A special event is currently underway in the skies, as the solar system's smallest planet of Mercury makes a rare, visible transit across the sun.
From 7:12 a.m. until approximately 2:45 p.m. ET, stargazers will be able to see Mercury as a small black dot silhouetted against the sun.
The reason why the event is rare comes down to gravity and elliptical orbits. A solar year lasts only 88 days for Mercury, but because the planet鈥檚 orbit is inclined several degrees differently from Earth, it's not every day that the sun, Mercury, and Earth line up perfectly.
In fact, says York University astronomy professor Paul Delaney, this is the first visible Mercury transit in almost a decade.
鈥淭his is a relatively rare event; it takes place only about 12 times a century,鈥� he told CTV鈥檚 Canada AM Monday.
鈥淭here will be another one in 2019, but after that, here on Canadian soil, you won鈥檛 actually be able to observe one again until 2049.鈥�
While the transit may not appear that exciting as just a black spot against the sun, Delaney says what鈥檚 mind-boggling is how fast the planet will be moving as it streaks past a sun that measures nearly 1.4 million kilometres across.
For astronomers, the event will allow them to learn a little bit more about Mercury, because even though stargazers have been watching Mercury and Venus transits for 400 years, there鈥檚 still much to learn.
鈥淪trange as it might sound, we鈥檙e still fine-tuning the orbit (calculations) of all the planets and objects in our solar system,鈥� he said.
Scientists for the , which is jointly operated by NASA and the European Space Agency, and NASA鈥檚 Solar Dynamics Observatory, or SDO, will work in tandem to study the transit. Louis Mayo, program manager at NASA鈥檚 Goddard Space Flight Center in Greenbelt, Maryland, said in a news release that, as celestial events go, this one is pretty fascinating.
鈥淎stronomers get excited when any two things come close to each other in the heavens,鈥� he said.
To catch a glimpse of the event, don鈥檛 even think about staring at the sun without eye protection. Not only will it damage your eyes, you won鈥檛 be able to spot tiny Mercury anyway. Instead, what鈥檚 needed is a telescope or binoculars fitted with protective solar filters.
For stargazers who don鈥檛 have access to such tools, the astronomy departments of many of the country's large universities will be hosting events, with some making telescopes available for use. Mercury's journey can also be seen on several live web streams, including off NASA's .
The forecast is good in most parts of Canada with clear skies unimpeded by clouds, says Delaney, so it鈥檚 an ideal day for sun gazing.
鈥淕rab it now, while you can,鈥� he said.
