Mercury puts on rare show as it passes across the sun

Mercury is passing in front of the sun Monday in a rare phenomenon

Mercury is passing in front of the sun Monday in a rare phenomenon

Mercury has to be in the right place and the right time to move around the sun kilometres making the transitions very rare.

During the transit, Mercury appears as a dark silhouetted disc against the bright surface of our star.

More details on the viewing event are available here.

In this composite image provided by NASA, the planet Mercury passes directly between the sun and Earth on May 9, 2016 in a transit which lasted seven-and-a-half-hours. Earthlings get treated to only 13 or 14 Mercury travels a century.

If you can't get hold of a telescope with solar filters to see for yourself, then you can watch a live broadcast of the transit, such as the one below.

Mercury typically transits the Sun in either May or November.

Mercury is the solar system's smallest, innermost planet.

"Another use of transits is the dimming of Sun or starlight as a planet crosses in front of it". "So far, TESS has discovered 29 confirmed exoplanets using transits-with over 1,000 more candidates being studied by scientists".

When this happens, Mercury will be visible from the Earth as a tiny dot about 0,5 per cent of the diameter of the sun itself.

Planetary transits also provide astronomers with enough information to determine a planet's size and how far away they are from their host stars. "So Mercury's going to most likely be excessively little". "Though it takes Mercury only about 88 days to zip around the sun, its orbit is tilted, so it's relatively rare for the sun, Mercury and Earth to line up perfectly".

"It can lead to serious and permanent vision damage".

To spot the small disc of Mercury against the Sun you will need a telescope with a magnification of at least 50x. "Always use a safe Sun filter to protect your eyes".