Astronomers and enthusiasts alike are gearing up for a once in a lifetime opportunity to observe the planet Venus cross the face of the Sun, which will take place between June 5th and 6th for a period of seven hours. The phenomenon known as the Transit of Venus occurs in pairs eight years apart every hundred years or so, with the last one happening in 2004. Before then there was a transit in 1882 and the next one will be in 2117.
Despite ancient civilizations having a precise knowledge of Venus and the planet’s motions, there is no evidence to suggest that these cultures knew anything of its transits, and it wasn’t until the 17th century that Johannes Kepler predicted a transit of Venus occurring in 1631.
More than just a spectacular celestial event, the Transit of Venus also helped provide important astronomical data for scientists. These included making a well-informed estimate of the size of the planet, as well as accurately measuring the distance between the Sun and the Earth. There have also been other side benefits, and as UWS Observatory director Professor Miroslav Filipovic commented:
“Captain James Cook sailed to Tahiti to observe a pair of transits occurring in 1761 and 1769 and subsequently discovered the coast of Australia.”
Nowadays, a Transit of Venus is useful in learning more details about Venus’ atmosphere using techniques which, once honed, could be used to determine the atmospheric composition of faraway “exoplanets.” The Hubble Space Telescope will be fundamental in this process, although it will use the Moon as a mirror to observe reflected light to prevent its sensitive instruments from being completely frazzled.
In the same way, Earth bound human observers should take the same precautions used when observing solar eclipses, such as wearing eclipse shades or observing the event through a telescope with a solar filter.
North America will see the start of the transit in the afternoon and evening of June 5th, while Eurasia sees the end of the transit in the morning on June 6th.
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