The Sun’s atmosphere is way, WAY hotter than its surface — here’s why

The visible surface of the Sun, or the photosphere, is around 6,000°C. But a few thousand kilometers above it – a small distance when we consider the size of the Sun – the solar atmosphere, also called the corona, is hundreds of times hotter, reaching a million degrees Celsius or higher. This spike in temperature, despite the increased distance from the Sun’s main energy source, has been observed in most stars and represents a fundamental puzzle that astrophysicists have mulled over for decades. In 1942, the Swedish scientist Hannes Alfvén proposed an explanation. He theorized that magnetized waves of plasma could carry huge amounts of…

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