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Observations of Comet Halley at ESO Continue

26 lutego 1986

23 February was the last morning when Comet Halley could be seen in a dark sky. During the next two weeks, the moonshine will hamper further detailed observations of the incredibly complicated tail structure which was recently detected at the European Southern Observatory on La Silla.

23 February was the last morning when Comet Halley could be seen in a dark sky. During the next two weeks, the moonshine will hamper further detailed observations of the incredibly complicated tail structure which was recently detected at the European Southern Observatory on La Silla.

As a matter of fact, whereas normal photographic equipment has only been able to show two tails, four tails were detected with special equipment at La Silla already last Wednesday, 19 February. Seven tails were identified on Thursday, 20 February and an eighth tail was seen on Saturday, 22 February.

These observations were made with two telescopes, one belonging to the Ruhr University of Bochum, German Federal Republic and the other, which was specially designed for observations of Halley, to ESO.

ESO scientists believe that the additional tails, which point to north and north-east consist of dust which was released from the 6 km nucleus some days ago. The additional tails have a very red colour, indicating that they shine by reflected sunlight. The two major tails towards west are blue and must therefore consist of ions, that is electrically charged particles which are pushed away by the solar wind.

Observations on Sunday morning (23 February) at La Silla indicated that important changes are taking place in the comet. Four tails could be easily recognized even through small telescopes and the appearance of the comet to the naked eye was definitely more impressive than on Saturday morning.

The observations from La Silla have been transmitted daily to the Central Bureau of the International Astronomical Union in Cambridge, Mass., USA. The ESO scientists learned from the Bureau yesterday that, due to unfortunate cloudy weather in most other parts of the world, observations at La Silla during the past nine mornings are among the only ones available which provide full coverage of the important post-perihelion activities of Comet Halley. In particular, the Bureau informed that accurate positions have only been registered from ESO so far and that therefore the navigation of the five spacecrafts on way to Halley has been highly dependent on the ESO data.

Although this passage of Halley will be the faintest one in the 2000 years this famous object has been observed, it appears that the comet is putting on an unexpected display of tails, for the benefit of the many millions of people who are now eagerly awaiting Comet Halley. In the southern hemisphere the best time to see it will be in about 14 days from now, at the time of the New Moon, when the moonlight no longer interferes.

Kontakt

Richard West
ESO
Garching, Germany
Tel.: +49 89 3200 6276
E-mail: information@eso.org

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