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Press Release ING 2/2000
Date: Friday 28 July 2000 Embargo: For immediate release THE JACOBUS KAPTEYN TELESCOPE OBSERVES THE DEATH OF COMET LINEAR
Nightly observations made since July 23 in different broadband filters with
the 1-m Jacobus Kapteyn Telescope on La Palma, Canary Islands, Spain show
what appears to be the complete disruption of the nucleus of comet LINEAR,
the brightest comet of the year.
Dr. Mark Kidger, Instituto de Astrofísica de Canarias reports from
the Jacobus Kapteyn Telescope: "The central condensation was highly
condensed and showed the typical 'teardrop' form in the evening of July 23rd
and July 24th, although its brightness decreased by a factor of about 3
between the two nights. In the evening of July 25th something very odd was
happening to the comet: the central condensation was seen to be strongly
elongated, with a very flat brightness distribution. The condensation's
brightness faded further and its length increased on the following nights.
On July 27 there was no evidence of any local brightness peaks that would
indicate the presence of sub-nuclei."
In other words, it does not appear to have broken into individual fragments
in the way that Comet Shoemaker-Levy 9 did in 1993. Instead, it has
completely blown apart.
The expansion velocity of the condensation is about 40 m/s, indicating that
it is solid particles and not gas. The gas tail, which virtually disappeared
between July 23rd and 24th, has reformed as an extension of the major axis
of the central condensation.
Comet LINEAR, or C/1999 S4 (LINEAR) as it is called in correct astronomical
nomenclature, is a by-product of the automated LINEAR minor-planet survey.
Discovered nearly as far out as Jupiter last September, this comet passed
114 million kilometres from the Sun on July 26 and only 56 million
kilometres from Earth on July 22. Comet LINEAR is a "new" comet which means
that it is making its very first passage through the inner solar system. The
surfaces of new comets are believed to be covered almost completely by a
very thin, fragile layer of highly volatile ices such as carbon dioxide
intermixed with dust.
When discovered, Comet LINEAR was immediately regarded as a candidate likely
to reach naked eye visibility based on its relative brightness and large
heliocentric distance. New comets though, are notoriously difficult to
predict as far as their light curve behaviour is concerned, particularly
many months in advance.
At present Comet LINEAR is diving southward from the constellation Ursa
Major into Leo. It will be about 20 degrees above the west-northwest horizon
as evening twilight deepens. Although not visible to the naked eye, the
comet will continue to be in northern skies until the second
week of August, when it will dip below the horizon. The observations with
the Jacobus Kapteyn Telescope suggest though that the comet is dying very
quickly and may disappear completely within a few days.
The Jacobus Kapteyn Telescope will continue to observe its disintegration
over the next few nights, hopefully giving new insights into the nature of
comet nuclei and their structure.
The Jacobus Kapteyn Telescope is part of the Isaac Newton Group of
Telescopes (ING). The ING is an establishment of the Particle Physics and
Astronomy Research Council (PPARC) of the United Kingdom and the Nederlandse
Organisatie voor Wetenschappelijk Onderzoek (NWO) of the Netherlands. Apart
from the Jacobus Kapteyn Telescope, the ING also operates the 4.2 metre
William Herschel Telescope and the 2.5 metre Isaac Newton Telescope. The
telescopes are located in the Spanish Observatorio del Roque de Los
Muchachos on La Palma which is operated by the Instituto
de Astrofísica de Canarias (IAC).
PICTURES
Picture credit: Dr. Mark Kidger, Instituto de Astrofísica de
Canarias.
Available formats:
Picture credit: Nik Szymanek and Ian King.
Available formats:
FOR FURTHER INFORMATION PLEASE CONTACT:
Dr. Mark Kidger
Mr. Javier Méndez
More information on ING:
http://www.ing.iac.es/PR/
More information on this news can be found in IAU circular 7467.
Other web sites:
Mark Kidger's comet web pages: http://www.iac.es/galeria/mrk/ |