Skygazers await Transit of Mercury

On May 9, the smallest and innermost planet in our solar system will pass between Earth and the sun, visible through a telescope as a tiny black dot moving across the face of the sun

Start: 11:12GMT

Length of transit: 7hrs, 30min

Greatest: 14:57GMT

End: 18:42GMT

TRANSIT

Orbital planes align in May and November each year but as planets travel at different speeds, transit occurs only a dozen times a century

In May, Mercury reaches aphelion – furthest point from sun – but proximity to Earth makes planet look larger

PLANET MERCURY

Closest planet to Sun Diameter: 4,800km Mercurian year: 88 days Equator surface temp: 450C

Plane of Mercury’s orbit

7˚

Plane of Earth’s orbit

Full transit visible

Transit at sunset

No transit visible

Never look directly at sun with naked eye, binoculars, cameras or telescopes without specialised solar filters

Source: NASA, www.eclipsewise.com