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The Transit of Mercury, November 8, 2006

A rare astronomical 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.

LAST MINUTE: Due to unfavorable weather, observation of the Nov. 8 transit of Mercury
will not be possible from Montreal. All observation activities are cancelled.

Mercury transits the Sun. For a few hours on November 8, Mercury will appear as a tiny black dot in silhouette against the Sun. Contacts are the times at which the edges of the Sun and Mercury just touch.

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.

World visibility map of the transit of Venus

World visibility map of the 2006 Nov 8 transit of Mercury.
Courtesy of Fred Espenak, NASA/GSFC.

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 6, 2012…




Great care must always be taken when observing the Sun: Intense solar radiation can cause instantaneous burns to the retinas and permanent eye damage. When observing the Sun directly, either with the naked eye, or a telescope, one must always use specially designed solar filters.

Safe observing methods

In case of doubt, why not show up at one of the public observing sessions organized by amateur astronomers!

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 these tips and techniques for a safe and enjoyable obervation of the transit.

An invitation...

The public is invited to join the Montréal Planetarium astronomers, supported by volunteers from the Société d'astronomie du Planétarium de Montréal, to observe the upcoming transit of Mercury. Starting at 2:00 p.m. on November 8, and until sunset (weather permitting), telescopes will be set up at the west end of the parking lot of parc René-Lévesque, Lachine Borough, facing lake St. Louis. In case of rain or overcast skies, it will be impossible to observe the transit, and the event will simply be cancelled.

To get there, by car: from autoroute 20, take route 132 towards Mercier Bridge, and exit at rue Clément; turn right on Clément; turn left on St. Patrick; continue on rue du Canal to the far end of the parc René-Lévesque parking lot (metered parking).

To get there, public transit: from the Angrignon metro station, take bus route 110-Centrale (departures every 30 minutes; allow another 30 minutes to destination); get off at the corner of St. Patrick and Chemin du Musée, then walk 800 metres to the far end of the parc René-Lévesque parking lot.

More information...

The following websites are great starting points for more information on the transits of Mercury and Venus:

Site in English

Sites in French

See the transit LIVE on the Web


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Credits.  Last Modified: 2006-11-07