A rare glimpse of Pluto is expected to wow astronomers tomorrow morning, and those in Dunedin and Central Otago will have some of the best seats in the house - for about 90 seconds.
The eclipse-like phenomenon, known as a stellar occultation, will see Pluto pass in front of a star and is scheduled to begin about 5am on Tuesday.
The far-flung event will only just be visible on super-powered observatory telescopes, so backyard astronomers shouldn't get their hopes up, but scientists will be in place throughout New Zealand to record the back-lit planet. They will have less than two minutes to catch it.
Dunedin Astronomical Society president Ash Pennell says he shares the excitement of the many international astronomers who have flocked to New Zealand to view the event.
He would be making observations using the main telescope at the society's Beverly Begg Observatory well before 5am tomorrow and all information about the potential sighting, including a video recording, would be shared collaboratively with the Royal Astronomical Society of New Zealand.
The event was definitely "something interesting'', and although a powerful telescope was needed to see anything, Otago was, weather permitting, one of the best places on Earth to observe it, he said.
He had never seen such an event involving Pluto before, and noted that observing such eclipse-like events previously had added significantly to mankind's knowledge of Pluto.
In Central Otago, NIWA atmospheric scientist Richard Querel will also be watching the skies through powerful telescopes at NIWA's atmospheric research station at Lauder - a part of New Zealand renowned for its clear skies.
While 90 seconds might be a slim window, Dr Querel said significant discoveries were able to be made during the last event.
"And it just so happens that the way things are positioned, one of the best places to observe this very short event is going to be over the south of New Zealand," he said.
In Auckland , Stardome Observatory astronomer Grant Christie said a team from Massachusetts Institute of Technology would be at the Cornwall Park venue to record the phenomenon.
It will inform the data recorded from NASA spaceship New Horizons which is due to reach Pluto in about two weeks, Mr Christie said.
"When the spacecraft was launched it wasn't known that Pluto would pass in front of the star, it can't be worked out that far in advance, it's just a happy coincidence. And the extra part of it is that the only land on earth with telescopes installed that can see it is New Zealand and Tasmania," he said.
A stellar occultation led to the discovery of Pluto's atmosphere in 1988 - and the rare events yield important scientific data whenever it occurs.
The last time this happened was 2006 when significant discoveries about Pluto, including its many moons, were made from just a few seconds of exposure.
"The sky is full of stars but Pluto is very tiny so it actually doesn't happen very often," Mr Christie said.
"But right now we've got our fingers crossed that there'll be clear sky between 4 and 6 tomorrow morning which, given the forecast, is pretty uncertain but we'll be very disappointed if we get clouded out."
Researchers were particularly keen to see how measurements made from Earth will compare with those from New Horizons as it flies by in a matter of weeks, collecting data and images never seen at such a short distance.
Astro-biologist Haritina Mogosanu said the occultation would be fleeting because it was such a "dynamic" process.
This event was even more special because NASA plane Sofia - a stratospheric observatory which houses a telescope and operates on an annual budget of $80 million - was in New Zealand to record it, she said.
"Occultations can last a few minutes or even less than that. Everything is moving, it's a dynamic process. Pluto is moving, the star is moving, the earth is moving, so it takes a very short time for an occultation to occur.
"But if we take many, many pictures of what happens we can see it. Sofia is going to be in the best conditions to do that."
Ms Mogosanu has been invited on board Sofia for a night-flight at the end of the week - a dream come true, she said.
The idea is to eventually make Sofia accessible for New Zealand school teachers, she said.
"It's extraordinary... I love airplanes, my dad was a pilot, and to me the most beautiful thing in this whole universe is a telescope inside of an aircraft," she said.
- John Gibb and the New Zealand Herald