Planet formation process as a phase transition

Local layer structures and their formation process in a half-V-shaped switching ferroelectric liquid crystal (HV-FLC) were investigated by means of synchrotron X-ray microdiffraction. The HV-FLC is a FLC that has a cholesteric–chiral smectic C (Ch–SmC*) phase transition sequences. X-ray microdiffraction measurements revealed that the SmC* phase in the HV-FLC was composed of asymmetric chevron and inclined-bookshelf structures. In addition, temperature-controlled X-ray diffraction measurements showed that the transient layer structures appeared during the Ch to SmC* phase transition.

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The origin of the obliquity in planetary systems studied with infrared interferometry

10.5194/epsc2020-61 ◽

2020 ◽

Author(s):

Stefan Kraus

Keyword(s):

Formation Process ◽

Planet Formation ◽

Rotation Axis ◽

Scattered Light ◽

Dynamical Evolution ◽

Asymmetric Structure ◽

Stellar Rotation ◽

3 Dimensional ◽

Beam Combination ◽

Infrared Interferometry

Observations of the Rossiter-McLaughlin effect have revealed that the orbits of many exoplanets are misaligned with respect to the stellar rotation axis. Various scenarios have been proposed that associate the orbit obliquity either with multi-body interactions or dynamical processes in the disc during the planet formation process. In this talk, I will present how infrared interferometry allows us to study the origin of the planet obliquity: In the first part of the talk I will present observations that reveal the recently-posted disc tearing effect, where the gravitational torque of companions on misaligned orbits can tear the disc apart into distinct rings that precess independently around the central objects. We imaged the triple system GW Orionis using VLTI, CHARA, ALMA, SPHERE, and GPI and discover three rings in thermal light and an asymmetric structure with radial shadows in scattered light. The inner-most ring is eccentric (e=0.3; 43 au radius) and strongly misaligned both with respect to the orbital planes and with respect to the outer disc. Modelling the scattered light signatures and the shape of the shadows cast by the misaligned ring allows us derive the shape and 3-dimensional orientation of the disc surface, revealing that the disc is strongly warped and breaks at a radius of about 50 au. Based on the measured triple star orbits and disc properties, we conducted smoothed particle hydrodynamic simulations which show that the system is susceptible to the disc tearing effect. The ring offers suitable conditions for planet formation, providing a mechanism for forming wide-separation planets on highly oblique orbits. Our results imply that there may exist a significant, yet undiscovered population of long-period planets on highly oblique orbits that has formed around misaligned multiple systems. In the second part I will show how infrared interferometry can be used to search for this predicted population of wide-separation planets on oblique orbits, probing a highly complementary regime to the parameter space accessible with the Rossiter-McLaughlin effect. I will present the first study where the spin-orbit alignment has been measured for a directly-imaged exoplanet, namely on Beta Pictoris b. We used VLTI/GRAVITY spectro-interferometry with an astrometric accuracy of 1 microarcsecond to measure the photocenter displacement associated with the stellar rotation. Taking inclination constraints from astroseismology into account, we constrain the 3-dimensional orientation of the stellar spin axis and find that Beta Pic b orbits its host star on a prograde orbit with a small obliquity angle.&#160; I will conclude by offering a near-term perspective on how infrared interferometry with the proposed BIFROST beam-combination instrument could advance our understanding of the planet formation process and of the early dynamical evolution of exoplanetary systems.

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Carbon-grain sublimation: a new top-down component to protostellar chemistry

10.5194/epsc2020-960 ◽

2020 ◽

Author(s):

Merel van 't Hoff ◽

Edwin Bergin ◽

Jes Jorgensen ◽

Geoffrey Blake

Keyword(s):

Gas Phase ◽

Formation Process ◽

Organic Molecules ◽

Planet Formation ◽

Protoplanetary Disks ◽

Excitation Temperature ◽

Top Down ◽

Carbon Chemistry ◽

Episodic Nature ◽

Protosolar Nebula

One of the main goals in the fields of exoplanets and planet formation is to determine the composition of terrestrial, potentially habitable, planets and to link this to the composition of protoplanetary disks. A longstanding puzzle in this regard is the Earth's severe carbon deficit; Earth is 2-4 orders of magnitude depleted in carbon compared to interstellar grains and comets. The solution to this conundrum is that carbon must have been returned to the gas phase in the inner protosolar nebula, such that it could not get accreted onto the forming bodies. A process that could be responsible is the sublimation of carbon grains at the so-called soot line (~300 K) early in the planet-formation process. I will argue that the most likely signatures of this process are an excess of hydrocarbons and nitriles inside the soot line around protostars, and a higher excitation temperature for these molecules compared to oxygen-bearing complex organics that desorb around the water snowline (~100 K). Moreover, I will show that such characteristics have indeed been reported in the literature, for example, in Orion KL, although not uniformly, potentially due to differences in observational settings or related to the episodic nature of protostellar accretion. If this process is active, this would mean that there is an heretofore unrecognized component to the carbon chemistry during the protostellar phase that is acting from the top down - starting from the destruction of larger species - instead of from the bottom up from atoms. In the presence of such a top-down component, the origin of organic molecules needs to be re-explored.&#160;

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Color Dependence of Planetary Transit Depths due to Large Starspots and Dust Clouds: Application to PTFO 8-8695

Research Notes of the AAS ◽

10.3847/2515-5172/ac391d ◽

2021 ◽

Vol 5 (11) ◽

pp. 264

Author(s):

Theodore A. Grosson ◽

Christopher M. Johns-Krull

Keyword(s):

Formation Process ◽

Direct Evidence ◽

Planet Formation ◽

Dust Clouds ◽

Multiple Wavelengths ◽

Infrared Wavelengths ◽

Planetary Transits

Abstract Although thousands of exoplanets have now been discovered, there is still a significant lack of observations of young planets only a few Myr old. Thus there is little direct evidence available to differentiate between various models of planet formation. The detection of planets of this age would provide much-needed data that could help constrain the planet formation process. To explore what transit observations of such planets may look like, we model the effects of large starspots and dust clouds on the depths of exoplanet transits across multiple wavelengths. We apply this model to the candidate planet PTFO 8-8695b, whose depths vary significantly across optical and infrared wavelengths. Our model shows that, while large starspots can significantly increase the color dependence of planetary transits, a combination of starspots and a large cloud surrounding the planet is required to reproduce the observed transit depths across four wavelengths.

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FLUCTUATIONS IN A PRIMORDIAL ANISOTROPIC ERA

International Journal of Modern Physics A ◽

10.1142/s0217751x98000159 ◽

1998 ◽

Vol 13 (03) ◽

pp. 363-379 ◽

Cited By ~ 3

Author(s):

MÁRIO NOVELLO ◽

LUCIANE R. DE FREITAS

Keyword(s):

Phase Transition ◽

Power Spectrum ◽

Galaxy Formation ◽

Formation Process ◽

Current Knowledge ◽

Efficient Process ◽

Anisotropic Expansion ◽

The Galaxy ◽

The Universe ◽

Fluid Configuration

The primordial Universe is treated in terms of a nonperfect fluid configuration endowed with an anisotropic expansion. The deGennes–Landau mechanism of phase transition acts as a very efficient process to provide the elimination of the previous anisotropy and to set the universe in the current isotropic FRW stage. The entropy produced, as a consequence of the phase transition, depends on the strength of the previous shear. We suggest the hypothesis that the germinal perturbations that will grow into the observed system of galaxies occurring in the anisotropic era. We present a model to deal with this idea that provides a power spectrum of fluctuations of the form [Formula: see text]. We compare this prediction of our model to the current knowledge on the galaxy formation process.

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On the origin of giant planets and their hosts

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310001195 ◽

2009 ◽

Vol 5 (S265) ◽

pp. 434-435

Author(s):

Misha Haywood

Keyword(s):

Formation Process ◽

Planet Formation ◽

Galactic Disk ◽

Giant Planet ◽

Solar Radius ◽

Thick Disk ◽

Giant Planets ◽

Dynamical Effect ◽

Giant Stars ◽

Metallicity Distribution

AbstractThe correlation between stellar metallicity and giant planets has been tentatively explained by the possible increase of planet formation probability in stellar disks with enhanced amount of metals. There are two caveats to this explanation. First, giant stars with planets do not show a metallicity distribution skewed towards metal-rich objects, as found for dwarfs. Second, the correlation with metallicity is not valid at intermediate metallicities, for which it can be shown that giant planets are preferentially found orbiting thick disk stars.None of these two peculiarities is explained by the proposed scenarios of giant planet formation. We contend that they are galactic in nature, and probably not linked to the formation process of giant planets. It is suggested that the same dynamical effect, namely the migration of stars in the galactic disk, is at the origin of both features, with the important consequence that most metal-rich stars hosting giant planets originate from the inner disk. A planet-metallicity correlation similar to the observed one is easily obtained if stars from the inner disk have a higher percentage of giant planets than stars born at the solar radius, with no specific dependence on metallicity. We propose that the density of H2 in the inner galactic disk (the molecular ring) could play a role in setting the high percentage of giant planets that originate from this region.

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Giant planet formation — a theoretical timeline

Symposium - International Astronomical Union ◽

10.1017/s0074180900217750 ◽

2004 ◽

Vol 202 ◽

pp. 167-174 ◽

Cited By ~ 1

Author(s):

Günther Wuchterl

Keyword(s):

Star Formation ◽

Solar System ◽

Formation Process ◽

Planet Formation ◽

Giant Planet ◽

Circumstellar Disks ◽

Giant Planets ◽

Low Mass ◽

Star Formation Regions ◽

Observational Techniques

Low mass circumstellar disks are a result of the star formation process. The growth of dust and solid planets in such pre-planetary disks determines many properties of our solar system. Models of the Solar System giant planets indicate an enrichment of heavy elements and imply heavy element cores. Detailed models therefore describe giant planet formation as a consequence of the formation of solid planets that have grown sufficiently large to permanently bind gas from the protoplanetary nebula. The diversity of Solar System and extrasolar giant planets is explained by variations in the core growth rates caused by a coupling of the dynamics of planetesimals and the contraction of the massive envelopes they dive into, as well as by changes in the hydrodynamical accretion behavior of the envelopes resulting from differences in nebula density, temperature and orbital distance. Detailed formation models are able to determine observables as luminosities, radii and effective temperatures of young giant planets. Present observational techniques do now allow to probe star formation regions at ages covering all evolutionary stages of the giant planet formation process.

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Planet formation in binary stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308016657 ◽

2007 ◽

Vol 3 (S249) ◽

pp. 251-260

Author(s):

Wilhelm Kley

Keyword(s):

Binary Stars ◽

Formation Process ◽

Planet Formation ◽

Binary Star ◽

Planetary Systems ◽

Circumstellar Disk ◽

Gravitational Action ◽

Challenging Environment ◽

Hydrodynamical Simulations

AbstractAs of today more than 30 planetary systems have been discovered in binary stars. In all cases the configuration is circumstellar, where the planets orbit around one of the stars. The formation process of planets in binary stars is more difficult than around single stars due to the gravitational action of the companion. An overview of the research done in this field will be given. The dynamical influence that a secondary companion has on a circumstellar disk, and how this affects the planet formation process in this challenging environment will be summarized. Finally, new fully hydrodynamical simulations of protoplanets embedded in disks residing in a binary star will be presented. Applications with respect to the planet orbiting the primary in the system γ Cephei will be presented.

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