Transit of Mercury

Transit of Mercury on November 8, 2006 with sunspots 921, 922, and 923

A transit of Mercury across the Sun takes place when the planet Mercury comes between the Sun and the Earth, and Mercury is seen as a small black dot moving across the face of the Sun. On November 8, 2006, the planet Mercury could be last seen going across the sun. The best place to have observed the transit on that date was in Hawaii.Transits of Mercury with respect to Earth are much more frequent than transits of Venus, with about 13 or 14 per century, in part because Mercury is closer to the Sun and orbits it more rapidly.Transits of Mercury can happen in May or November. November transits occur at intervals of 7, 13, or 33 years ; May transits only occur at intervals of 13 or 33 years. The last three transits occurred in 1999, 2003 and 2006 ; the next will occur in 2016.During a May transit, Mercury is near aphelion and has an angular diameter of 12" ; during a November transit, it is near perihelion and has an angular diameter of 10".

Close-up of Mercury during the Nov. 8, 2006 Transit

Grazing transits of Mercury:

Sometimes Mercury only grazes the Sun during a transit. In this case it is possible that in some areas of the Earth a full transit can be seen while in other regions there is only a partial transit (no second or third contact). The transit of November 15, 1999 was such a transit, and the previous one before that was on October 28, 743. The next such transit will occur on May 11, 2391.It is also possible that a transit of Mercury can be seen in some parts of the world as a partial transit, while in others Mercury misses the Sun. Such a transit last occurred on May 11, 1937, and the previous one was on October 21, 1342. The next such transit will occur on May 13, 2608.

Simultaneous transits:

The simultaneous occurrence of a transit of Mercury and a transit of Venus is extremely rare, and will next occur only in the years 69,163 and 224,508. The last simultaneous transit occured in 373,173 BC. On September 13, 13,425 an almost identical event is predicted: a transit of Mercury and a transit of Venus will follow one after the other, in an interval of only 16 hours.The simultaneous occurrence of a solar eclipse and a transit of Mercury is very rare. The last time this happened was August 27, 11436 BC. The next solar eclipse occurring during a transit of Mercury will be on July 5, 6757, and will be visible in Eastern Siberia.