A rare transit of Mercury will send a dark spot gliding across the face of the sun on Wednesday, November 8. For nearly five hours, the closest planet to the sun will appear as a tiny silhouette against the solar disk.
Webcams are being set up to broadcast the event live on the internet. One of the best will come from mountaintops on Hawaii and can be viewed here. As well as live images, the site will compile and show time-lapse movies of the spectacle.
If you live within the region of visibility, remember the safety rules for viewing the sun. Mercury will only be visible with a telescope but you must use an approved solar filter. A safer method is to project the sun’s disk through your telescope onto a piece of white card.
The next transit of Mercury visible from the British Isles will not occur until May 9th, 2016. Only the early stages will be visible before the sun sets. The last visible from the UK was on May 7, 2003.
Transits of Mercury only happen in May or November at intervals of seven, 13, or 33 years. A Nasa page about the phenomenon is here. The photo is of a projected image of the 2003 transit, by Paul Sutherland. Mercury is the tiny dot to the left – the other blot is a sunspot.