eso8607 — Foto de imprensa
Comet Halley's Tails
6 de Março de 1986
This spectacular image of Comet Halley, rising above the eastern horizon, was obtained at the La Silla observatory during the morning of February 22. It was made by superposing 6 exposures (total 9 min.) with the wide-field CCD camera which was specially designed for the study of Comet Halley. The image measures 5.5 x 9 degrees across and covers the 500 - 1100 nm spectral region (green near infrared). Each pixel (image element) measures 31 x 31 arc-seconds.
Comet Halley's multiple tails (22 February)
On this date the comet was 99 million kilometres from the sun and 209 million kilometres from the earth. At least seven tails can be discerned. Two ion tails point straight up (towards west). The other tails, pointing toward north and northeast, are rather red and are thought to consist mainly of dust. It was released from the small nucleus which is invisible in this picture. The length of the ion tail is at least 6 degrees, or 22 million kilometres. The very complex tail system was discovered at ESO a few days earlier.
The bright stars at the top are Alpha and Beta Capricorni (the vertical lines are caused by saturation of the detector).
Comet Halley develops 15-degree tail (27 February)
Three days past full moon, when it was difficult to see Comet Halley in the bright sky, this picture was obtained on 27 February at the ESO La Silla Observatory by means of a special wide-field camera. It shows the famous comet as imaged by a CCD detector through an optical filter that suppresses the moonlight in order to make the comet's 15 degree tail visible.
The image was obtained in violet light at 426 nm (half-width 7 nm), centered on the spectral emission of CO+ ions. It therefore shows the distribution of these ions in the tail, as they are pushed away from the comet by the solar wind. Near the comet head several streamers are visible - further upstream the tail broadens and becomes less dense as the ions disperse in interplanetary space. On this date, Comet Halley was at a distance of 196 million kilometres from earth and the length of the tail was at least 50 million kilometres.
Observations continue at ESO to study the evolution of the tail.
Comet Halley's CO+ tails (3 - 5 March)
These images of Comet Halley's ion tails were obtained on 3, 4 and 5 March by means of the Wide-Field CCD camera, specially installed at La Silla for the purpose of monitoring the spectral emission of CO+ ions in the tail of this comet. The images were obtained through a narrow filter, centred at 426 nm in the violet region of the spectrum.
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