THE CORONAL HEATING PROBLEM
It may be one of the most familiar objects in the sky, but there is a persistent mystery surrounding our Sun: why is its outer layer so hot?
If you start in the core of our star and work outwards through it layers, the temperature continues to drop through the radiative zone and convective zone, out through its visible surface, the photosphere, to the darkness of space. But that’s where things get weird. The photosphere has a temperature of around 6,000 degrees Celsius (10,832 degrees Fahrenheit), but by the time you reach the corona – the Sun’s tenuous outer layer – it climbs again to several million degrees. This coronal heating problem has stumped astronomers for decades, and they’re desperate for answers.
The recently launched Parker Solar Probe could well help, as it will fly closer to the Sun that any mission before it. Living up close and personal with the corona could finally tell us why things don’t continue to cool the further you move from the core, the source of the Sun’s immense power.