Because Mercury is so close to the Sun, it is hard to directly observe from Earth, except during twilight. Mercury makes an appearance indirectly, however 13 times each century, Earth observers can watch Mercury pass across the face of the Sun, an event called a transit. These rare transits fall within several days of May 8 and November 10. The first two transits of Mercury in the 21st century occured in May 2003 and November 2006. The next transit will occur on May 9, 2016.