For the love of Venus

The big Zeiss telescope that dominates the Stardome observatory has been the domain of Dr Grant Christie for many years. Here, the skies are monitored and alien planets are discovered in other galaxies. Next week this 21st-century equipment will look at the cosmic event that led to the birth of New Zealand.

Dr Christie will use the telescope to track the transit of Venus across the sun, recording footage and stills that will be shared with the world.

"Astronomers and astronomy enthusiasts around the country are gearing up their telescopes and getting ready not just to look at it themselves but also to share it with the people in their communities," he says. Transits of Venus are extremely rare celestial events.

They occur in a pattern that repeats every 243 years, with pairs of transits eight years apart separated by long gaps of 121.5 and 105.5 years.

On June 6, we will be able to watch a black dot travelling across the bright disc of the sun from 10.15am to 4.43pm. We're advised to wear a special solar viewing device because looking directly at the sun can damage our eyes.

"It's an opportunity to see a very rare event that was an important part in the establishment of New Zealand in its modern form," says Dr Christie, president of the Auckland Astronomical Society and vice-president of the Royal Astronomical Society of NZ. "The transit of Venus is intimately tied to our history."

It was why Captain James Cook went to Tahiti in 1769. He was sent to observe the event to calculate more accurately the distance of Venus from the sun, which would enable astronomers to calculate other planets' distances from the sun.

"He was trying to establish the true distance from Earth to the sun, which is a very important number for astronomers.

"It is like a ruler that we use to ultimately measure the size of the universe," explains Dr Christie.

Eventually, Cook came to New Zealand, mapped the country and observed the transit of Mercury from the place now known as Mercury Bay, surrounding Whitianga on the Coromandel Peninsula's east coast.

Today, Dr Christie says astronomers are interested in the transit of Venus because it gives them a close-up look at what's going on when a planet passes in front of a star.

This is one of the methods they use to discover exoplanets - planets outside our solar system.

"Astronomers are daily, or nightly, looking at transits of alien planets around distant stars. We're using this (transit of Venus) as a test method to understand that process better," he says.

When planets go around their star, some of them will eventually pass in front of their star and the light from their star will dim.

"Thousands of planets have been discovered that way," he says.

Astronomers are also curious to know whether they can detect Venus' atmosphere from watching the sun's light passing through it.

An atmosphere is a layer of gases that surrounds a body of mass, and is held in place by that body of mass.

"Some astronomers are interested to see how much of the chemistry of the atmosphere of Venus we can decipher from the observation of the sun's light shining through the atmosphere because that situation occurs around distant stars, when planets, some of which will have an atmosphere, pass in front of their stars.

"Astronomers are interested to see whether it's possible to really detect a distant planet's atmosphere many light years away around another star altogether."

Dr Christie believes that by 2117, for the next transit of Venus, astronomers will have powerful telescopes that will help them establish the chemistry of a planet's atmosphere and possibly detect the presence of life.

"They will be able to study planets that today we only know exist.

"They will have capability to analyse the atmosphere within the planet and see whether they have oxygen, whether any of the planets would have life."

In 100 years, he says, space-based telescopes will be able to study these events in exquisite detail.

For now, says Dr Christie, New Zealand astronomers are part of a co-ordinated global network monitoring events in the universe as Earth turns.

"It's very seldom that it is just one telescope looking at something to make a discovery.

"It's usually a lot of them working in unison. The sun never rises but in a good way."

EVENTS FOR THE TRANSIT

Wine and the stars

Stardome's Night Sky show includes cheese and wine on June 5. Learn about planets, stars and constellations visible in the night sky. Tickets include courtyard telescope viewing after the show (weather permitting).

WHAT Wine, Cheese and Astronomy

WHERE Stardome, 670 Manukau Rd, One Tree Hill Domain

WHEN June 5, 8-9.30pm

HOW MUCH $25, R18. ph 624 1246 or email info@stardome.org.nz

WEB stardome.org.nz

Stardome Public Open Day: On June 6 from 10am-5pm there will be a public open day at Stardome. Stardome has bought a new solar telescope to watch the transit and there will be free courtyard telescope viewing. There will also be short planetarium shows explaining the transit (gold coin donation), which won't occur again for 105 years. A live feed will run to a big screen at Stardome and is also at stardome.org.nz

Auckland Museum on transit day: Auckland Museum has viewers and telescopes and on June 6 from 11am-3pm will have astronomical experts available along with storyteller Pita Turei to give a Maori perspective. Free, outside the northern entrance steps.

Lecture: Stardome astronomer Grant Christie will give a public lecture about the transit in the Auckland Museum auditorium on Saturday, June 2, at 2pm (30-45 mins). Children 7 years and over welcome. For more information see aucklandmuseum.com (events calendar).

SOLAR PATTERNS

Transits of Venus occur eight years apart, separated by long gaps of 121.5 years and 105.5 years.

'Recent' history and future pattern:

December 1874; December 1882; June 8, 2004; June 5-6, 2012; December 2117; December 2125