The planet Mercury is the closest to the Sun, reaches 700 degrees centigrade, is only slightly larger than the Earth’s Moon, and, of the planets known to the ancients, is the most difficult to locate in the sky. Mercury has roughly three “days” for every two of its “years.” The next transit of Mercury [across the sun] will happen … 11 Nov 2019 starting 12:35 and ending 18:04. – from Planet Mercury by David A. Rothery