Imaging Photometry and Color of Comet Shoemaker–Levy 9

Chernova, G. P.; Jockers, K.; Kiselev, N. N.

doi:10.1006/icar.1996.0070

Cited by 6 publications

(7 citation statements)

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“…• Within the 4000-7000Å window, the polarization increases with wavelength, which is the so-called polarization color effect (e.g., Chernova et al 1996;Levasseur-Regourd & Hadancik 2001).…”

Section: Cometary Dustmentioning

confidence: 99%

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

Shen

Draine

Johnson

2009

ApJ

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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.

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Section: Cometary Dustmentioning

confidence: 99%

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

Shen

Draine

Johnson

2009

ApJ

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“…1). Comet S -L 9 was observed through two successive solar oppositions and no eastward dust features were detected Chernova et al, 1996). Prior studies ofS-L 9 often imply or conclude that the fragments were relatively dormant due to the absence of any eastward dust features (e.g.…”

Section: Sekaninamentioning

confidence: 99%

“…Prior studies ofS-L 9 often imply or conclude that the fragments were relatively dormant due to the absence of any eastward dust features (e.g. Sekanina et al, 1994;Chernova et al, 1996;Sekanina, 1996a). However this conclusion is premature since the observed dust tail orientations were consistent with both the active and the dormant comet hypotheses.…”

Section: Sekaninamentioning

confidence: 99%

“…_ 1997 Elsevier Science Ltd, Ever since the discovery of comet Shoemaker Levy 9 (S L 9) in the spring of 1993 there has been an ongoing debate regarding its activity Chernova et al, 1996;Hahn et al, 1996;Rettig et al, 1996b;Sekanina, 1996a). This point is of no minor consequence, for in order to correctly understand the 1993-1994 observations of the S L9 dust comae and tails it is necessary to know whether one was viewing recent and possibly ongoing dust emission, or perhaps more "ancient" dust emis-…”

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confidence: 99%

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Comet Shoemaker-Levy 9: an active comet

Rettig

Hahn

1997

Planetary and Space Science

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Rather, the tail orien, "-Igtions simply place constraints on the dust production /rj!__te for grains smaller than _ 5ym. All the availabcle _idencc points to S L 9 as having been an active, dust--;ipr°ducing comet. Synthetic images of an active comet±_r¢ fitted to Hubble Space Telescope images of t_l_-? S-L 9 fragment K, and its grain size and outflow velocity -izIisfi'qb-titions are extractediTl_seTq_diggs show that the appearance of the dust coma was dominated by Iarge grains having radii between _ 30 i_m and _ 3 mm_ produced at a rate of M._22kgs -_, and ejected at-; outflow velocities of _0.

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“…The pre-impact images of SL9 were obtained at several observatories: e.g., Chernova et al (1995) with the ESO 1-m; Cochran et al (1995) at McDonald;Colas et al (1995) at Pic-du-Midi; Jewitt (1995a) at the Mauna Kea telescopes; Scotti et al (1994) at the Spacewatch station; Stiiwe et al (1995) with the ESO-NTT; Trilling et al (1995) at Calar-Alto; Weaver et al (1994Weaver et al ( , 1995 with the HST; R. M. West et al (1995) with several ESO telescopes. Tancredi & Lindgren (1994) have reported a negative search for comets in the vicinity of Jupiter undertaken at ESO in March-April 1992, i.e., one year before the discovery of SL9 and several months before its disruption by Jupiter.…”

Section: Pre-impact Observationsmentioning

confidence: 99%

Observational constraints on the composition and nature of comet D/Shoemaker-Levy 9

Crovisier¹

1996

International Astronomical Union Colloquium

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What did the break-up of comet Shoemaker-Levy 9 (SL9) and its subsequent impact on Jupiter teach us about the nature and constitution of this comet? The break-up of the comet apparently triggered activity of the fragments. Although a dust coma was continuously present around the fragments that orbited Jupiter, spectroscopic observations did not reveal any sign of gas. The impact itself was so energetic that most molecules of the impactor were dissociated and that any chemical memory was lost. Ultraviolet and visible spectroscopy of the impact sites revealed emission lines from several atoms, giving potential information on elemental abundances. However, the fact that both neutral and ionized atoms are emitting, and that both fundamental and inter-system lines are present, suggest that the medium is out-of-equilibrium and that emitting mechanisms other than simple resonance fluorescence are at work. Ultraviolet, infrared, and radio spectroscopy revealed lines of several molecular species, in emission and/or absorption, that are not normally present in Jupiter's upper atmosphere. In the visible, dark spots due to aerosols developed at the impact sites. It is not clear at the present time which part of this material is coming from preserved impactor material, from the recombination of the dissociated impactor material, from reactions between the impactor's and Jupiter's material, or from material coming from the lower layers of Jupiter's atmosphere. Realistic modelling of the impacts and of the following chemical reactions will be necessary to address all these issues. In this chapter, we will review the observational clues to the composition and structure of SL9 in the context of our knowledge of the composition and structure of comets and asteroids.

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Imaging Photometry and Color of Comet Shoemaker–Levy 9

Cited by 6 publications

References 0 publications

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

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

Comet Shoemaker-Levy 9: an active comet

Observational constraints on the composition and nature of comet D/Shoemaker-Levy 9

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