The passage of the planet Mercury directly between the Earth and the sun, visible as a tiny black dot creeping across the solar disk over several hours, observable only with proper solar-viewing equipment because Mercury's apparent size is far too small to see with the naked eye. Transits of Mercury occur roughly thirteen times per century, far more often than transits of Venus, because Mercury's faster, closer orbit brings it into alignment more frequently.
Facts
PeriodicityAbout 13 or 14 times per century 1 ScaleApparent size of about 12 arcseconds, too small to see without a telescope 1 First DescribedFirst observed by Pierre Gassendi on 7 November 1631 1 Identification
Distinguishing AppearanceA tiny black dot moving across the Sun 1 Sources
1. Transit of Mercury, Wikipedia
Introduction paragraph
they occur about 13 or 14 times per century, much more frequently than transits of Venus
History
The first observation of a Mercury transit was observed on November 7, 1631 by Pierre Gassendi.
Observation, appearance paragraph
Mercury appears as a tiny black dot moving across the Sun as the planet obscures a small portion of the solar disk
Observation, visibility paragraph
At inferior conjunction, the planet Mercury subtends an angle of 12″, which, during a transit, is too small to be seen without a telescope.
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