The current sheet causes all the disruptions in the dust tail following the changes in the magnetic field.

In January 2007, the twin STEREO satellites captured the first ever satellite images of Comet McNaught. STEREO-B was the first to begin its operation. First few minutes of its observation did cause some panic among the mission’s team as they got pearly white, feathery smear instead of the vast star-field they expected. However, they soon realized that there was nothing wrong with the telescope and they were actually looking at a really bright object. STEREO-A confirmed that by making similar observations a few hours later. The scientific name of the comet is Comet C/2006 C1 but it became famous by the name of the astronomer who discovered it in 2006, Robert McNaught. It was so bright that it was visible to the naked eye across the sky of Southern Hemisphere for the entire month of January 2007.

Comet McNaught belongs to a rare group of comets who are commonly known as Great Comets due to their intensive brightness. Comet C/2006 C1 was a bit different from its companions due to its highly structured tail. It is made up of several distinct bands of dust called Striae (Striations). They stretched more than 100 million miles behind the comet. Karl Battams, an Astrophysicist at the Naval Research Laboratory in Washington D.C who took part in the development of STEREO spacecraft, praised the beauty of this celestial object in the following words:

“McNaught was a huge deal when it came because it was so ridiculously bright and beautiful in the sky. It had these striae — dusty fingers that extended across a huge expanse of the sky. Structurally, it’s one of the most beautiful comets we’ve seen for decades.”

Despite all the interest, scientists couldn’t figure out a logical explanation for this comet tail. A joint mission of the European Space Agency and NASA, Solar and Heliospheric Observatory (SOHO), kept a continuous eye on the McNaught as it flew by the sun. Astronomers hoped that the images captured by this mission will help them to unveil the mystery of this amazing comet tail. Having said that, no significant development was observed until recently when Oliver Price, a Planetary Science Ph.D. student at the Mullard Space Science Laboratory of the University College London, came up with a new image-processing technique that could help researchers to make use of the priceless data. In addition to that, the study also made an unusual revelation about the effects of the Sun on the comet’s dust.

Scientists believe that comets might contain important information about the early history of our solar system in their constituting materials. Whenever a comet goes near the sun, these clues are unlocked as the heat from the star of our solar system vaporize the frozen gases to release the stored dust particles. This gives two distinct tails to the comet (a dust tail and an ion tail formed by the solar wind). The understanding of the behavior of the dust tail can give some real insights about the processes that led to the formation of asteroids, moons, and even planets billions of years ago.

McNaught is considered an ideal candidate for this kind of a study due to its brightness and high dust production. Price mentioned that he wanted to investigate the reason why the direction of the dust tail changed as scientists were unable to figure out an explanation for that. Previous studies indicated that the dust in McNaught’s tail is too heavy to be pushed around by the ion tail. Although researchers were aware of this fact, it was proving difficult to find the exact reason behind this mystery as the comet was moving rapidly in and out of the view of SOHO and STEREO. Price referred to that by saying,

“We got really good data sets with this comet, but they were from different cameras on different spacecraft, which are all in different places. I was looking for a way to bring it all together to get a complete picture of what’s happening in the tail.”

In order to counter that, he proposed an image-processing technique which made use of all the data from different spacecraft. Consequently, Price was able to develop a temporal map which covered information from all the images taken at any given moment. This allowed him to follow the movement of the dust tail at all instances as he could observe the striations form over time. The videos he made clearly showed how the dust fragments left the comet’s head to form long striae. He discovered that the current sheet was causing all the disruptions in the dust tail due to the changes in the magnetic field. Geraint Jones, a Planetary Scientist at the University of London, talked about this finding and said,

“It’s like the striation’s feathers are ruffled when it crosses the current sheet. If you picture a wing with lots of feathers, as the wing crosses the sheet, lighter ends of the feathers get bent out of shape. For us, this is strong evidence that the dust is electrically charged, and that the solar wind is affecting the motion of that dust.”