Walk carefully over to a fire and you’ll find it gets hotter the closer you get. As you walk away you start to feel cooler again. But if you were to do that at the surface of the Sun, the opposite would happen. You’d walk away from the intense heat, start to feel cooler and then suddenly begin to feel hot again. Moving far away from this hot source only puts you in the midst of an even hotter upper atmosphere. Although the Sun’s surface burns at a blisteringly hot 6,000 degrees Celsius (10,800 degrees Fahrenheit), the outermost layer of our host star’s atmosphere – which extends thousands of miles above the visible surface – reaches temperatures of around 1 to 2 million degrees Celsius (1.8 to 3.6 million degrees Fahrenheit). It’s a mystery that’s perplexed scientists around the world for decades. Just what is heating the atmosphere to such extreme temperatures? Numerous theories have emerged, each seeking to shed light on the corona’s physical properties and how they’ve come to be. But while the debate rages on, with a number of different promising ideas, astronomers may now be closer to an answer than ever before.
This solar puzzle has a name – the coronal heating problem – and was born in the 1940s. Astronomers had long been investigating the
