Comet LINEAR: Going, going...but not quite gone
ISAAC NEWTON GROUP OF TELESCOPES NEWS RELEASE
Posted: August 5, 2000
Having previously appeared completely normal, on the night of July 25th the comet was seen to undergo a rapid change. The initially compact comet nucleus evolved into a fuzzy, extended and much fainter object. This caused much speculation as to what the reason for the disruption of the comet might be. Further observations with the telescopes of the Isaac Newton Group at the Roque de los Muchachos Observatory, La Palma, Spain as well as telescopes elsewhere have confirmed the initial discovery and provided new insight into what the reason for the comet disruption could be: the evaporation of all the ice in the nucleus.
Cometary nuclei are a mixture of solid lumps of material of various sizes, held together by a cement of ices. When comets pass close to the Sun during their journey across the solar system the icy elements (mainly water ice and carbon monoxide ice) sublime, leaving loose material behind that forms the dust tail of the comet, while the sublimed ice forms its gas tails. As a result of this process, or due to the strong gravitational pull from a planet such as Jupiter, or from the Sun, a comet nucleus may sometimes split into two or more fragments. What was seen in the case of Comet LINEAR, however, was different.
From analysis of the images that lay out the recent sequence of events for Comet LINEAR, Dr. Mark Kidger from the Spanish Instituto de Astrofisica de Canarias concludes that this small comet probably ran out of ice altogether, leaving behind a loose conglomerate of particles that are now gradually dispersing into space. This model fits the observations well, as measurements have shown that the activity of the comet had been declining for several weeks as ice gradually sublimed away. During the comet's closest approach to the Sun, a burst of activity was recorded. Then, when all the ice was exhausted and nothing was holding together the solids, the nucleus began to fall apart.
Comet LINEAR has maybe not been a spectacular night-time sight for most people, but for astronomers it presents an important and unique event of what can be described as the death of a comet.
The Isaac Newton Group of telescopes (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. The ING operates the 4.2 metre William Herschel Telescope, the 2.5 metre Isaac Newton Telescope, and the 1.0 metre Jacobus Kapteyn Telescope. The telescopes are located in the Spanish Observatorio del Roque de Los Muchachos on La Palma which is operated by the Instituto de Astrofisica de Canarias (IAC).