Transits of Mercury are rare, with only 13 or 14 occurring each century. Luckily, one is coming up on 9 May 2016. This event, known as a transit, will be visible from most of western Europe, including the UK and Ireland, as well as South America and the eastern parts of North America.
After Monday’s transit the next one will not be until 11 November 2019.
ESA will be live streaming the event, but the transit can be observed using a dedicated solar telescope or properly filtered astronomical telescope.
Mercury will appear 1/150th the size of the Sun’s diameter as it crosses the disc and will be too small to spot with the naked eye. For this reason, eclipse glasses and other kinds of eye protection for looking at the Sun will be unsuitable. Viewing the Sun with the naked eye or an unfiltered regular telescope is incredibly dangerous and could cause permanent blindness.