Mercury moves across the sun

The innermost planet in the solar system will make a perfect bullseye when it crosses the sun on Monday. The event, which began at 7:35 a.m. EST, lasts 5½ hours and will be visible in the eastern United States and Canada, and Central and South America, weather permitting.

How often does this occur? Mercury crosses between Earth and the sun only 13 or 14 times a century. It won’t happen again until 2032, and the next one visible to Americans will take place in 2049. It is not safe to look at the sun directly, so viewers should use telescopes or binoculars with solar filters to follow the tiny dot as it crosses the sun.

Dig deeper: Watch NASA’s broadcast of the transit as seen from the orbiting Solar Dynamics Observatory.