November 11, 2019 - 11:20 AMT
Mercury to pass between the Earth and the Sun on November 11

A rare transit of Mercury will take place on Monday, November 11, when the smallest planet in the Solar System will pass directly between the Earth and the Sun. The last time this happened was recent, in 2016, but the next won’t be until 2032. During the transit, which takes place in the morning in the United States and in the afternoon in the UK and Europe, Mercury will appear as a dark silhouetted disc set against the bright surface of the Sun, SciTechDaily reports.

The transit begins at 1235 GMT, when the edge of Mercury appears to touch the edge of the Sun, and ends at 1804 GMT when the edge of the silhouetted planet appears to leave the Sun. Observers in different locations will see the transit taking place up to 2 minutes before or after these times, as the planet will appear to take a slightly different path across the Sun.

On the morning of November 11, UK amateur astronomical societies and public observatories will be running events where members of the public can safely enjoy the transit, as well as live webcasts of the spectacle. The Royal Astronomical Society will be supporting a (free) event run by the Baker Street Irregular Astronomers in Regent’s Park, central London, where members of the public can book places to come and view the transit using appropriate equipment at no cost.

The entire event is visible from the eastern United States and Canada, the south-western tip of Greenland, most of the Caribbean, central America, the whole of South America and some of west Africa. In Europe (including the UK), the middle East, and most of Africa, the sun will set before the transit ends, and so the latter part of the event will not be visible. In most of the United States and Canada, and New Zealand, the transit will be in progress as the sun rises. Observers in eastern Asia, southern and south-eastern Asia, and Australia will not be able to see the transit.

There are 13 or 14 transits of Mercury each century, so they are comparatively rare events, though each one can typically be seen over a large area of the Earth’s surface. A transit was first seen in 1631, two decades after the invention of the telescope, by French astronomer Pierre Gassendi.