April 24, 2003
(PLANETQUEST) -- An upcoming astronomical event will provide a rare opportunity for amateurs to observe a technique scientists are using to search for planets around stars. On May 7, Mercury will pass in front of the Sun, creating a tiny eclipse called a transit.
This event, visible from Europe, Africa and Asia and parts of North America, will provide a close-up example of the "transit method," one of the techniques scientists are using to detect or confirm the existence of planets around other stars. The transit method involves measuring the slight decrease in light from a star when a planet passes across its face. (For more about this planet-finding technique, see Science - Finding Planets.)
The disk of Mercury is very small and will be difficult to see. Observation of the event requires being in the right location (see map) and using a telescope with special protection. It is dangerous to observe the Sun directly; the only completely safe approach is to project the image onto a sheet of paper.
The Mercury transit, which occurs once every seven years, provides a prelude to an even more important celestial event next year. On June 8, 2004, the larger planet Venus will pass in front of the Sun, and will be easily observable from the same continents
If you aren't in the right place to observe the Mercury event directly, you can watch it virtually via one of the the webcams that will transmit live images on the Internet. See "Find out more" (upper right) for links to webcams, and a list of sites that provide comprehensive information on observing the Mercury transit.
