The chairperson of Astronomy Ireland has warned the public not to attempt to view today’s transit of Mercury across the sun with telescopes or binoculars.
David Moore advised that Mercury is so small that would not be visible to the naked eye and that special optical aids would be required to view the event.
Astronomy Ireland has set up special telescopes at its headquarters in Blanchardstown, Dublin and will also be streaming the transit from observatories around the world.
A transit of Mercury across the Sun takes place when the planet Mercury comes between the Sun and the Earth, and Mercury is seen as a small black dot moving across the face of the Sun, according to Astronomy Ireland.
Mr Moore told Newstalk Breakfast that the passing of Mercury in front of the sun is “a rare transit”. It will occur for six hours today.
“The last time it did it was only three years ago, but the next time will be 13 years from now. If you're living in North America, you won’t get to see it again for 30 years. So, they're quite rare events.”
He explained that while Mercury is the fastest planet orbiting the sun, every three months or so, the sun is a hundred times wider than the earth “and all the geometry means it's going to take about 12.30 today until 6pm for Mercury to cross the sun, as seen from the earth.
“We're moving as well, so it's a complicated orbital dance that the three of us, the sun, the earth and Mercury are playing and it translate into this six hour window.
“We'll miss the end because the sun will set soon after 4pm," he said, "(but) we'll get to see the start and the middle - the best bits.”
Mr Moore cautioned people that looking at the sun is dangerous to the naked eye.
“You have to be careful...Don't point telescopes or binoculars at the sun; don't even stare at the sun," he warned.
"Mercury is too small - it's 200 times smaller than the sun. It's a tiny dot that wouldn't be visible to the naked eye. You do need optical aid - that's why we're setting up telescopes at our headquarters in Blanchardstown.”