Polarimetry of comets: A review

Dobrovolsky, O. V.; Kiselev, N. N.; Chernova, G. P.

doi:10.1007/bf00055135

Cited by 26 publications

(7 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…• The linear polarization p(θ) is a bell-shaped curve as function of scattering angle, with typical maximum value of 10 − 30% (Dobrovolsky et al 1986;Levasseur-Regourd et al 1996), although gas contamination in polarimetric measurements with wide-band filters might depolarize the observed scattered light (Kiselev et al 2004).…”

Section: Cometary Dustmentioning

confidence: 99%

Modeling Porous Dust Grains With Ballistic Aggregates. Ii. Light Scattering Properties

Shen

Draine

Johnson

2009

ApJ

View full text Add to dashboard Cite

We study the light scattering properties of random ballistic aggregates constructed in Shen et al. (Paper I).Using the discrete-dipole-approximation, we compute the scattering phase function and linear polarization for random aggregates with various sizes and porosities, and with two different compositions: 100% silicate and 50% silicate-50% graphite. We investigate the dependence of light scattering properties on wavelength, cluster size and porosity using these aggregate models. We find that while the shape of the phase function depends mainly on the size parameter of the aggregates, the linear polarization depends on both the size parameter and the porosity of the aggregates, with increasing degree of polarization as the porosity increases. Contrary to previous studies, we argue that monomer size has negligible effects on the light scattering properties of ballistic aggregates, as long as the constituent monomer is smaller than the incident wavelength up to 2πa 0 /λ ∼ 1.6 where a 0 is the monomer radius. Previous claims for such monomer size effects are in fact the combined effects of size parameter and porosity. Finally, we present aggregate models that can reproduce the phase function and polarization of scattered light from the AU Mic debris disk and from cometary dust, including the negative polarization observed for comets at scattering angles 160 • θ < 180 • . These aggregates have moderate porosities, P ≈ 0.6, and are of sub-µm-size for the debris disk case, or µm-size for the comet case.

show abstract

Section: Cometary Dustmentioning

confidence: 99%

Modeling Porous Dust Grains With Ballistic Aggregates. Ii. Light Scattering Properties

Shen

Draine

Johnson

2009

ApJ

View full text Add to dashboard Cite

show abstract

“…3. Linear polarization shows a bell-shaped curve in relation to the scattering angle with its maximum value of typically 10-30% (Dobrovolsky et al 1986;Levasseur-Regourd et al 1996). The maximum lies in a scattering angle between 80 and 90…”

Section: Introductionmentioning

confidence: 99%

Light scattering by cometary dust numerically simulated with aggregate particles consisting of identical spheres

Kimura¹,

Kolokolova²,

Mann³

2006

A&A

109

126

View full text Add to dashboard Cite

Context. Optical characterization of dust particles in cometary comae is based on a comparison between observations and simulations of solar radiation scattered by cometary dust. Aims. Our recent studies suggest that all the observed features can be reproduced by dust aggregates consisting of optically dark submicrometersize grains when the overall sizes of the aggregates are much larger than visible wavelengths. Methods. To put constraints on the properties of cometary dust aggregates, we thoroughly investigate the angular and spectral dependencies of intensity and polarization for aggregate particles consisting of identical homogeneous spheres based on a rigorous light-scattering theory. Results. The optimum parameters found through our comprehensive survey are a V 0.6 µm for the radius of aggregates, a m ≈ 0.1 µm for the radius of constituent spheres, n ≈ 1.8-2.0 for the real part of the refractive index, k ≈ 0.4-0.6 for the imaginary part and dm/dλ > ∼ 0 for the spectral gradient of the refractive index. In particular, the best results are obtained for the refractive indices derived from a synthetic mixture of carbonaceous material, magnesium-rich silicate, and iron-bearing sulfide with their abundances simulating the composition of dust in the comet 1P/Halley. Conclusions. Despite the simplicity of our model, these parameters are entirely consistent with our best knowledge of the properties of cometary dust. The common angular and spectral dependencies of intensity and polarization observed for cometary dust are explained with similarities in the average size and element composition of the constituent grains forming dust aggregates. Slight differences in the observed optical data may result from variations in the processing of cometary matter.

show abstract

“…4. Dobrovolsky (1966) postulated that a rapid increase in the solar radiation in the UV or X-ray region can lead to the increase in dissolution of parent molecules situated in the head of a comet. If daughter molecules are much more stable in the solar radiation field than their parent molecules, the total number of the molecules situated in the cometary head will considerably increase.…”

Section: Pioneering Hypothesesmentioning

confidence: 99%

The outbursts of the comet 29P/Schwassmann‐Wachmann 1: A new approach to the old problem

Gronkowski

2014

Astron Nachr

View full text Add to dashboard Cite

As far as outbursts activity is concerned, the 29P/Schwassmann-Wachmann 1 is the exceptional comet. This Centaur object shows quasi-regular flares with periodicities of 50 days (Trigo-Rodriguez et al. 2010). In the introductory part of the presented paper the most well-known hypotheses which try to explain this cometary behaviour are reviewed. The second, actual part of this paper presents the new model for the outburst activity of this comet. The model is based on the idea of Ipatov (2012), according to which there are large cavities below a considerable fraction of the comet's surface containing material under high gas pressure. In favourite conditions the surface layers over the cavities are thrown away and the interior of these cavities is exposed. Consequently, an outburst of the comet's brightness may be observed. The main characteristics of an outburst of this comet, the brightness jump, is calculated. Numerical simulations were carried out for wide range of possible cometary parameters. The obtained results are in good agreement with the observations.

show abstract

Polarimetry of comets: A review

Cited by 26 publications

References 25 publications

Modeling Porous Dust Grains With Ballistic Aggregates. Ii. Light Scattering Properties

Modeling Porous Dust Grains With Ballistic Aggregates. Ii. Light Scattering Properties

Light scattering by cometary dust numerically simulated with aggregate particles consisting of identical spheres

The outbursts of the comet 29P/Schwassmann‐Wachmann 1: A new approach to the old problem

Contact Info

Product

Resources

About