Saskatchewan sky watchers say the conditions are perfect for a vibrant show of aurora borealis starting on Friday night.

Local members of the Royal Astronomical Society of Canada (RASC) say by all indications the geomagnetic storm headed towards earth could potentially create one of the largest displays of aurora in history.

“Our sun is always active, but sometimes it becomes more active. And when it becomes more active, thats when we can get aurora,” said Ron Waldron, a Saskatoon-based member of the RASC and a retired public school teacher who now regularly travels to the north to teach groups about the phenomenon.

“Some solar activity produces things called coronal mass ejections, also known as a CME. And this week, several CMEs have erupted from the sun. Three or four to be exact. One of them was so strong, it literally caught up with the other three and has formed whats called a cannibal CME.”

When the solar plasma hurled from the sun collides with the earth’s magnetic field at the north and south poles, it causes the colourful aurora we see.

The ejections are coming from a giant sunspot — known by the not-so catchy title AR3664 — that was captured in a photo from Saskatoon on Thursday morning by Waldron’s fellow Saskatoon RASC member Mike Dolan:

Saskatoon sky watcher Mike Dolan took this image of the massive sunspot from Saskatoon on Thursday morning at 10:30 a.m., May 9, 2024. (Courtesy: Mike Dolan)

Sprawling almost 200,000 km from end to end, AR3664 is 15 times wider than Earth. You can see it through ordinary eclipse glasses with no magnification at all, Dolan said.

Dolan says the sunspot now “rivals the great Carrington sunspot of 1859” in size.

“The strongest aurora ever recorded, historically, was the Carrington event of 1859,” said Waldron.

“Carrington, an English man, was monitoring the sun through a telescope, and all of a sudden there was this huge flash. And within a few hours, the world was seeing aurora everywhere, and he sketched the sun spot. He wasnt able to photograph it, but he sketched it. And the sketch of the sunspot is very, very close to what is on the sun right now, he said.

The types of geomagnetic storms caused by coronal ejections are measured on a scale from Kp0 to Kp9.

Waldron, who goes to Norway and northern Manitoba every year to teach people about the northern lights, says the strongest aurora he’s seen in his life has been a Kp7.

He says this weekend’s event is predicted to be a Kp8.

“An extremely strong aurora, Friday night, Saturday morning,” said Waldron.

Both Waldron and Dolan say they plan to be outside with their cameras pointing north on Friday night, waiting for the show — although there’s no guarantee it will happen. Aurora science is “not exact,” says Waldron.

With the moon just a sliver in the sky on Friday, it shouldn’t be casting too much light in the way, and if you head away from the city lights, you’ve got a better chance of seeing it.

“If you get out of the city, it’s always better, for sure.”