Researchers explain why bands form behind a comet's dust tail

Findings are based on the movement of dust particles in Comet McNaught, one of the brightest comets seen from Earth in the past five decades

Researchers at UCL claim to have finally solved a puzzle that has perplexed the scientific community for year: the phenomenon behind the formation of bands stretching millions of kilometers behind a comet's dust tail.

Researchers state that these characteristic patterns behind a comet's tail are formed due to the charged nature of the dust particles and the role played by the Sun. The study was led by researchers at UCL Mullard Space Science Laboratory (UCL MSSL), and was based on the movement of dust particles in CometC/2006 P1, also known as Comet McNaught. This comet was discovered in August 2006 by astronomer Robert McNaught. When discovered, it was one of the brightest comets seen from Earth in the past five decades.

Throughout January 2007, Comet McNaught was visible across the skies of the Southern Hemisphere, even during the day. Its most unique feature was its highly structured tail, which was formed of multiple distinct dust bands called striations or striae. These striae stretched for over 100 million miles behind the comet.

For years, scientists have been trying to explain the phenomenon behind the breaking up of McNaught's tail in that characteristic manner, but had little success.

Now, scientists from UCL MSSL claim that they have understood the phenomenon. The team used pictures obtained by NASA spacecraft - STEREO and SOHO - to analyse the behaviour of dust particles.

According to them, when the comet approaches near the Sun, intense heat vaporises the frozen gases in the comet's head. This vaporisation releases dust, which moves behind the comet and forms two different types of tails - a plasma tail and a dust tail.

Dust grains released from the comet's head break up into smaller particles, producing long bands and forming striations in the dust tail. Solar winds move the smallest grains in these bands around, thereby altering the tilt of the parts of the bands.

The detailed findings of the study are published in the journal Icarus.