PARIS, May 6: Astronomers in many parts of the world will be in for a rare treat on Wednesday when Mercury will transit across the face of the Sun, appearing as a tiny black dot crawling across the solar surface.

The five-hour event can be seen its entirety from most of Europe, Africa and Asia, while people living in Japan, parts of Australia and the northeastern parts of North and South America will get a glimpse of it, after sunrise or before sunset.

The “transit” occurs when the Sun, Mercury and Earth are in alignment, an event that will happen only 14 times this century.

The last time was in November 1999; the next will take place on November 8, 2006, and will favour observers on the Pacific rim.

Precautions are needed to observe this event. Watching the Sun directly, without a proper solar filter, can permanently damage one’s eyesight.

Mercury is a rocky planet about a third the size of Earth.—AFP