A rare transit of Mercury will take place on Monday, November 11, when it passes between the Earth and the Sun and the next transit time will be only in 2032. The transit of the smallest planet in our Solar System will take place during the evening in most parts of Asia and Europe, so Mercury will appear as a dark silhouetted disc set against the bright surface of the Sun.

The transit begins at 1235 GMT and ends at 1804 GMT, when Mercury appears to enter on one edge of the Sun and exit on the other. Observers will get to 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, said the Royal Astronomical Society.

On the morning of 11 November, UK amateur astronomical societies and public observatories will webcast the spectacle while the Royal Astronomical Society will join a free event run by the Baker Street Irregular Astronomers in Regent's Park, central London.

Prof. Mike Cruise, president of the Royal Astronomical Society said, "This is a rare event, and we'll have to wait 13 years until it happens again.Transits are a visible demonstration of how the planets move around the Sun." However, he warned that looking at the Sun without appropriate protection can seriously damage the eyes.

The event is visible from the eastern United States and Canada, the south-western tip of Greenland, most of the Caribbean, central America, Southern America and some of west Africa. In Europe, the Middle East, and most of Africa, the sun will set before the transit ends, so the latter part will not be visible.

In most of the US 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. Mercury's orbit around the Sun takes 88 days to complete and it passes between the Earth and Sun every 116 days.

A visible transit happens only when the Earth, Mercury and the Sun are exactly in line in three dimensions. On an average, there will be 13 or 14 transits of Mercury each century. the first transit was seen in 1631, almost 20 years after the invention of the telescope by French astronomer Pierre Gassendi.

Transit of Mercury
Transit of Mercury across the Sun Wikipedia / Elijah Mathews

Since Mercury blocks out a tiny part of the light from the Sun, it should not be seen using the pinhole projectors that worked successfully in the solar eclipse in March 2015, or by using 'eclipse glasses' with solar filters. All telescopes with safe filters will be appropriate. During the transit, when Mercury is close to the edge of the Sun, it is possible to see the 'black drop' effect, where a broad line appears to connect the planet to the solar limb.

So far, two NASA space probes have visited Mercury, Mariner 10 in 1974 and 1975, and MESSENGER, which orbited the planet from 2011 until a deliberate crash landing in 2015. The next European Space Agency mission BepiColombo launched in 2017, will study the planet from 2024 onwards.