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In 1995, a new solar observatory was launched. A joint project of ESA and NASA, the Solar and Heliospheric Observatory – SOHO – has been sending home images of our dynamic sun ever since. SOHO was planned to open up a new era of solar observations, dramatically extending our understanding of the star we live with. . . and it delivered.
But no one could have predicted SOHO's other observational triumph: In the last two decades, SOHO has become the greatest comet finder of all time. In August 2015, SOHO is expected to discover its 3000th comet. Prior to the SOHO launch, only a dozen or so comets had ever even been discovered from space, and some 900 had been discovered from the ground since 1761.
"SOHO has a view of about 12 and a half million miles beyond the sun>," said Joe Gurman, the mission scientist for SOHO at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "So we expected it might from time to time see a bright comet near the sun. But nobody dreamed we'd approach 200 a year."
More than just a celebrated bright vision in the night sky, comets can tell scientists a great deal about the place and time where they originated. Comets are essentially a clump of frozen gases mixed with dust. They are often pristine relics that can hold clues about the very formation of our solar system. On the other hand, if they have made previous trips around the sun, they can hold information about the distant reaches of the solar system through which they've traveled. We have a variety of tools to determine what comets are made of from afar. One is to watch how material evaporates off its surface when it comes close to the sun, and here's where SOHO can provide remarkable information.
SOHO is unique in that it is able to spot comets that skim extremely close to the sun, known as sungrazers. One of SOHO's instruments, called a coronagraph, specifically blocks out the bright light of the sun to examine its atmosphere – which is a billion times fainter than the star itself. To this day, SOHO is one of our best sources for views of the giant explosions regularly produced by the sun called coronal mass ejections, or CMEs, which can hurl a million tons of solar particles off into space. This field of view is large enough to see a sungrazing comet as it sling shots around the sun.
(Score: 0) by Anonymous Coward on Monday August 03 2015, @03:06AM
I used to use some of the charged particle data from SOHO back in the 90's.
Kudos Mr. Knackerbracket on this story. We need more like this so that we don't have to listen to the same tired political tripe that gets thrown around here for "discussion". Too bad nobody wants to have any discussion on topics like this.