Through an amateur telescope, Mercury would appear as a small dot against the sun on the morning of November 12. Photo / File
Through an amateur telescope, Mercury would appear as a small dot against the sun on the morning of November 12. Photo / File
New Zealand history is set to repeat itself in a very cosmic way, when a rare astronomical event plays out this month.
On Tuesday morning, November 12, Mercury will move between the Earth and the Sun on its orbit – making its silhouette visible against the Sun's disc as it travels.
It just so happens that the spectacle will unfold exactly two and a half centuries - give or take a day - after it was observed in Coromandel by Charles Green, an astronomer who arrived in New Zealand with Captain James Cook's first voyage.
The location they chose was named Mercury Bay – and the exact spot at Cooks Beach was marked with a stone cairn. Stardome astronomer Dr Grant Christie said November 9, 1769, happened to be clear weather, enabling Green a good view of the solar system's innermost planet.
"They noted that Mercury seemed like a little disc against the sun and implied that it didn't have a big fuzzy atmosphere."
But while significant, it didn't prove as important as the transit of Venus, which the crew observed from Tahiti several months earlier.
It was that event that effectively enabled scientists to calculate the mean distance from the Sun to the Earth.
Cooks Beach in Coromandel was chosen by Captain James Cook's crew as the spot to observe the transit of Mercury in November 1769. Photo / File
The transit of Mercury occurs much more often – about 13 times each century – yet it is set to happen 250 years after Green spied it, and will again, 500 years to the day, on November 10, 2269.
Although Mercury would take about five and a half hours to pass across the Sun, Kiwis will have just a brief opportunity to view it at sunrise, between 6am and 7am.
"It will be highest across the sky at the end of the event, at about 17 degrees, which is very low," Christie said.
"So at that altitude, you'll be looking through a lot of atmosphere – maybe 10 times the amount that you would if looking straight overhead.
"You're not going to get a very sharp image of it – but you'll certainly see a black dot if you've got a telescope designed to look at the sun.
But he warned against trying to view it with the naked eye, as looking directly at the Sun can damage your eyes.
"It's important that people don't try to pull out their binoculars and watch it, as that would be a disaster."
Christie expected the transit would be best viewed from across the sea – and funnily enough, Mercury Bay is still a prime position.
A replica of Captain James Cook's Endeavour has been visiting the country to mark his voyage here 250 years ago. Photo / File
Meanwhile, Otago Museum is marking the event with its nationwide Mercury Rising project Te Mahutatanga o Takero, celebrating the astronomical mātauranga of Māori, alongside the modern understanding of astrophysics.
The project – featuring free public talks in Auckland, Whitianga, Wellington, Christchurch and Dunedin - was created and driven by Dr Ian Griffin, celestial photographer, aurora chaser, and Otago Museum director.
"It is such a great opportunity to showcase the rich bicultural tradition of astronomy in New Zealand, as well as present the cutting-edge science that is happening right now from our shore," Griffin said.
"We have some of the leading astronomers in New Zealand and the world sharing their knowledge, and it will be amazing to get Aotearoa excited about the night sky."
