You have probably heard of solar flares before. These bright eruptions from the Sun’s surface are triggered when knotted magnetic field lines within the Sun suddenly snap and reconnect, accelerating fireballs of plasma outward to distances up to 35 times the diameter of the Earth.

But have you ever heard of nanoflares?

In a study published yesterday in Nature Astronomy, a team of researchers led by Shin-nosuke Ishikawa of the Japan Aerospace Exploration Agency (JAXA) presented evidence that relatively small explosions called “nanoflares” may be responsible for the mysteriously extreme temperatures found in the Sun’s corona.

The solar corona — the outermost layer of hazy plasma surrounding the Sun that can be viewed during a total solar eclipse — has baffled astronomers for nearly 150 years. While the Sun’s surface only reaches around 5,500 kelvins, the corona can reach staggering temperatures of several million kelvins (1 million kelvins = 1.8 million Fahrenheit).