A rare transit of Mercury will take place on 11 November, when the smallest planet in our Solar System will pass directly between the Earth and the Sun. The last time this happened was in 2016, and the next will be in 2032. During the transit, which takes place in the afternoon in the UK, Mercury will appear as a dark silhouetted disc set against the bright surface of the Sun.
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 11 November, 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.
Professor Mike Cruise, President of the Royal Astronomical Society, is keen for people to experience the transit for themselves. "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, and everyone with access to the right equipment should take a look, or go to an organized event if the weather is clear, or alternatively follow one of the live webcasts. I do want to stress though that people must follow the safety advice – looking at the Sun without appropriate protection can seriously damage your eyes."
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.
On Monday (Nov. 11), Mercury will move across the sun's face and several spacecraft will have their sights set on the rare event.
Spacecraft have captured incredible images of past Mercury transits, and this year promises some exciting observations from space. NASA's Solar Dynamics Observatory (SDO) and Solar & Heliospheric Observatory (SOHO) will be watching the sun during Mercury's roughly 5.5-hour trip, and a Japanese mission may also provide a close-up glimpse.
On Earth, skygazers in North America, South America, Europe, Africa and even Antarctica can view the event using safe ISO-certified protective solar-viewing gear — weather permitting. Those in Alaska, the Pacific and Asia won't catch the event, because the sun will be below the horizon when Mercury passes in front of the star like a traveling blemish. Fortunately, the teams behind several space missions will be sharing unobstructed views of Mercury's transit.
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A team from SDO will regularly update its website with the latest views of Mercury's Nov. 11 transit, accessible here starting at about 7 a.m. EST (1200 GMT), about half an hour before Mercury's first contact (when the planet's silhouette is tangent to the solar disk for the first time).
NASA also runs SOHO, a 12-instrument spacecraft built in collaboration with the European Space Agency. SOHO has been in space longer than SDO, having launched over two decades ago. It keeps regular tabs on the sun and produces several time-lapse views of the sun in gif-movie format. Like SDO, they are regularly updated on NASA's website. Mercury will likely appear in these views, albeit perhaps as a speeding spot in an accelerated time-lapse video. SOHO videos can be viewed here.
Jodi