How to catch your once-in-a-lifetime look at Comet Leonard

Your once-in-a-lifetime chance to see a green comet named C/2021 A1 — a.k.a. Leonard — is here. Astronomy experts, including the comet's discoverer, offer tips on when and how to see the comet.

Like other comets, Leonard is a ball of frozen gas, rocks and dust. When its orbit brings it close to the sun, the heat causes some of that material to vapourize, which makes it glow and sprout a tail of gas and dust. 

While many comets pass through our solar system, few come close enough to the sun or the Earth for us to see them.

This week, it may be possible to see Leonard even without binoculars, the experts said.

"Brighter comets are rare, so it's definitely worth making an effort to see them," said Chris Vaughan, an operator at the David Dunlap Observatory in Richmond Hill, Ont., and a volunteer with the Royal Astronomical Society of Canada. Vaughan recently posted about Comet Leonard on his Astronomy Skylights blog.

Leonard's discoverer, Greg Leonard, has discovered 13 comets, but said this one feels "like hitting the celestial jackpot," because of how visible it will be. 

"It's a real dream come true and it's very, very humbling,"  he told CBC's As It Happens on Dec. 2.

Right now, the comet is visible in the Northern Hemisphere in the eastern sky to people using binoculars from anywhere in Canada in the early morning, he said. 

It's expected to get brighter and closer to the horizon every morning until Saturday, Dec. 11. 

For those who want to see the comet, Vaughan recommends going out in the early morning over the next couple of days, if the sky is clear. He said an area away from city lights, with a clear view of the horizon to the east, would offer the best view. By returning on subsequent mornings, you should be able to notice the change, he said.

If the weather co-operates, Friday and Saturday mornings around 6 a.m. may be the best bets for a good view. At that point, Vaughan said, Leonard should still be high enough that it won't be blocked by trees and houses or distorted by the atmosphere.  

On Sunday, Dec. 12, the comet should make its closest approach to Earth, then disappear the next day for Northern Hemisphere viewers.

It's expected to return Monday after sunset, as it heads away from the Earth toward the sun, getting fainter over the following weeks.

"But it'll never get very high above the horizon," Vaughan said. "The pre-dawn is your best chance [for viewing], the next few days."