Look up: 5 planets will align in Tuesday's night sky

Tonight, just after sunset, skywatchers across B.C. will be in for an eye-popping show.

Five planets — Mars, Uranus, Venus, Mercury and Jupiter — will be lined up in an arc and visible on the western horizon from almost anywhere on Earth.

"I like to call it, essentially, a cosmic coincidence," said Andrew Ferreira, a public relations representative with the Vancouver branch of the Royal Astronomical Society of Canada.

"It's purely just a coincidence that, you know, five planets happened to line up more or less from our perspective."

In an interview with CBC, Ferreira said the best time to view the phenomenon will be just after the sun drops below the horizon. Keeping watch just after sunset is best, because as the night sky moves, "it's essentially going to keep panning these planets down below the horizon."  

Ferreira's suggestion is to spot the half-moon in the sky and trace a visual line down from there to see Mars. Below that will be Uranus and Venus. Below Venus will be Mercury, and closest to the horizon will be Jupiter.

Ferreira said Venus will outshine Uranus, but Uranus will be visible as a "greenish-blueish glow." Mercury, he said, will be very faint but visible through binoculars, and people in downtown Vancouver or other urban centres might not be able to see Jupiter because of its low position on the horizon.

Getting away from city lights and buildings increases the chances for clearer viewing. Ferreira said giving your eyes a few minutes to adjust to the sky is also a good idea.

Great conditions for viewing

Of course, people hoping to catch the planetary procession will also benefit from clear skies overhead. And there's good news on that front.

"The forecast for almost the entire province is looking great for a night-sky viewing," said CBC meteorologist Johanna Wagstaffe.

"We have a high pressure system in place for B.C. which is bringing cloudless skies for almost everyone. The exceptions are a few high clouds that may sneak in tonight to northern B.C."

"It may get a little chilly though with no clouds to keep the daytime heat in, so bundle up when you look up tonight." 

Alignments happen once or twice each year

As for the rarity of planetary alignments, Ferreira said ones like tonight happen once or twice each year. But an alignment of all the planets in the solar system, minus Earth, "that's something like once every 200 or 300 years," he said. "So it kind of depends on the objects and how many of them are lined up."

Rare or not, Ferreira said events like tonight are always a joy, even for avid skywatchers like himself.

"It's exciting being able to tell people about it — to get other people excited about what we do," he said.

"I always tell people that astronomy is the easiest science to do because all you need is your eyes and the ground. You lie on your back and you look up and you know you're doing astronomy."