کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10701388 | 1021129 | 2013 | 26 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Keck and VLT AO observations and models of the uranian rings during the 2007 ring plane crossings
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
علوم فضا و نجوم
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چکیده انگلیسی
We present observations of the uranian ring system at a wavelength of 2.2 μm, taken between 2003 and 2008 with NIRC2 on the W.M. Keck telescope in Hawaii, and on 15-17 August 2007 with NaCo on the Very Large Telescope (VLT) in Chile. Of particular interest are the data taken around the time of the uranian ring plane crossing with Earth on 16 August 2007, and with the Sun (equinox) on 7 December 2007. We model the data at the different viewing aspects with a Monte Carlo model to determine: (1) the normal optical depth Ï0, the location, and the radial extent of the main rings, and (2) the parameter AÏ0 (A is the particle geometric albedo), the location, and the radial plus vertical extent of the dusty rings. Our main conclusions are: (i) The brightness of the â ring is significantly enhanced at small phase and ring inclination angles; we suggest this extreme opposition effect to probably be dominated by a reduction in interparticle shadowing. (ii) A broad sheet of dust particles extends inwards from the λ ring almost to the planet itself. This dust sheet has a vertical extent of â¼140 km, and AÏ0 = 2.2 Ã 10â6. (iii) The dusty rings between ring 4 and the α ring and between the α and β rings are vertically extended with a thickness of â¼300 km. (iv) The ζ ring extends from â¼41,350 km almost all the way inwards to the planet. The main ζ ring, centered at â¼39,500 km from the planet, is characterized by AÏ0 = 3.7 Ã 10â6; this parameter decreases closer to the planet. The ζ ring has a full vertical extent of order 800-900 km, with a pronounced density enhancement in the mid-plane. (v) The ηc ring is optically thin and less than several tens of km in the vertical direction. This ring may be composed of macroscopic material, surrounded by clumps of dust.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Icarus - Volume 226, Issue 2, NovemberâDecember 2013, Pages 1399-1424
Journal: Icarus - Volume 226, Issue 2, NovemberâDecember 2013, Pages 1399-1424
نویسندگان
Imke de Pater, David E. Dunn, Daphne M. Stam, Mark R. Showalter, Heidi B. Hammel, Michiel Min, Markus Hartung, Seran G. Gibbard, Marcos A. van Dam, Keith Matthews,