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Astronomers at the University of Hawaii, led by Dr Yanga Fern�ndez, have discovered 18 new fragments trailing behind comet du Toit-Neujmin-Delporte illustrating once more that comets are the fragile snowballs of the Solar System. Fern�ndez and colleages decided to look for the presence of fragments when they learnt that a single companion to the comet had been found. The newly discovered fragments form a string of pieces extending over a distance of a million kilometres behind the comet's icy nucleus and vary from a few hundred to a few tens of metres in size.
The researchers believe that the comet may have broken up during its last passage close to the Sun in 1996 when it was observed to be unusually bright. Comets are thought to consist of ice and dust grains and are often likened to dirty snowballs. When the solid icy nucleus of a comet approaches the Sun to within the orbit of Jupiter heating turns its ice into gas and a tail millions of kilometres long forms. Sometimes comets are observed to become much brighter since they are producing more gas. One reason that such outbursts might occur is if a pocket rich in carbon dioxide ice, which could turn to gas explosively, is uncovered . Such an explosion may have caused the break-up of du Toit-Neujmin-Delporte and would indicate that the nucleus is very weak. Perhaps the best known break-up of a comet was that of Shoemaker-Levy 9 that was eventually to collide with Jupiter in 1994. The icy nucleus of that comet was broken to pieces by differences in the force of gravity as it passed by Jupiter since the gravity of the giant planet pulled harder on the near-side of the nucleus than the other. The force that broke up Shoemaker-Levy 9 has been estimated to have been less than that needed to pick up a feather from the Earth's surface.
More info: University of Hawaii
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