What's New: November 2019

Transit of Mercury

The planet Mercury – the innermost planet – has an orbit around the Sun interior to that of Earth. Since Mercury travels faster around the Sun than our planet, there must be occasions when it passes between the Sun and the Earth. If the orbits of the two planets were in exactly the same plane, we would see Mercury cross across the Sun's disk every time that lineup happens. However, the orbits are not in the same plane; the plane of Mercury's orbit is inclined about 7° to that of Earth. The two planes intersect at only two points; these correspond to the time that Earth, in its annual orbit around the Sun, is experiencing the beginning of May and the beginning of November.

Mercury transit from Boston