The comet flies across the surface of the sun   On July 6, 2011, the last few seconds of a comet\'s dive into the sun, when it evaporated in the heat above the star\'s surface, were caught on camera for the first time. Comet-watchers were astonished. No one had expected to be able to see the final moment, even with today\'s best orbiting space observatories.
\'Comets are usually too dim to be seen in the glare of the Sun’s light,” says Dean Pesnell project scientist for Nasa\'s orbiting Solar Dynamics Observatory. \'We’ve been telling people we’d never see one in SDO data.\'
But an ultrabright comet, from a group known as the Kreutz comets, overturned everybody\'s ideas.
The comet can was seen moving over the right side of the Sun, disappearing 20 minutes later as it evaporates in the searing heat.
Watching the comet’s death provides a new way to estimate the comet’s size.
The comet turns out to be somewhere between 150 and 300 feet long and to have about as much mass as an aircraft carrier.
\'Of course, it’s doing something very different than what aircraft carriers do,\' says Karel Schrijver, a solar scientist at Lockheed Martin in Palo Alto.
\'It was moving along at almost 400 miles per second through the intense heat of the Sun -- and was literally being evaporated away.\'
Scientists at the Lockheed Martin Solar and Astrophysics Laboratory at the Advanced Technology Center in Palo Alto, discovered the comet on July 4, 2011, by using the Large Angle and Spectrometric Coronagraph on the ESA/Nasa Solar and Heliospheric Observatory (SOHO).
It was the SOHO discovery that alerted Lockheed Martin scientists to watch data from the Solar Dynamics Observatory\'s cameras for the comet\'s likely transit across the face of the Sun.
\'This unprecedented passage of a comet through the solar atmosphere in view of our AIA cameras presented us with a remarkable opportunity,\' said Dr. Karel Schrijver, lead author of the Science paper.
\'As we witnessed this comet evaporate as it traversed a known amount of space over a specific period of time, we were able to work backward to estimate its mass just before it reached the Sun. We’ve been able to bracket its size as between 150 and 300 feet long, with a greater likelihood that it lies at the upper end of that range.
And it most likely weighed in at as much as 70,000 tons, giving it about the weight of an aircraft carrier, when it first became visible to AIA.\'
As the comet streaked into the solar atmosphere it had already fractured into many large pieces ranging in size from 30 to 150 feet.
The pieces were embedded in the nebulous envelope made up of ice, dust, and gas called the coma, surrounding the comet’s nucleus.
The coma was estimated to be about 800 miles across, followed by a glowing tail approximately 10,000 miles long.
The tail was seen pulsing from dim to bright to dim again during the journey across the Sun, which suggests that there was further breakup of the individual chunks of comet
Eventually, the comet evaporated completely.
\'I think the light pulses in the tail were one of the most interesting things we witnessed,\' said Schrijver.
\'The comet’s tail gets brighter by as much as four times every minute or two. The comet seems first to put a lot of material into that tail, then less, and then the pattern repeats.
\'Only because of these pulses can we measure how fast the tail falls behind the comet as its gases collide with those in the Sun’s atmosphere. And that, in turn, helps us measure the comet’s weight.\'