The Transit of Venus is currently underway. The transit of Venus is when Venus passes between the Earth and the Sun and is visible as a small black dot on the Sun’s surface. This phenomenal event won’t happen again for another 105 years.
You can watch a live feed of the Transit at: Transit of Venus Australia 2012
What is a Transit?
A Transit of a planet occurs when the planet passes directly between the Earth and the Sun so that as seen from the Earth, the planet appears to pass across the face of the Sun. Transits can only occur with planets whose orbit is between that of the Earth and the Sun; that is, Mercury and Venus. A transit of a planet is similar to a solar eclipse but the planet appears to be much smaller that the Moon so it cannot cover the Sun and looks like a small black disc slowly crossing the Sun.
The Scientific value of Transits
The original benefit of observing transits of Venus was to assist in determining the Astronomical Unit. Later on, transits were used to examine Venus’s atmosphere using spectroscopy.
Currently there is a great deal of scientific effort directed towards the search for exoplanets (planets outside the Solar System) and planetary transits across distant stars are the main method used to search for them. The 2004 and 2012 transits of Venus are providing a valuable benchmark and comparison with a known planet transiting a known star.
Safe Viewing of the Transit
Never look directly at the Sun or you may cause serious and permanent damage to your eyesight. Damage can occur without any feeling that there is something wrong as there are no pain receptors in the retina and the damage may not become apparent for some time.