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Pic du Midi Observatory Image of Comet Hale-Bopp


Observers: Francois Colas, Jean Lecacheux, Sylvie Jancart, Luc Henrard
Location: Pic du Midi Observatory, France
Date: April 29, 1997 20:35 UT

The sodium tail confirmed by the Pic-du-Midi team. April 29

The newly discovered tail of neutral sodium atoms (see IAUC 6631 and Web pages made by the Isaac Newton Group, Canary Islands) is a major new feature, never seen in bright comets in the past, excepted during some hours in the sungrazing ones, but under very extreme temperature conditions that comet Hale-Bopp does not experience. We used a 50-mm F/1.4 Pentax photographic objective , a narrow band interference filter and a HiSiS-44 CCD camera (equipped with a Kodak 1536x1024 chip) to observe the new sodium tail of the comet. The field of view was not less than 15x10 degrees. The bandpass centered on the yellow D line doublet was 2.8 nm wide. The present image is a 32 minutes integration near 20 h 35 UT on April 29th evening. North is up. The sodium tail is the narrow 8 degrees long feature near p.a. 55 degrees. Do not confuse it with the ion tail, of which general orientation is roughly similar : in fact no ion emission seems exist in our filter bandpass. The well marked curvature of the neutral sodium tail in this image appears important to understand the formation mechanism .

Contact: Francois Colas (

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