The 1996 Christmas Comet as seen by SOHO. Photo: NASA/ESA

Both amateur and professional astronomers are using the joint European Space Agency/NASA Solar and Heliospheric Observatory (SOHO) to find so-called "sungrazing" comets that pass very close to our Sun.

After its launch in 1995, SOHO was placed at one of the LaGrange points -- the point where the influence of gravity from Earth and the Sun is equal. It is currently located around 1.5 million kilometers from Earth and gets an uninterrupted view of the Sun.

During the first three years of its mission, SOHO's videos and images of the Sun were available only to team members at ESA and NASA centers. But in late 1998, SOHO's realtime videos were posted on the internet to be viewed live by anyone in the world.

"In late 1998 we put SOHO's realtime coronagraph movies online so that anyone with an internet connection could access the data" says Doug Biesecker, a solar physicist at the Goddard Space Flight Center (GSFC) in Maryland and SOHO's top comet finder with 47 confirmed sightings.

In a rare celestial spectacle, two comets were observed plunging into the Sun's atmosphere in close succession on June 1 and 2, 1998. Photo: NASA/ESA

"Over a three year period before that time we had found 58 comets near the Sun in SOHO images. Now the total is up to nearly 170. Amateur astronomers watching coronagraph movies on the web are responsible for nearly all of the new finds this year. They're keeping me very busy!"

A coronagraph is a disk-like device that blocks out the intense light of the Sun so that only the surrounding corona is visible. This enables the spacecraft instruments able to see planets, stars, and comets in its field of view.

After only five years, SOHO has confirmed the findings of 146 comets, but that number could be as high as 176. Scientists are trying to confirm the other 30 sightings.

Sungrazing comets are believed to be parts of larger and older comets that have broken up while traveling close to the Sun in the past. As they near the Sun, they brighten briefly then disappear behind the Sun.