The next one won’t be happening until 2117, so stargazers are preparing for the transit of Venus across the face of the sun tonight, and NASA will be hosting a live webcast from Mauna Kea in Hawaii to give a real-time view of the entire transit as it unfolds between 5 and 6 June, depending on where in the world you are.
While stargazers in Ireland will have to wait until sunrise tomorrow morning on 6 June to catch a glimpse of the transit of Venus, those on the east coast of North America will be able to witness the event at sunset this evening.
As for the NASA live webcast from Hawaii, it will begin at 9.45pm UTC (11.45am local Hawaiian time or 5.45pm EST) this evening. That means 10.45pm BST.
The transit itself will take more than six and a half hours. Astronaut Don Pettit will also be photographing the transit from the International Space Station.
According to David Moore of Astronomy Ireland, such transits of Venus across the face of the sun occur roughly more than every 100 years in pairs separated by eight years. The last such transit of Venus was in 2004.
For centuries, scientists have been using Venus transits to understand the size of the solar system and the distances between the Earth and the sun.
Viewing the transit safely – don’t stare at the sun with the naked eye
So now is our chance to view the Venus transit, as there won’t be another one experienced anywhere on Earth for the next 105 years.
People will have to be careful when watching the transit, however. NASA said sunglasses won’t be enough protection for solar viewing, and even if people are using solar filters or solar viewing glasses they should take regular breaks from viewing the transit to give their eyes a rest.
People who will catch a glimpse of the Venus transit across the sun will see Venus, which is 30 times smaller than the diameter of the sun, as it crosses the ball of fire.
In Ireland, we will be able to experience the last hour of the transit, as Venus comes off the disc of the sun.
For stargazers in Ireland, people will be able to see the end of the transit around 4.50am until 5.50am, depending on where they are when the sun rises.
In Dublin, Astronomy Ireland will be at Skerries Harbour tomorrow at sunrise to allow people see the transit using special telescopes with solar filters.
However, for people who can’t make it, the site has information on how people can view the Venus transit safely, using a handmade ‘pinhole camera’.