Last week, the Northern Lights, also known as the Aurora Borealis, lit up the skies above Estonia and much of northern Europe. The phenomenon will be more visible from Earth until 2025 when the sun reaches the peak of its current 22-year activity cycle, said Estonian astronomer Tõnu Viik.
"Consequently, there's hope of seeing, at least for the next few years, even more Northern Lights," he said on "Vikerhommik" on Monday.
"Auroras are the result of the Sun not being a yellow disc in the sky, but an active celestial body," said Viik. As various processes take place on the Sun's surface, a stream of charged particles is ejected, so-called solar wind. "These are usually protons and electrons. Once they reach the Earth, after a couple of days or so, then all the activity starts," the astronomer explained.
When viewed from Earth, the lights can be seen best at the magnetic north and south poles. Despite their beauty, they can sometimes cause problems for humans if there is too much activity.
"For example, in 1989, a large part of the Canadian power grid went down because of them. They ionized the entire surrounding area and as a result, part of Canada was without electricity for nine hours," Viik said, highlighting one example.
The Northern Lights are best seen at night as the human eye cannot spot them in the daytime. Viik said a cloudless night and the darkest possible observation spot are important factors when trying to see the lights.
"The most important thing is to choose a place where there is no additional light: houses, illuminated highways or whatever," he said.
He said the color of the aurora – such as green, purple, pink, or red – depends on the height of the solar wind hitting the Earth's atmosphere.
They are most visible in spring and autumn because the skies are clearest at these times of year.
But it is not worth hoping to see the lights on every clear night, as they are tied to the activity of the Sun.
"If there's already some activity on the Sun, such as a solar flare, there's a good chance that in two days' time the solar wind will be with us and the auroras can be seen," he explained.
Editor: Airika Harrik, Helen Wright