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A tiny dot of the planet Venus is seen on the northwest side of the Sun's disc as viewed in Manila, Philippines, on a rare astronomical occasion in this June 8, 2004 file photo. On June 5, 2012, Venus will pass across the face of the sun, producing a silhouette that no one alive today will likely see again. Transits of Venus are very rare, coming in pairs separated by more than a hundred years. This June's transit, the bookend of a 2004-2012 pair, won't be repeated until the year 2117. Fortunately, the event is widely visible. Observers on seven continents, even a sliver of Antarctica, will be in position to see it. (BULLIT MARQUEZ/AP)
A tiny dot of the planet Venus is seen on the northwest side of the Sun's disc as viewed in Manila, Philippines, on a rare astronomical occasion in this June 8, 2004 file photo. On June 5, 2012, Venus will pass across the face of the sun, producing a silhouette that no one alive today will likely see again. Transits of Venus are very rare, coming in pairs separated by more than a hundred years. This June's transit, the bookend of a 2004-2012 pair, won't be repeated until the year 2117. Fortunately, the event is widely visible. Observers on seven continents, even a sliver of Antarctica, will be in position to see it. (BULLIT MARQUEZ/AP)

Planetary parade

Venus, Earth and the Sun align in rare event Add to ...

The upcoming transit of Venus provides a unique opportunity for scientists to double-check this planet-hunting technique.

“Venus is similar in size to the earth. And so it is a perfect example of an earth-like planet travelling in front of a sun-like star – which is just what we are looking for out there,” said Terence Dickinson, editor of SkyNews, a Canadian-based astronomy magazine.

However, Hubble can’t be pointed directly at the sun which would fry its instruments. Instead, it will focus on the moon which will act as a mirror to collect reflected sun light. A tiny fraction of this light would have passed through Venus’s atmosphere. By analysis these rays, scientists hope to see the chemical signatures of Venus’s atmosphere which is well known from the robotic space probes. This approach mimics how scientists are trying to sample the atmospheres of worlds outside the solar system.

“It will be a great test case to understand whether we are doing it correctly,” noted James Graham, director of the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto.

What’s truly amazing is the sensitivity of today’s telescopes, which can detect the slightest changes in light. The Transit of Venus will dim the sun by less than 1 per cent.

HOW TO WATCH THE TRANSIT

For sky watchers in Canada, the Transit of Venus will start late on Tuesday afternoon. But the sun will set while Venus’s six-hour trek is still in progress. Only those in the far northwest will have a chance to witness the entire celestial show.

You’ll need a solar filter or specialized glasses – the same type used for viewing an eclipse – to protect your eyes from the sun’s potentially damaging rays. A pair of transit glasses is available with each newsstand copy of the May/June issue of SkyNews.

Many educational institutions and local branches of the Royal Astronomical Society of Canada will be hosting viewing sites where the public can look at the sun through special solar telescopes. For instance, the Astronomy and Astrophysics Department of the University of Toronto will be staging a show at Varsity Stadium, starting at 5:30 p.m. (Pre-register at universe.utoronto.ca/transit2012/)

Of course, you’ll also need relatively clear skies. Dr. Roy Bishop, a retired professor of physics at Acadia University, had hoped to see the transit in 2004. He set up his telescope on the shores of the Bay of Fundy, not far from his home in Avonport, N.S. But thick clouds blocked the view.

“I was certainly disappointed, although I thought there was a good chance I would be alive in eight years and have another crack at it,” said Prof. Bishop. He is now monitoring weather forecasts. And, if need be, he’s prepared to travel to a spot that’s likely to have sunny skies.

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