Sky watchers in parts of Canada and the U.S. were treated to the Northern Lights this week. The phenomenon is also known as the Aurora Borealis.
It's caused by something called a coronal mass ejection or CME.
Gina Ressler, a meteorologist at The Weather Network, says that a CME occurs when the sun spits out a burst of charged particles.
"As those charged particles track near the earth, they interact with our magnetic field -- and that's what creates the burst of colours," she explains.
NASA says the CME hit Earth's magnetic field last weekend. CME's can also affect electronic systems in satellites and on the ground.
While we often see the lights dance across the sky in shades of red, green or blue, sometimes they are just white.
“That's because the colour level is so low that our eyes can not detect the colours,“ says astronomer Andrew Yee. “But if you take a picture with a camera, you will see all these different colours then."
The best places for seeing the Aurora Borealis or the Northern Lights, are in communities away from city lights and with a good view of the northern sky.