A RARE astronomical event that led to Captain Cook's discovery of Australia -The Transit of Venus - promises a spectacular feast for stargazers this week.
The phenomenon, which occurs when Venus passes across the face of the Sun, will take place on June 6 for only the second time in a century.
Head of the astrophysics group at the UQ School of Mathematics and Physics, Professor Michael Drinkwater said people could not look at the sun without damaging their eyes, but could safely witness the event by viewing a live broadcast on UQ's website, fed from specially outfitted telescopes at The University of Queensland's St Lucia campus.
"Transits of Venus occur in pairs that are eight years apart, and separated by gaps of a little over a 100 years," Professor Drinkwater said.
"The event occurred last on June 8, 2004, and will not reoccur until December 11, 2117.
"Transits of Venus are more rare than Halley's Comet, which appears every 75 to 76 years."
Only six transits of Venus are known to have been observed by humans before: in 1639, 1761, 1769, 1874, 1882 and 2004.
Professor Clive Moore, Head of UQ's School of History, Philosophy, Religion and Classics, said Captain James Cook travelled to the island of Tahiti in 1769 to observe the Transit of Venus.
It was on that expedition that he later discovered the east coast of Australia.
"Captain Cook had been directed to search for the 'great south land' thought to exist in the South Pacific Ocean," Professor Moore said.
"This led to his charting Australia's east coast in 1770, and in 1788 to a British settlement at Botany Bay. Thus, European settlement of Australia is intimately linked to this 18th century scientific endeavour."
A century later, scientific expeditions were sent across Australia to observe the transits of 1874 and 1882, with many of these successfully recording the event.
Professor Drinkwater said that from a scientific perspective, transits of Venus had helped astrophysicists determine the Astronomical Unit - the distance between the Earth and the Sun.
"All our measurements of distances in the Universe are ultimately based on this measurement of the distance to the Sun," he said.
"Without this we wouldn't have any physical understanding of what lies beyond our own Solar System and we'd certainly have no idea that we live in an expanding Universe."
Professor Drinkwater and other UQ astronomers last year reported that mysterious "dark energy" was real and not a mistake in Einstein's theory of gravity.
"In recent years, there has been a great deal of scientific effort directed towards the search for planets outside the Solar System - known as exoplanets," Professor Drinkwater said.
"Planetary transits, like that of Venus, across distant stars are the main method used to search for these exoplanets."
Venus will take about six-and-a-half hours to travel across the face of the Sun on June 6. Australia is one of the best places on Earth from which to observe the transit, with the entire event visible from eastern and central parts of the continent.
Professor Drinkwater said there were four key times during the day in Brisbane that people would be most interested in watching the Transit of Venus:
8:16am - Venus first touches the Sun
8:34am - Venus just inside the Sun on the way "in"
2:26pm - Venus just inside the Sun on the way "out"
2:44pm - Venus last touches the Sun