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The Sun’s core is the hottest part of the Sun.

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But our star’s temperature doesn’t behave as you might expect.

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The core is roughly 27 million degrees Fahrenheit

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and 10 times more dense than gold.

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As you move outward, the layers of the Sun become cooler and less dense.

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Something unusual, however, occurs when you reach the outermost layer.

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While the surface is around 10,000 degrees Fahrenheit,

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the corona – the Sun’s outer atmosphere — is several hundred times hotter.

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That’s the opposite of what happens with a fire, when it gets cooler the farther away you get.

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Scientists call this the coronal heating problem.

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It remains one of the greatest unanswered questions in astrophysics.

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The corona extends for millions of miles and continues outward as the solar wind,

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which bathes Earth and the entire solar system.

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This tenuous region consists of super hot elements such as hydrogen, helium, and iron.

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There are a variety of theories for what mechanisms could be adding that extra heat into the atmosphere.

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Scientists think it may be the result of the Sun’s convective motion

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that acts like boiling water and tangles magnetic fields on the surface.

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One theory suggests these tangled fields create small waves

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that push particles and heat from the surface into the atmosphere like how ocean waves push surfers.

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Another theory suggests small bomb-like explosions from the realignment of the Sun’s magnetic field create heat.

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Many scientists think it may be a mix of both.

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We’ve studied the corona from Earth and satellites,

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but to solve our star’s biggest mystery we have to make direct observations from the region itself.

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