At precisely 8.16am on Wednesday, June 6 Queenslanders can watch a tiny, but significant dot like a round, legless bug begin to crawl across the face of the sun.
The dot is super hot Venus, the planet that rains metal ‘snow’, passing between Earth and the sun, says Queensland University of Technology’s Dr Stephen Hughes, a senior physics lecturer in QUT’s Science and Engineering Faculty.
He said the transit will take about six hours, plenty of time to have a look before the next chance comes around on December 11, 2117.
“Venus has become brighter in the lead-up to June 6 because the distance between Venus and Earth is getting smaller and smaller and will reach a minimum half way through the transit, Dr Hughes said.
“At this moment Venus will transition from being an evening star to a morning star.
“Despite its beauty Venus is a very inhospitable planet because it is enshrouded in thick clouds of sulphur acid suspended in an atmosphere of carbon dioxide with an average temperature of 460 degrees Celsius.”
Dr Hughes said Venus and Mercury were the two inner planets that orbit the sun “in front of us”. The other planets were further away and orbit the sun “behind” us.
He said the transit of Venus was historically significant to Australians and New Zealanders.
“The transit of Venus is what sparked Captain Cook’s voyage on the Endeavour in 1769, the three-year voyage during which he came upon New Zealand and then Australia.
“The English astronomer Edmond Halley (Halley’s comet) was the first to point out that observations of the transit of Venus from different parts of the Earth could be used to measure the distance to Venus which would then allow the overall scale of the solar system to be calculated.
“Astronomy was advanced enough to predict the next transit would occur on 3 June 1769 on the other side of earth from England in the Pacific and so the British Admiralty sent Cook to Tahiti to record the transit from there.
“The solar system is like a giant, but very accurate clock with eight hands – each hand being a line drawn between the sun and one of the planets.”
Dr Hughes said that although the Endeavour had the most sophisticated equipment of the time – a magnetic compass, an octant – a device which could accurately measure the angle of a celestial body above the horizon and lunar charts, this voyage was akin in danger to the Apollo 11 flight to the moon 200 years later in 1969.
“The idea behind the Tahiti expedition was to record the precise time of the first and last contact of Venus with the sun,” Dr Hughes said.
“These time measurements could then be combined with the timing of transit observations from other parts of the world to use the triangulation principle used by surveyors to measure distance.”
Cook and his crew observed the transit of Venus from start to finish in Tahiti. Cook then opened sealed instructions which ordered him to sail south and look for ‘terra Australis incognita’ the great southern continent believed to exist to counterbalance the northern hemisphere’s land mass.
“Cook headed west and eventually came to New Zealand and then explored the east coast of Australia before passing through Indonesia on the way back.”
Media contact: Niki Widdowson, QUT media officer, 07 3138 2999 or firstname.lastname@example.org