Mercury visible in solar transit

The transit of Mercury past the sun will be visible as a dot passing in front of the solar disc for several hours this morning.

It will not be visible again from Australia for 26 years.

The curator of astronomy at the Sydney Observatory, Dr Nick Lomb, says the event can only seen about 13 times a century.

“This morning Mercury is seen directly in front of the sun, directly in the line between the Earth and the Sun,” he said.

“So we get a chance to see it moving as it circles the Sun and it is moving somewhat faster that the Earth is circling the Sun, so we actually see it moving.”

Dr Lomb says astronomers now use transits to improve models they use to discover planets outside our solar system.

“When astronomers are looking at distant stars, which are hundreds of light years away, and looking for very faint dips in brightness, they of course have no way of actually seeing the disc or even the planet itself,” he said.

“So they need to have the experience of observing a transit of Mercury, or a transit of Venus, to get an idea of what’s happening.”

Such rare events have fascinated astronomers for centuries – Captain Cook found Australia’s east coast while on a voyage to track the transit of Venus in 1769.

The event should only be viewed with your back to the Sun, via by a projection.