Venus to give stargazers once-in-a-lifetime treat as it crosses sun

By HELEN JOHNSTONE

Millions of people around the world will watch a once-in-a-lifetime event next month when the planet Venus, the Earth's closest neighbour, crosses the sun's path.

Scientists believe that on the evening of June 8 (NZ time), Venus will appear as a tiny speck at one side of the Sun and will slowly transverse the fiery ball for the next six hours.

A transit occurs when Venus and Earth, whose paths round the Sun tilt at slightly different angles, line up exactly where their orbits cross. No living person has seen a transit of Venus as the last occurred on 6 December 1882, during the reign of Queen Victoria. That was one of merely five events of its kind ever watched by man.

Only transits of Mercury and Venus are possible from Earth. On average there are 13 passages of Mercury each century. In contrast, transits of Venus occur in pairs, with more than a century separating each pair.

The transit can be seen from Europe, Africa and Asia. Other countries, including Japan and Australia, will be able to see the beginning of the transit, but the Sun will set before the event ends. None of the transit will be visible from New Zealand.

For millions the transit, which should only be watched through special glasses or by using telescopes to cast images of the sun on to white card or paper, will be a rare spectacle.

For space engineers, however, there is a more pressing interest as the event will provide a chance to test technology designed to question whether we are alone in the universe.

"In a few years, space probes and land-based telescopes will start to try to observe alien worlds in transit around other stars," said the Nasa scientist David Crisp.

"But first we need the Venus transit to test our techniques."

Professor Gordon Bromage, of Central Lancashire University, said the missions will try to detect tiny fluctuations in the light of other stars that are caused by planets passing in front of them. "Such transits only dim a star's output by a ten-thousandth of its total. We need to find out if we can detect that, and next month Venus will give us a perfect chance."

- INDEPENDENT