On Thursday morning, a solar flare erupted from a sunspot on the surface of the sun. Radiation was hurled into space. As you read this, it is traveling toward Earth and will graze the planet's magnetic field tonight, causing a display of geomagnetic fireworks called the aurora borealis, or northern lights.
Watch the sky tonight about midnight, Colorado Mountain College astronomy professor Jimmy Westlake said.
For astronomers, the tension has been building for a week, ever since a giant sunspot rotated around the edge of the sun.
"It's been growing in size," Westlake said. "This is the biggest one in years. It's about as big as the planet Jupiter."
A sunspot is a magnetic storm that occurs on the surface of the sun.
"It's a powerful, tangled magnetic field that stores a lot of energy," Westlake said. "Then it snaps. It breaks like a twisted rubberband that has been stretched too far and sends radiation our way." When it hits Earth's atmosphere, it causes the sky to glow and move like bright curtains blowing in the solar wind.
But predicting auroras is like predicting rain or snow, Westlake said.
"They are giving us a 25 percent chance (of seeing auroras), which is pretty high for us. I've seen some brilliant auroras when there was only a 5 percent chance."
Tonight is the first time in more than a year and a half that auroras have been forecast to be visible in Routt County, and it will be the last chance for a while, he said.
"It's not a sure thing, but you should definitely be on heightened alert," Westlake said.
Anyone interested in seeing the auroras should get to a dark location with a good view to the north at about midnight.
When seen this far south, auroras tend to shine with reds and purples, unlike in Alaska, where they tend to appear green.
"The lights will dance and shimmer," Westlake said. "Before midnight, the curtains move to the west. After midnight, they move to the east."
For more information about the solar storm, visit spaceweather.com.
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