On the Small Contribution of Supermicron Dust Particles to Light Scattering by Comets

Zubko, Evgenij; Videen, Gorden; Arnold, Jessica A.; MacCall, Benjamin; Weinberger, Alycia J.; Kim, Sungsoo S.

doi:10.3847/1538-4357/ab8ae4

Cited by 23 publications

(9 citation statements)

References 56 publications

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“…Due to computational limitations, the maximum grain size is not a free parameter and is set to a radius of 100 μm. This is smaller than the maximum size determined from the millimeter-wave emission model, but it is not necessary to incorporate such large sizes in the scattering model as these large grains are responsible for a negligible fraction of the scattered light (Zubko et al 2020). We use a uniform prior for each parameter.…”

Section: Markov Chain Monte Carlo Modelmentioning

confidence: 92%

Stumbling over Planetary Building Blocks: AU Microscopii as an Example of the Challenge of Retrieving Debris-disk Dust Properties

Arnold

Weinberger

Videen

et al. 2022

ApJ

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We explore whether assumptions about dust grain shape affect the resulting estimates of the composition and grain size distribution of the AU Microscopii (AU Mic) debris disk from scattered-light data collected by Lomax et al. The near edge-on orientation of the AU Mic debris disk makes it ideal for studying the effect of the scattering phase function on the measured flux ratios as a function of wavelength and projected distance. Previous efforts to model the AU Mic debris disk have invoked a variety of dust grain compositions and explored the effect of porosity, but did not undertake a systematic effort to explore a full range of size distributions and compositions to understand possible degeneracies in fitting the data. The degree to which modeling dust grains with more realistic shapes compounds these degeneracies has also not previously been explored. We find differences in the grain properties retrieved depending on the grain shape model used. We also present here our calculations of porous grains of size parameters x = 0.1 to 48 and complex refractive indices (m = n + iκ) ranging from n = 1.1 to 2.43 and k = 0 to 1.0, covering multiple compositions at visible and near-infrared wavelengths such as ice, silicates, amorphous carbon, and tholins.

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Section: Markov Chain Monte Carlo Modelmentioning

confidence: 92%

Stumbling over Planetary Building Blocks: AU Microscopii as an Example of the Challenge of Retrieving Debris-disk Dust Properties

Arnold

Weinberger

Videen

et al. 2022

ApJ

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“…There are indications that the negative polarization arises from the coherent backscattering effect of the particles (Zubko et al 2008). The single-scattering negative polarization of dust grains is stronger for small particles (below 3 µm), and it also depends on their absorption properties (Zubko 2013;Zubko et al 2020). Interestingly, the negative polarization tends to disappear when the submicrometer particles are removed from dust simulant samples (Escobar-Cerezo et al 2018) and from clouds of silicates (Muñoz et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Negative polarization properties of regolith simulants

Spadaccia

Patty

Capelo

et al. 2022

A&A

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Context. Polarization phase curves of asteroids and other small airless bodies are influenced by the compositional and physical properties of their regolith. The mixing of minerals composing the regolith influences the negative polarization at small phase angles because it changes the multiple scattering properties of the medium. Aims. This work aims to demonstrate experimentally how the mixing effect influences the polarization phase curve at small phase angles for different mineralogies relevant for asteroids, and to determine how different aggregate sizes affect the negative polarization. Methods. We prepared a set of binary and ternary mixtures with different common minerals on asteroids and one set of the same mixture with different aggregate sizes. We measured their reflected light at 530 nm with full Stokes polarimetry at phase angles ranging from 0.8°to 30°.Results. The mixing effect of the mixtures with both bright and dark minerals significantly changes the behavior of the phase curves in terms of minimum polarization, phase angle of the minimum, and inversion angle with respect to the mineral components that are mixed together. The changes in phase curve could explain the polarization observation of particular classes of asteroids (F and L class) and other asteroids with peculiar polarization curves or photometric properties. Furthermore, we demonstrate that the negative polarization is invariant to the presence of dust aggregates up to centimeter sizes.

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“…While the inversion angle is expected at 22 • and is instead seen at 32 • , a small variation in the structure and composition of the particles can extend the theoretical models of the ne gativ e branch ev en to near 40 • (e.g. Petrova, Jockers & Kiselev 2001 ;Frattin et al 2019 ;Zubko et al 2020 ;Halder & Ganesh 2021 ). Some of the aforementioned theoretical models reproduce the results more readily with compact particles rather than fluffy aggregates, although Zubko, Shkuratov & Videen ( 2015b ) argues that packing density does not have a significant effect on the polarimetric response when the particle morphology attains a significant level of disorder, when compared to the effects of refractive index.…”

Section: Effects Of the Near-sun Environmentmentioning

confidence: 79%

“…Theoretical modelling of cometary dust has been able to successfully model the observed cometary behaviour so far, with a mix of silicates and refractory organics (e.g. Kolokolova & Jockers 1997 ;Kimura, Kolokolova & Mann 2006 ;Kolokolova 2016 ;Kolokolo va, Nagdimuno v & Mackowski 2018 ;Frattin et al 2019 ;Zubko et al 2020 ). The effects of the near-Sun environment on the polarimetric properties of cometary dust, ho we v er, hav e rarely been explored before, although more general treatments of expected or observed physical and photometric beha viour ha ve been made (e.g.…”

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confidence: 99%

Polarimetric analysis of STEREO observations of sungrazing Kreutz comet C/2010 E6 (STEREO)

Nežič

Bagnulo

Jones

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Twin STEREO spacecraft pre-perihelion photometric and polarimetric observations of the sungrazing Kreutz comet C/2010 E6 (STEREO) in March 2010 at heliocentric distances 3 − 28 R⊙ were investigated using a newly-created set of analysis routines. The comet fully disintegrated during its perihelion passage. Prior to that, a broadening and an increase of the intensity peak with decreasing heliocentric distance was accompanied by a drop to zero polarisation at high phase angles (∼105–135○, STEREO-B) and the emergence of negative polarisation at low phase angles (∼25–35○, STEREO-A). Outside the near-comet region, the tail exhibited a steep slope of increasing polarisation with increasing cometocentric distance, with the slope becoming less prominent as the comet approached the Sun. The steep slope may be attributed to sublimation of refractory organic matrix and the processing of dust grains, or to presence of amorphous carbon. The change in slope with proximity to the Sun is likely caused by the gradual sublimation of all refractory material. The polarisation signatures observed at both sets of phase angles closer to the comet photocentre as the comet approached the Sun are best explained by fragmentation of the nucleus, exposing fresh Mg-rich silicate particles, followed by their gradual sublimation. The need for further studies of such comets, both observational and theoretical, is highlighted, as well as the benefit of the analysis routines created for this work.

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On the Small Contribution of Supermicron Dust Particles to Light Scattering by Comets

Cited by 23 publications

References 56 publications

Stumbling over Planetary Building Blocks: AU Microscopii as an Example of the Challenge of Retrieving Debris-disk Dust Properties

Stumbling over Planetary Building Blocks: AU Microscopii as an Example of the Challenge of Retrieving Debris-disk Dust Properties

Negative polarization properties of regolith simulants

Polarimetric analysis of STEREO observations of sungrazing Kreutz comet C/2010 E6 (STEREO)

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