Photophoresis of dust aggregates in protoplanetary disks

Borstel, Ingo von; Blum, Jürgen

doi:10.1051/0004-6361/201219622

Cited by 16 publications

(11 citation statements)

References 31 publications

(52 reference statements)

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“…Experiments in the drop tower Bremen by Wurm et al (2008) showed this clearly as 1mm size silicate particles were accelerated upon illumination while 1mm steel particles did not show a measurable motion due to photophoresis. Aggregates of particles have lower thermal conductivities by 1 to 3 orders of magnitude (Presley & Christensen 1997;Krause et al 2011;von Borstel & Blum 2012). This is valid for aggregates consisting of silicates as well as aggregates consisting of metals.…”

Section: Photophoretic Basicsmentioning

confidence: 78%

Photophoretic Separation of Metals and Silicates: The Formation of Mercury-Like Planets and Metal Depletion in Chondrites

Wurm

Trieloff

Rauer

2013

ApJ

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Mercury's high uncompressed mass density suggests that the planet is largely composed of iron, either bound within metal (mainly Fe-Ni), or iron sulfide. Recent results from the MESSENGER mission to Mercury imply a low temperature history of the planet which questions the standard formation models of impact mantle stripping or evaporation to explain the high metal content. Like Mercury, the two smallest extrasolar rocky planets with mass and size determination, CoRoT-7b and Kepler-10b, were found to be of high density.As they orbit close to their host stars this indicates that iron rich inner planets might not be a nuisance of the solar system but be part of a general scheme of planet formation. From undifferentiated chondrites it is also known that the metal to silicate ratio is highly variable which must be ascribed to pre-planetary fractionation processes. Due to this fractionation most chondritic parent bodies -most of them originated in the asteroid belt -are depleted in iron relative to average solar system abundances. The astrophysical processes leading to metal silicate fractionation in the solar nebula are essentially unknown. Here, we consider photophoretic forces. As these forces particularly act on irradiated solids, they might play a significant role for the composition of planetesimals forming at the inner edge of protoplanetary discs. Photophoresis can separate high thermal conductivity materials (iron) from lower thermal conductivity solids (silicate). We suggest that the silicates are preferentially pushed into the optical thick disk. Subsequent planetesimal formation at the edge moving outwards leads to metal rich planetesimals close to the star and metal depleted planetesimals further out in the nebula.

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Section: Photophoretic Basicsmentioning

confidence: 78%

Photophoretic Separation of Metals and Silicates: The Formation of Mercury-Like Planets and Metal Depletion in Chondrites

Wurm

Trieloff

Rauer

2013

ApJ

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“…Fig. 6a also shows a trend of small aggregates experiencing a slightly larger force than spheres of the same size, though this is less than a factor 10 as deduced by von Borstel & Blum (2012).…”

Section: C O M Pa R I S O N To E X P E R I M E N T S D I S C U S mentioning

confidence: 55%

“…The parameter β represents the ability of porous aggregates to sustain larger temperature gradients, as suggested by experimental results (von Borstel & Blum 2012). In these simulations, β = 1 − 9 log( σ ), thus β ranges from 0 for a compact aggregate ( σ = 1) to 10 for an open, fluffy aggregate ( σ = 0.1).…”

Section: Temperature Gradientmentioning

confidence: 88%

Photophoretic force on aggregate grains

Matthews

Kimery

Wurm

et al. 2015

Mon. Not. R. Astron. Soc.

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The photophoretic force may impact planetary formation by selectively moving solid particles based on their composition and structure. This generates collision velocities between grains of different sizes and sorts the dust in protoplanetary discs by composition. This numerical simulation studied the photophoretic force acting on fractal dust aggregates of µm-scale radii. Results show that aggregates tend to have greater photophoretic drift velocities than spheres of similar mass or radii, though with a greater spread in the velocity. While the drift velocities of compact aggregates continue to increase as the aggregates grow larger in size, fluffy aggregates have drift velocities which are relatively constant with size. Aggregates formed from an initially polydisperse size distribution of dust grains behave differently from aggregates formed from a monodisperse population, having smaller drift velocities with directions which deviate substantially from the direction of illumination. Results agree with microgravity experiments which show the difference of photophoretic forces with aggregation state.

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“…In this context, it is interesting to take a look at the experiments of von Borstel & Blum (2012). The authors studied the effect of photophoresis (force due to insolation heating and gas interaction) on dust aggregates of the same sizes as found in our work.…”

Section: Interpretation Of Accelerationmentioning

confidence: 77%

Characterization of dust aggregates in the vicinity of the Rosetta spacecraft

Güttler

Hasselmann

et al. 2017

Monthly Notices of the Royal Astronomical Society

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In a Rosetta/OSIRIS imaging activity in 2015 June, we have observed the dynamic motion of particles close to the spacecraft. Due to the focal setting of the OSIRIS wide angle camera, these particles were blurred, which can be used to measure their distances to the spacecraft. We detected 109 dust aggregates over a 130 min long sequence, and find that their sizes are around a millimetre and their distances cluster between 2 and 40 m from the spacecraft. Their number densities are about a factor 10 higher than expected for the overall coma and highly fluctuating. Their velocities are small compared to the spacecraft orbital motion and directed away from the spacecraft, towards the comet. From this we conclude that they have interacted with the spacecraft and assess three possible scenarios. In the likeliest of the three scenarios, centimetre-sized aggregates collide with the spacecraft and we would observe the fragments. Ablation of a dust layer on the spacecraft's z panel (remote instrument viewing direction) when rotated towards the Sun is a reasonable alternative. We could also measure an acceleration for a subset of 18 aggregates, which is directed away from the Sun and can be explain by a rocket effect, which requires a minimum ice fraction of the order of 0.1 per cent.

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Photophoresis of dust aggregates in protoplanetary disks

Cited by 16 publications

References 31 publications

Photophoretic Separation of Metals and Silicates: The Formation of Mercury-Like Planets and Metal Depletion in Chondrites

Photophoretic Separation of Metals and Silicates: The Formation of Mercury-Like Planets and Metal Depletion in Chondrites

Photophoretic force on aggregate grains

Characterization of dust aggregates in the vicinity of the Rosetta spacecraft

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