The Dust Environment of Comet Austin 1990 V

Details The Dust Environment of Comet Austin 1990 V The Dust Environment of Comet Austin 1990 V

May 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...272..634f&link_type=abstract

Astronomy and Astrophysics, vol. 272, 634-650. Article.

Astronomy and Astrophysics

Astrophysics

16

Comets, Dust Tails, Comets, Austin, 1990V, Dust, Comet Tail, Earth-Based Observations, Monte Carlo Method, Particles, Grains, Ejecta, Velocity, Power, Size, Distribution, Photometry, Models, Data, Calculations, Parameters, Mass, Comparison, Ejection, Comet Nuclei, Comae, Fragmentation, Meteoroids

Scientific paper

We analyse 12 Schmidt plates concerning the dust tail of comet Austin 1990V taken at the Observatories of Catania, Cerro Tololo, ESO and Siding Spring during May and June, 1990. The absolute calibration of the images was performed by means of some standard fields of the Guide Star Photometric Catalogue I (Lasker et al. 1988) detected on the same plates containing the comet images. At the beginning of June the predicted Neck-Line Structure (Fulle & Pansecehi 1990) was detected and well observed as a streamer superimposed on the dust tail and an opposite sunward spike. We apply the inverse Monte- Carlo dust tail model (Fulle 1989) to two different sets of images, which provide results in reciprocal close agreement even if in the two sets the dust tail has a very different shape. We analyse dust grains of diameters between 10 μm and 10 cm ejected during the time interval -160 d < t < +60 d (days related to perihelion). The ejection velocity of millimeter-sized dust grains reaches its maximum value of 0.1 km s-1 at t = +10 d. The mass loss rate reaches a broad maximum of at least 3 l07 g s-1 a few days before perihelion. The power index of the time-averaged size distribution is -3.0±0.2. Strongly anisotropic dust ejections from the nucleus surface are incompatible with the observed shape of the dust tail. Further, the results of the photometry of the Neck-Line concerning the size dependence of the dust velocity and the observed length of the sunward spike indicate that the classical power index of the size dependence of the dust velocity u = -½ cannot account for all the observations. On the contrary, significantly higher index, u = -⅙, allows to reproduce very closely all the available data of the C/1990V dust tail. Also the size distribution and the mass loss rate given by the Neck- Line photometry agree with the results of the inverse Monte-Carlo model, thus supplying the first example of complete agreement between the two models. Although C/1990V was a new comet, characterized by a hyperbolic orbit, it injected in the Solar System a large mass of meteoroids in bound orbits, at least 10% of the total observed dust mass [(1.7±0.2)1014 g] produced by the comet during its passage in the neighborhood of the Sun.

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