Rare transit of Mercury
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A rare astronomical event will take place on Monday, November 11, when the smallest planet in our Solar System, Mercury 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 appears as a tiny dark silhouetted disc set against the bright surface of the Sun.
The transit begins at 12.35 GMT, when the edge of Mercury appears to touch the edge of the Sun, and ends at 18.04 GMT when the edge of the silhouetted planet appears to leave the Sun.
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.
Mercury completes each orbit around the Sun every 88 days, and passes between the Earth and Sun every 116 days.
As the orbit of Mercury around the Sun is tilted compared with the orbit of the Earth around the Sun, the planet normally appears to pass above or below our nearest star. A transit can only take place when the Earth, Mercury and the Sun are exactly in line in three dimensions.
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.
At any time, Mercury blocks out no more than a tiny part of the light from the Sun.
This means that the event should not be viewed with the naked eye.
Looking at the Sun without appropriate protection, either during the transit, or at any other time, can cause serious and permanent damage to the eyes.
The Society for Popular Astronomy has an online guide on how to safely view the transit, for example by projecting the solar image with binoculars or a telescope which can be found at https://www.popastro.com/main_spa1/transit-of-mercury-2019/
Online live stream are also available via https://www.facebook.com/royalmuseumsgreenwich/posts/2655277881189689 and https://www.youtube.com/watch?v=GNvZHR91e4s
A public viewing event is also being held by the Cairngorms Astronomy Group in Tomintoul with details from https://www.facebook.com/events/3248497375165439/
