Lockheed Martin Scientists Make First-Ever Observations Of Comet’s Demise Deep Inside Solar Atmosphere

As a comet the size of an aircraft carrier approached the Sun on July 4, 2011, Lockheed Martin scientists readied the instruments they built for NASA’s Solar Dynamics Observatory (SDO) and the two NASA Solar-Terrestrial Relations Observatories (STEREO) to watch its passage across the solar disk  What they witnessed were the first-ever observations of a comet’s demise deep inside the atmosphere of the Sun.

Using observations from the Atmospheric Imaging Assembly (AIA) instrument on SDO, the comet was first seen just off the limb of the Sun, travelling at nearly 400 miles per second and was tracked for 20 minutes until it disintegrated and evaporated in the low solar corona, about 62,000 miles above the solar surface.

Look for the comet as it enters from the right at mid-screen and watch until it disappears.

Lockheed Martin solar physicist Dr. Karel Schrijver, who was the lead author of a paper reporting the observations and analysis in the journal Science, describes the discovery:

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 as it continued to fragment in the intense glow from the Sun’s surface. 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."

During its 15 years of observations, SOHO has observed more than 2000 comets as they approached the Sun. The population of these Sun-grazing comets is dominated by the Kreutz group, whose members orbit to within one to two solar radii from the solar surface (photosphere) every 500 to 1000 years. More than 1400 of the comets seen by SOHO are members of the Kreutz group, making it the largest known group of comets, likely originating from the breakup of a progenitor body as recently as 2500 years ago. Only the largest of the Kreutz group comets, with diameters of up to about 330 feet have survived perihelion – their closest approach to the Sun.

Comet death into the Sun

Click image above for a larger view

The doomed comet is seen approaching the Sun during a July 4, 2011 death dive. A view from the ESA/NASA Solar and Heliospheric Observatory (SOHO) appears in the lower left. The main image is a composite view of the Sun from SDO that shows gas spewing from the comet at temperatures of 1 million Kelvin as it descends into the solar corona to the point of destruction. Insets show the contrast-enhanced emission from the comet's tail six times during the last ten minutes of the comet's existence.