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The Debunker: Are Sunspots Dark?

by Ken Jennings

Take a break from your fun in the August sun to ask yourself: what do I really know about this giant glowing globe of plasma shining down on my picnic/game of Ultimate Frisbee/clothing-optional beach right now? Given that the Sun is what makes life on Earth possible, it's appalling how much misinformation we've been fed about our nearest star. Speaking of our nearest stars: Ken Jennings, that one guy from Jeopardy!, may not be as bright as the Sun, but he's an expert on debunking myths and misconceptions. All month, he'll be lighting up our stellar misconceptions regarding the sun.

The Debunker: Are Sunspots Dark?

You've probably seen images of sunspots, patches on the face of the Sun where strong magnetic fields are keeping the Sun's normal convection in check. As a result, less energy flows from the Sun's hot interior up to the photosphere, and we get those cool, dark spots—almost black, in the NASA photos you're probably picturing. The effect on the "solar weather" is noticeable enough that some scientists have linked sunspots to climate changes on Earth.

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But this is yet another case where the one thing everyone knows about sunspots—that they're cool and dark—couldn't be more wrong. Even the chilliest sunspot has a temperature of about 3700 ºC, hot enough to melt stainless steel. And "dark"? Not remotely. A sunspot in the night sky would still be over ten times brighter than the full moon, and glow with a piercing red-orange light.

Why do sunspots appear dark, then? Only by comparison. The blindingly bright photosphere of the Sun is the only place a sunspot would ever look dark, sort of like how the most stupefyingly attractive "10" in Enid, Oklahoma can become an "8" or a strong "7" overnight just by moving to New York or L.A. Sunspots are still hot enough to liquefy any material known to man—so if NASA is planning to land a rocket on the Sun, sunspots aren't going to be much help. As the old joke goes, we'll just have to try going at night.

Quick Quiz: What hit by The Police was inspired by Sting's now-wife Trudie Styler, who commented to him during a 1983 trip to Jamaica, "Look, there's a little black spot on the sun today"?

Ken Jennings is the author of six books, most recently his Junior Genius Guides, Because I Said So!, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at ken-jennings.com or on Twitter as @KenJennings.