Shy Venus in rare Sun crossing next month

Last chance to see until 2117 has exoplanet-spotters excited

Ultraviolet image of the Venus southern hemisphere

Venus will pass across the face of the Sun just four weeks, the last chance for more than a century to observe our nearest planetary neighbour crossing our star’s fiery surface.

Known as a “transit of Venus” the event will take place on June 5th and 6th. The last transit took place in 2004, but the next is not due until 2117.

This transit will be visible to most Reg readers, with its early moments appearing in the North American sky and the conclusion visible to Europe. Vulture Central APAC, The Reg’s new Sydney eyrie, will get the best view of the full event. A terrific map showing just who gets to see what, and when, is available here.

As is the case with solar eclipses, you’ll do your eyes in staring at the Sun during the transit. Numerous webcasts will therefore be available to spare your, or you can tool up with special glasses like these from Astronomers Without Borders. Inevitably, there’s also an app for this, on iOS and Android.

This year’s transit will be of special interest to exoplanet spotters, as one of their favourite ways to find far-off planets is to measure the brightness of stars. Transits dim a star’s output just enough to suggest planets’ presence in a remote star system. The chance to observe a transit at such close cosmic quarters is therefore eagerly anticipated as a likely source of data that will help refine this method of planet-spotting.

Transits are also much-anticipated due to their historical significance. The voyage on which Captain James Cook’s mapped Australia and New Zealand had, as its first mission, observation of a transit from Tahiti. Both nations therefore attribute their eventual colonisation, in part, to transits. Sir Edmund Halley, of the eponymous comet, used the 1676 transit to accurately measure the distance between the Earth and the Sun. ®

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