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Watch Monday's rare transit of Mercury anywhere

Scott Sutherland
Meteorologist/Science Writer

Monday, May 9, 2016, 6:28 PM - Skywatchers were in for a real treat on Monday, May 9, as a rare transit of Mercury took place across the face of the Sun.

Starting around 7:13 a.m. EDT this morning, a tiny dot showed up against the bright backdrop of the Sun's surface. This was the dark side of Mercury, the innermost planet of our solar system, as its orbit took it on a path directly between the Earth and the Sun.

SAFETY FIRST: Remember, never look directly at the Sun without the proper eye protection, and never point a telescope or binoculars at the Sun without using a proper solar filter. Witnessing these kinds of astronomical events is exciting, but not worth damaging your eyesight.

See a special view from space here.

Watch above, for an encore presentation of the Slooh Community Observatory online show, featuring views of the transit and guest appearances throughout the event.

Exactly how much of the transit you could see for yourself depended on your location. For the eastern half of Canada, the entire transit was visible, from when Mercury first touched the limb of the Sun until it passed completely out of the Sun's disk. In the western half of Canada, the transit was already in progress as the Sun was rising. Thus, the further west, the less of the transit was seen.

Newfoundland - entire transit visible, starting 8:43 a.m. and ending 4:10 p.m. NDT
Nova Scotia, New Brunswick, Prince Edward Island, Labrador - entire transit visible, starting 8:13 a.m. and ending 3:41 p.m. ADT
Ontario and Quebec - entire transit visible, starting 7:13 a.m. and ending 2:41 p.m. EDT
Manitoba - entire transit visible, starting 6:13 a.m. and ending 1:41 p.m. CDT
Saskatchewan - partial transit visible, starting 5:21 a.m. (sunrise) and ending 12:41 p.m. CST
Alberta - partial transit visible, starting 5:57 a.m. (sunrise) and ending at 12:41 p.m. MDT
British Columbia - partial transit visible, starting 5:39 a.m. (sunrise) and ending at 11:41 a.m. PDT

The view from space!

Although viewing an event like this for yourself is quite exciting, the very best view of this event were probably from space. From the vantage point of NASA's Solar Dynamics Observatory, the planet will trace a straight line across the face of the Sun, as shown in the video below:

To see more views from SDO, follow this link.

NASA also hosted a live-feed of the view from SDO, starting at 6:30 a.m. EDT on Monday. According to the SDO blog:

We will be providing a near-live feed of the SDO images of the transit at http://mercurytransit.gsfc.nasa.gov. The images are delayed a few minutes by the data delivery method, but our website will display the data as self-updating movies. The movies will include a visible channel and most of the EUV wavelengths. You pick the box and wavelength and watch the transit unfold!

Not only was this provide the clearest view, without the atmosphere in the way, it completely bypassed any inclement weather as well.

The disk of Mercury was very small against the full disk of the Sun, so some methods of viewing, such as using Mylar eclipse glasses, welder's glass (shade 14) or a pin-hole projector, wouldn't work. The best way to view it from Earth's surface was using a telescope with a special solar filter capping the end.

Since not everyone owns a telescope with special filters, the Royal Astronomical Society of Canada hosted several events at centres across the country.

Why are Mercury transits rare?

Even though Mercury only takes 88 days to orbit the Sun once, transits of this planet - at least ones visible from Earth - only happen once in awhile, with anywhere from 3 to 10 years in between. Very similar to the reason why we do not have solar and lunar eclipses every month, the rarity of a Mercury transit is due to the planet's tilted orbit. Thus, most times that Mercury passes between Earth and the Sun, it is either above or below the Sun's disk. Roughly 13 or 14 times each century, though, everything lines up just right.

The last Mercury transit before this one was on November 8, 2006. We only need to wait a little over three years for the next one, though, which will occur on November 11, 2019.


Editor's note: a previous version of this article listed an end time for the event in British Columbia at 11:41 p.m. PDT, rather than 11:41 a.m. PDT. This has now been corrected. We apologize for any confusion.

Watch below: Science@NASA presents the details of the May 9 transit of Mercury

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