On May 9, between 7:13 a.m. and 2:42 p.m., observers in Québec will have a chance to witness an unusual astronomical phenomenon when Mercury passes directly between the Sun and the Earth. As the planet’s silhouette reveals itself in front of the surface of our star, Space for Life invites you to join astronomy fans and observe the event together. (To fully enjoy the show without endangering our eyesight, the use of a telescope equipped with a filter designed specifically for observing the Sun is essential.) Such transits take place on average just 13 times a century, and this year it will be completely visible from Québec: a first since 1960. Observing conditions look promising — so join us!
A very specific observation timetable
In Montréal, the event will begin very precisely at 7:13:27 a.m., Eastern Daylight Time, and it will take Mercury’s tiny disk three minutes and twelve seconds to cross the edge of the Sun. Then, throughout the day, it will be possible to track the planet’s progress against the backdrop of the Sun. At maximum transit, Mercury will be two-thirds of the way between the edge and the center of the Sun; the time at that exact moment will be 10:57:47 a.m. As was the case with its entry, the planet’s departure will last for just over three minutes, ending at 2:41:19 p.m.
Mercury is not easy to spot against the surface of the Sun. To detect its tiny round black silhouette, it is absolutely necessary to use an optical instrument that magnifies 50 to 100 times, equipped with a filter especially designed for safe solar observation.
The Planétarium Rio Tinto Alcan team and the volunteer members
A rare phenomenon
Mercury is the closest planet to the Sun. Its orbit is therefore much smaller than the Earth’s. While the Earth completes a revolution around the Sun in one year, Mercury takes only 88 days to do the same. Every 116 days, on average, Mercury’s orbit takes it between the Sun and the Earth: that moment is called inferior conjunction. In general, the planet passes well above or below the Sun, because its orbit is inclined by seven degrees as compared to the Earth’s. But on rare occasions, when inferior conjunction takes place during a window of a few days in early May or November, the alignment is such that Mercury slips directly in front of the disc of the Sun: this is a transit.
Transits of Mercury, but above all those of Venus (much rarer), have highlighted the history of astronomy, because careful observation of these events has served to establish the exact scale of distances between planets in the solar system — and from there, the distance to the stars. Today the distance from the Earth to the planets is measured with great accuracy (within approximately one meter) thanks notably to radar echoes. Interest in transits of Mercury and Venus therefore stems above all from their rarity.
IMPORTANT WARNING — ATTENTION! CAUTION!
Consult the Space for Life website for more information about the phenomenon and advice on safe observation: espacepourlavie.ca/en.- 30 -