It always catches us by surprise to notice how fast the seasons change here. At this time of the year the change is unbelievably rapid and in such a short time the nightless night turns into dark nights, allowing the thousands of stars on the sky to escort our way. It’s not only the starry skies we’re in the search of on the dark autumn nights, but this is also the time when the Northern Lights start to conquer the sky, giving their first appearances of the approaching winter season. Therefore, it’s time to have a look deeper into the science behind the Auroras to fully understand where they originate from.
It’s easy to understand how legends and tales have been born in far-north countries when colossal sheets of vividly colored curtains make their dance across the night sky. The Auroras in Earth’s Northern Hemisphere are called the Aurora Borealis. Their southern counterpart, lighting up the Antarctic skies in the Southern Hemisphere, are known as the Aurora Australis. The name Aurora Borealis, which was conceived by astronomer Galileo Galilei in 1616 after the Roman goddess of the dawn and the Greek word for the north wind, refers to the lights in the Northern Hemisphere. The best places to see the Northern Lights are in remote locations—far from cities and their light pollution— on cloudless and moonless winter nights.
When magnetic fields on the sun get twisted together, they create sunspots, and particles escaping from these sunspot regions create something called solar wind that stream away from the sun at speeds of about 1,6 million kilometers per hour. After traveling 150 million kilometres to the Earth, the solar wind is lured by the magnetic North and South Poles. Around the Poles the magnetic fields are weaker, allowing the electrons to enter the Earth’s upper atmosphere where they’ll encounter atoms of oxygen and nitrogen at altitudes from 50 to 300 kilometres above the Earth’s surface. A shade of greenish-yellow, the most common color visible during one of these light shows, is caused by solar particles colliding with oxygen in lower altitudes—up to 240 kilometers above us. A collision with oxygen at very high altitudes, over 280 kilometers above the Earth, produces much rarer shades of red. A pinkish-red at the lower edges of the sheets of light is common, created by collisions with nitrogen particles.
The sunspots and solar storms that cause the most magnificent displays of the Northern Lights occur roughly every 11 years. The solar cycle peaked in 2013, but it was the weakest solar maximum in a century. Since record-keeping of the ebb and flow of the sun’s activity began in 1749, there have been 22 full cycles.
Did you know that the Auroras are actually not unique just to the Earth, but they also occur on other worlds in our solar system. Jupiter, Saturn, Uranus and Neptune each have thick atmospheres and strong magnetic fields, and each have their own Auroras — although these Auroras are a little different from Earth’s, given they are formed under different conditions. Back on Earth, the closer to the Poles you are, the better chances of catching this curtain or ever-changing colours on the sky you have – making Finland one of the top locations to cross the Northern Lights from your bucket list.
Unbelievable, don’t you think? The Sun, located 150 million kilometres from Earth, can create something that has us gasping for admiration and wonder. But, that’s enough of the science. As the winter approaches, we’ll take you on a journey to the minds of our ancestors who had no scientific explanation available for the marvelous lightshows on the dark night skies. Stay tuned to learn what kind of tales they built around the Northern Lights!