Why the northern lights are showing up in unexpected places

No matter how many times you see them, the northern lights, or aurora borealis—and their Southern Hemisphere equivalent, the aurora australis—are an ____________, breathtaking sight. Dancing silently in Earth’s upper atmosphere, they form iridescent sheets of green and red (or sometimes blue and purple) light.

In fact, both northern and southern lights are caused by the interaction of gases in Earth’s atmosphere with the solar wind: a stream of electrically charged particles, called ions, that shoot out from the sun in all directions. An aurora's colors signify where in the atmosphere, and with which gases, all of this is happening.

Auroras have been __________ on every planet in the solar system except Mercury—even, as with Venus and Mars, when the magnetic field is very weak or nonexistent. They have even been detected on a huge “rogue planet” 20 light years away. And astronauts have taken spectacular photographs and video of Earth’s auroras from the International Space Station.

Some years see more auroras than others. Sunspot activity waxes and wanes on an 11-year cycle; the most recent upward trend began in 2019 and will peak in 2024 or 2025. On September 1, 1859, astronomers had been watching a growing number of sunspots develop on our star’s surface when a solar flare sped toward Earth, creating vivid aurora displays as far south as Cuba and as far north as Santiago, Chile. Having never seen them before, some observers believed the bright lights ________ the end of the world, or that “it appeared as if there was a colossal fire on earth which reflected its flames on the heavens.”

(Fonte: National Geographic. — adaptado.)