“It’s just another kind of neat experience, something that is rare and you don’t normally get a chance to do,” says Randy Attwood, executive director of the Royal Astronomical Society of Canada. The group’s local branches will be holding public viewings of the event across the country.
This particular Mercury transit has great timing — Mercury will appear as a tiny dot on the east side of the sun at 7:12 a.m. ET and slowly cross it over 7½ hours, disappearing on the west side of the sun at 2:42 p.m. ET. That will make the entire event visible from most of Canada — with the proper equipment, of course.
The event lasts so long that you have a good chance of catching part of it even if it’s cloudy for part of the day.
Attwood says this will be a great opportunity for people who have never seen Mercury before — and that’s probably most people.
The closest planet to the sun is generally hard to see, even at night, because it only appears close to the horizon just before sunrise or just after sunset, and you really need to know where to look.
Of course, you won’t be able to see Monday’s Mercury transit with your naked eyes and you shouldn’t try, warns Attwood, because looking at the sun directly will damage them.
In past centuries, transits of Mercury gave astronomers the rare opportunity to measure its apparent size and helped them estimate the distance between the Earth and the sun, NASA says. Today, they can help scientists calibrate instruments such as the solar-observing space telescopes Solar and Heliospheric Observatory, Solar Dynamics Observatory and Hinode.
Looking for transits of planets in front of stars in other solar systems is now the main technique used to find such distant planets, Delaney said: “Here you have the opportunity to see exactly in real time in our own solar system what we are doing to find exoplanets around other stars.”
Even though Mercury orbits the sun once every 88 days, its orbit is tilted relative to Earth’s orbit. That means most of the time, when it passes between the Earth and the sun, it appears to move either above or below the sun rather than in front.
That’s why Mercury transits happen so rarely, and only in May and November, Attwood said. This year, we’re lucky.
“There hasn’t been a transit in May in a while, and of course the weather is so bad in November,” he said.
The last Mercury transit was in 2006, and the next one will be in 2019. Then next two after that take place during our night, so if you miss the 2019 transit, you won’t have another chance until 2049.