Photometrical analysis of the Neck-Line Structure of Comet Halley
Abstract
In this paper we apply the quantitative analysis of Neck-Line Structures (NLS; M. Fulle and G. Sedmak, Icarus 74, 383-398 (1988) ) to the dust streamer and the real antitail which were detected in images of Comet Halley during April, May, and June, 1986 ( Z. Sekanina, S. M. Larson, G. Emerson, E. F. Helin, and R. E. Schmidt, Astron. Astrophys. 187, 645-649 (1987) ), and which were best explained by the NLS model ( M. Fulle, Astron. Astrophys. 181, L13-L14 (1987) ). The results concern the dust size distribution at very large sizes, the size-dependent dust ejection velocity from the inner coma. and the anisotropy of dust ejection. All the results are related to the time interval 1986, Jan 10-18. The size distribution which best fits the NLS isophotes is characterized by a power index u ≈ -4.0 for sizes between 0.2 and 2mm, and u ≈ -0.4 for sizes between 2 and 10 mm. Therefore we confirm the strong excess of large dust suggested by J. A. M. McDonnell et al. ( Astron. Astrophys. 187, 719-741 (1987) ) to explain the Giotto data, although these authors obtained a value u ≈ -3.0 for sizes between 0.2 and 10 mm on 1986, Mar 14. These differences of the u values are in agreement with the results of M. Fulle, C. Barbieri, and G. Cremonese ( Astron. Astrophys. 201, 362-372 (1988) ), which showed large variations of the size distribution between January and March. The dust ejection velocity can be expressed by v = 0.20 × (1 - μ) 1/7 ( km sec-1), where 1 - μ is the ratio between the solar radiation pressure force and the gravitational force, in agreement with the results obtained for Comet Bennett ( M. Fulle and G. Sedmak, Icarus 74, 383-398 (1988) ).
- Publication:
-
Icarus
- Pub Date:
- August 1989
- DOI:
- 10.1016/0019-1035(89)90138-3
- Bibcode:
- 1989Icar...80..267C
- Keywords:
-
- Astronomical Photometry;
- Cometary Atmospheres;
- Halley'S Comet;
- Astronomical Models;
- Coma;
- Giotto Mission;
- Gravitational Fields;
- Interplanetary Dust;
- Radiation Pressure;
- COMETS;
- HALLEY;
- PHOTOMETRY;
- DUST;
- SIZE;
- DISTRIBUTION;
- EJECTION;
- MODELS;
- VELOCITY;
- ANISOTROPY;
- STRUCTURE;
- IMAGERY;
- COMET TAILS;
- BENNETT;
- GEOMETRY;
- THEORETICAL STUDIES;
- CALCULATIONS