Venus to Cross the Sun

MEDIA RELEASE - 12th March, 2012

Venus to Cross the Sun

New Zealanders will have the extremely rare chance to watch the planet Venus in transit across the face of the Sun on Wednesday the 6th of June. This opportunity will not occur again for 105 years.

From 10:15am until 4:43pm, viewers will be able to observe a black dot travelling across the bright disk of the Sun. A solar viewing device is essential to avoid damaging the eyes.

Transits of Venus across the Sun were once considered to be of the greatest importance to science, and huge efforts were expended trying to record them. In the 18th century the size of the universe was one of the great scientific mysteries. Astronomers could measure how far away celestial objects were by ‘Astronomical Units’ (the distance of the Earth from the Sun). However they had not yet defined this distance accurately in kilometres or miles.

The explorer James Cook was despatched to Tahiti in 1769 to record the times of this phenomenon. The primary purpose of the observation of the transit of Venus was to obtain measurements that could be used to calculate more accurately the distance of Venus from the Sun. If this could be achieved, then the distances of the other planets could be worked out, based on their orbits. After observing the transit, Cook continued on to New Zealand where he and his crew aboard the HMS Endeavour were the second recorded Europeans to visit. During their visit Cook observed the transit of Mercury, and created the first nearly complete map of the New Zealand coastline.

On the 6th of June this year it will take Venus over 6 hours to cross the face of the Sun, so there will be plenty of time to see the event, weather permitting of course. Apart from using your own telescope with a solar filter, your best chance to get a really good look is to attend one of many public transit viewing events hosted by local astronomical societies and observatories around the country. Most of these will have specialised instruments available that provide spectacularly good views of the Sun in perfect safety.

For those in the Auckland region, Stardome Observatory & Planetarium will be hosting a public open day for watching the transit of Venus on the 6th of June. Stardome will be open from 10am to 5pm with free viewing through their courtyard telescopes, which have all been fitted with new solar filters. Short planetarium shows explaining the transit will also run throughout the day for a gold coin donation.

Stardome has purchased a new solar telescope in anticipation of this event. The Lunt solar telescope is mounted on the side of the Edith Winstone Blackwell memorial Zeiss telescope as an auxiliary instrument.

A live feed from the new solar telescope will be running to a big screen to enable as many people as possible to view at once. This live feed will also be on the Stardome website for those unable to visit. Feeds from other international observatories will be obtained as a backup in case of poor weather.

From Earth, the only planets we can ever see in transit across the face of the Sun are Mercury and Venus – the so-called ‘inferior’ planets because they orbit between the Earth and the Sun. Transits of Venus occur in pairs separated by eight years. Each pair is in turn separated by an alternating interval of 105.5 and 121.5 years, making a cycle of 243 years. The last transit of Venus was in June 2004, where modern instruments gave the best views ever, but New Zealand was not in a prime viewing position like we will be for this opportunity. The next transit of Venus will not be seen from Earth until 2117, but again New Zealand will be well placed to view the entire event.

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