Mercury is the innermost planet in the solar system. It is also the smallest, and it is considerably smaller now than it was from the beginning. The surface layer on the planet consists of a solid crust of stone, and the temperature varies between –173 and +427 degrees Celsius.
Since Mercury is so close to the sun it can be difficult to see, but sometimes it is visible to the naked eye or with binoculars at dawn or dusk. About 13 times a century, Mercury passes between the earth and the sun. The planet then appears as a small circular spot on the solar disk.
On Monday, November 11, it will be possible to see when Mercury crosses the solar disk, via a solar telescope at the Umeå science center - if the weather permits. Is that clear then beware - the next chance comes in 2032.