WASHINGTON • The planet Mercury will pass between the Earth and the Sun today, a rare celestial event that has excited astronomers and sky watchers alike.
It will look like a black dot gliding across the Sun's face, according to the National Aeronautics and Space Administration (Nasa).
This year's Mercury transit, as the event is known, will be widely visible - weather permitting - from most parts of Earth, including the Americas, New Zealand, Europe, Africa and western Asia.
It starts today at about 7.35am Eastern Standard Time (8.35pm Singapore time) and will last nearly six hours.
A Mercury transit happens only about 13 times a century. The last one was in 2016 and the next will not happen until 2032.
Nasa is warning people against looking directly at the Sun because that can lead to permanent eye damage. The US agency says a telescope with a minimum magnification of 50 times or binoculars with a solar filter can be used.
Sky watchers should look for Mercury's tiny disk, jet black and perfectly round, covering just a fraction of the Sun's blinding surface.
Scientists have used these events for hundreds of years to study the way planets and stars move in space.
Nasa is urging teachers and parents not to miss the opportunity to teach children about the solar system.
"Viewing transits and eclipses provides opportunities to engage the public, to encourage one and all to experience the wonders of the universe and to appreciate how precisely science and mathematics can predict celestial events," Dr Mitzi Adams, a solar scientist at Nasa, said in a blog post on Friday.