Dear Ana,
When the northern lights come out, beautiful, colorful patterns stretch across the night sky. But they begin with a star that is millions of miles away: our sun.
Not only does the sun give us warmth and light, but it is also so full of energy that it can be outrageously explosive. These explosions often send tiny particles out to Earth. My friend Nic Loyd, a meteorologist at Washington State University, said this is called a “solar wind.”
We don’t always notice the arrival of the particles. Sometimes there are too many clouds. Or maybe it’s too bright out. The sunlight is a lot brighter than the northern lights.
“In other words, seeing them is a rare treat,” Loyd said. “And one must be in the right place at the right time.”
If you visited Alaska, Scandinavia, or Canada, the northern lights, which are also called the aurora borealis, would be quite a sight. But there are also southern lights, which are called the aurora australis. Since there aren’t as many people who live in Antarctica, most people go see the ones in the north.
The auroras happen around the north and South Poles because Earth is like a giant magnet. Scientists think that as Earth’s interior of molten metal swirls around with the spin of the planet, it helps generate a magnetic field. That’s why our compasses point in the general direction of the poles.
The magnetic field can help protect the planet, warding off the charged particles of the solar wind, but sometimes it is weak in spots. Those tiny particles that traveled from the sun make their way through. And those particles have an electric charge.
Electricity and magnets can interact with each other. The sun’s particles travel along the lines of the Earth’s magnetic field, so they end up concentrating around the North Pole and South Pole.
If the particles can get through the magnetic field, they’ll run into air. As you may know, our air is mostly made up of things like oxygen and nitrogen. When these particles smash through the atmosphere and hit oxygen, we see colors like green or yellow.
The element nitrogen produces red, violet, and sometimes blue. As you observe the northern lights, you may also notice that the altitude also affects colors. For example, yellowish-green happens about 60 miles above the Earth. Rare, red auroras can happen about 200 miles up.
Other planets in our solar system, such as Jupiter, also have auroras. The Hubble Space Telescope took pictures that show an aurora at Jupiter’s North Pole. It makes me wonder what it would be like to experience the northern lights of faraway places. If you are anything like me, maybe one day, you’d like see the northern lights here on our planet, too. Until then, keep on exploring and enjoy this light show.
Sincerely,
Dr. Universe