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Transit of Mercury - November 2006

Transit of Mercury
Photo: NASA

Never look at the Sun directly, unless you place a specially designed filter in front of your eyes. You could permanently burn your retinas!

The Transit of Mercury, November 8, 2006

A rare astronomical event will take place on November 8: Mercury will pass directly between the Earth and Sun. For several hours, the planet will appear silhouetted against our daytime star. Due to unfavorable weather, observation of the Nov. 8 transit of Mercury will not be possible from Montreal. All observation activities are cancelled.

The phenomenon

Mercury is the closest planet to the Sun. Its orbit is therefore much smaller than Earth's: While our planet circles the Sun in one year, Mercury completes its orbit in only 88 days.

Every 116 days on average, Mercury catches up to our planet and passes between the Earth and Sun: This is known as inferior conjunction. Normally though, Mercury’s orbit, which is tilted 7° with respect to that of Earth, carries it either above or below the Sun’s disk. But on rare occasions, when the inferior conjunction occurs in early May or early November, Mercury’s alignment carries it directly in front of the Sun. This is called a transit. On average, there are 13 transits of Mercury per century, but not all of them are visible from any given place.

Transits of Mercury, and even more so those of Venus, have greatly influenced the history of astronomy. Indeed, astronomer Edmund Halley figured out a way to use these events to measure the actual distance between the planets, and from there, the distance to the stars. For all practical purposes, however, Mercury is too small to provide accurate measurements, and so 18th and 19th century astronomers focused their efforts on the very rare transits of Venus. See our special report on the June 2004 transit of Venus for more information.

Today, the distance to the planets is measured with great precision thanks to radar. The transits of Mercury and Venus are now of interest only because they are rare, and because of the history they evoke.

Transit 2006

On November 8, 2006, Mercury will cross the Sun’s disk in a little less than 5 hours. This transit will be visible in its entirety in the Pacific and on the West Coast of Canada and USA. In the eastern portion of North America and in South America, observation of the transit will be interrupted by sunset.

In Québec, only the first half of the transit will be visible. Tiny Mercury will take just under 2 minutes to cross the edge of the Sun, from 14:12:22 to 14:14:15 EST (contacts 1 and 2, respectively). The Sun will then be about 18 degrees above the horizon. (For locations farther from Montreal or Québec City, the actual contact times could vary by a few seconds.)

Sunset will bring an end to the observation of the transit: around Québec City, it will occur about 16:15 EST; in the Montreal area, the Sun will set around 16:30 EST, just a few minutes before maximum transit, scheduled around 16:40 EST.

If you miss this transit of Mercury, the next one will occur on May 9, 2016, and it will be visible from beginning to end from Québec. But before that one, there will be a transit of Venus on June 5, 2012…


During the transit, Mercury will appear like a tiny black dot measuring about 1/194th of the Sun’s diameter — too small to be visible without magnification.
In order to fully appreciate the event, it will be necessary to use a telescope fitted with a special solar filter and capable of a minimum magnification of 50 to 100 power.

The Sun’s image can also be projected on a screen with a pair of binoculars or small telescope. In this case, a filter should not be used. However, the setup must be monitored at all times to ensure that no one accidentally looks through the optics. Under all circumstances, please follow the tips and techniques on how to safely observe the sun for a safe and enjoyable observation of the transit.


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