Galileo Gave the Northern Lights Their Name

Humans have been watching the dazzling dance of the northern lights for thousands of years; archaeologists believe some of the world’s prehistoric cave paintings, estimated to be about 30,000 years old, feature the colorful waves. However, their official name — aurora borealis — didn’t come about until more recently, when Galileo coined the term in 1619. The name is a combination of two ancient deities: Aurora was the Roman goddess of dawn, and “borealis” comes from Boreas, the Greek god of the north wind and winter.

Scientists Couldn’t Explain the Northern Lights Until the 1900s

Galileo believed sunlight reflecting in Earth’s atmosphere created the northern lights, and while he wasn’t correct, the 17th-century astronomer was right that the sun plays a role. In the early 1900s, Norwegian scientist Kristian Birkeland was the first to propose the idea that the aurora borealis is caused by electrically charged particles leaving the sun. Birkeland died in 1917, but his theory was later proved accurate. In the decades to follow, scientists determined that as particles traveling from the sun’s outer layer hit Earth’s magnetic field at up to 45 million miles per hour, they collide with oxygen and nitrogen molecules in the atmosphere. This happens at the poles because the planet’s magnetic field deflects these particles around much of the globe, but the field is weakest at the poles, allowing some of the sun’s particles to penetrate the upper atmosphere. These microscopic crashes release bursts of light that we see as the northern lights.

There Are Southern Lights, Too

Auroras aren’t found only near the North Pole — they’re also on display at the planet’s southern tip. The aurora australis, aka the southern lights, occurs for the same reasons as the northern lights, and satellite images from space show they often look identical. However, scientists think that solar winds can skew the planet’s magnetic field and our view of the lights, twisting them into different shapes that don’t necessarily match each other.

The Northern Lights Most Commonly Appear Green

Auroras come in a handful of colors, but most of the time they appear in ribbons of green. Color is in part dependent upon where the sun’s incoming electrons meet the gases in Earth’s atmosphere; the green sheen is produced when charged particles collide with oxygen molecules at altitudes of 60 to 190 miles, while red auroras appear between 190 to 250 miles of altitude. Blue, purple, pink, and yellow — the least common colors — tend to be visible during periods of increased solar activity.

The Northern Lights Sometimes Make Sounds

Scientists have long dismissed claims that the northern lights produce sounds, but recordings of the phenomenon from Finland prove that the auroras do occasionally produce noise. While the northern lights are predominately a silent phenomenon, they’re accompanied by hisses, whistles, and cracks about 5% of the time. Researchers believe the sounds are created when static electricity is released due to the auroras’ disturbances in the planet’s magnetic field.

The Northern Lights Are Constantly Occurring

We can’t always see the northern lights thanks to daylight, but they’re always flickering in the sky, because solar wind consistently blows toward Earth. Getting a good glimpse of the auroras requires darkness, not to mention being closer to the poles. Solar activity tends to peak around the vernal and autumnal equinoxes, making the polar lights easier to spot at those times, though geomagnetic storms can make the aurora borealis visible in unexpected spots, including parts of the U.S. (even as far south as Virginia), at other times of the year too.

There’s a Comet With Its Own Version of Northern Lights

Earth isn’t the only planet to experience auroras — Mars, Jupiter, Saturn, Uranus, and Neptune all have their own versions of northern lights. In 2020, NASA scientists also shared images of a comet that has its own aurora, a phenomenon never before witnessed. Images captured by the Rosetta spacecraft, which orbits the 67P/Churyumov-Gerasimenko comet, revealed the ultraviolet glow, and are undergoing further analysis so that researchers can learn more about solar winds.

The Northern Lights Will Be At Their Brightest Soon

The sun’s solar winds follow a predictable 11-year pattern, featuring lulls that cause less vibrant lights, or geomagnetic storms that push more energy toward the planet. During those peaks, the northern lights more vividly color the sky. The last peak (also called a solar maximum) occurred in 2014, and the next one is due to occur in 2024 or 2025. NOAA has an aurora forecast website that can help predict where to see the glow. You’ll probably need to head out of urban areas unless the lights are spectacularly bright.

A Space Probe May Help Us Better Understand the Northern Lights

NASA launched the Parker Solar Probe in August 2018 with the goal of better understanding the sun and its impacts on Earth. About two and a half years after it launched, the spacecraft became the first to touch the sun when it entered the star’s corona (aka the outer atmosphere).

During its seven-year life span, the Parker Solar Probe will orbit the sun 24 times, collecting data on how its charged particles flow toward Earth. This information could help scientists better understand how space weather impacts our satellites, power grid, and even the aurora borealis.