LEAD: With a bit of serendipity that comes often comes from science research, a NASA satellite played a key role in discovering the 3,000th comet.
1. Before the launch in 1995 of the NASA and European Space Agency's Solar and Heliospheric Observatory satellite (known as SOHO) there were about 900 known comets. After 20 years SOHO has just spotted its 3000th comet.
2. SOHO's ability to spot comets turns out to be an unplanned and unexpected benefit.
3. SOHO's main job is to study the sun, not comets. But citizen scientists and astronomers from around the world combing through SOHO data have greatly expanded our knowledge about comets.
4. An amateur astronomer in Thailand spotted number 3,000.
TAG: Citizen scientists, including two 13-year-olds, have found 95 percent of SOHO comets.