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Comets in the farthest reaches of the Solar System may break-up many times suggests Dr. Zdenek Sekanina, senior research scientist at NASA JPL, in the Astrophysical Journal. Previously scientists had assumed that comets break-apart rarely and only when closer to the Sun due to either explosive outbursts of gas or the tidal forces exerted by the planets and the Sun. Sekanina, however, has examined a group of comets known as sungrazers and found that many of these comets arrive at the Sun in clusters and on parallel paths. Because comets are dirty snowballs, Sekanina argues that small fragments amongst the clusters would have been destroyed if they had come so close to the Sun on a previous trip. He concludes that the parents of these tiny sungrazers must have broken up after their previous encounter with the Sun and continued to break up far from the Sun on their journey through the solar system.
"Astronomers never before realized that there could be a fairly orderly pattern in breaking up, so that one comet cascades into large families of smaller comets, and that this process could be an important part of a comet's natural life cycle," Sekanina said. Sungrazers are not the only comets that can break up far from the Sun. Sekanina points to new observations of comet 57P/du Toit-Neujmin-Delporte, whose fragmentation has led to the formation of a similar, though less prominent, highway of tiny comets. All fragments separated from the comet beyond the orbit of Mars.
Images taken by the European Space Agency's and NASA's Solar and Heliospheric Observatory have shown that there are many tiny sungrazing comets. SOHO has so far allowed more than 500 new comets to be identified. Sekanina estimates that currently there may be as many as 200,000 sungrazer comets the same size of the ones the spacecraft has detected.
More info: SOHO Comet Movie
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