An observatory launched into space 15 years ago to observe the Sun has this week discovered its 2,000th comet. It was spotted on an image taken by the satellite SOHO on December 26 by Michal Kusiak, a student at Nicolas Copernicus’s old Jagiellonian University at Krakow, Poland.
SOHO, short for Solar and Heliospheric Observatory, was designed to observe our home star with an array of cameras for NASA and the European Space Agency.
But amateur astronomers swiftly realised that images posted by NASA on the SOHO website were a fertile hunting ground for icy visitors from the depths of space.
Many comets have extremely elongated orbits that bring them swinging close by the Sun, brightening as they do so and often developing long tails of gas and dust.
SOHO’s LASCO, or Large Angle and Spectrometric Coronagraph, cameras are particularly suitable for finding new comets as they have a wide angle of view. They are designed to observe the Sun’s atmosphere and space weather, with a disk blotting out the intensely bright Sun itself.
More than 70 amateur astronomers around the world have discovered comets in the archive of SOHO images available online. Michal Kusiak himself has found more than 100.
Joe Gurman, SOHO scientist at NASA’s Goddard Space Flight Centre in Maryland, said: “Since it launched on December 2, 1995 to observe the sun, SOHO has more than doubled the number of comets for which orbits have been determined over the last 300 years.”
Karl Battams, who runs the SOHO comet-sighting website, said: “Now we know there are far more comets in the inner solar system than we were previously aware of, and that can tell us a lot about where such things come from and how they’re formed originally and break up. We can tell that a lot of these comets all have a common origin.”
Scientists believe that 85 per cent of the comets are from one monster comet that broke up many hundreds of years ago. They are known as Kreutz sungrazers.
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