 2, 420