Although the Sun’s power is most visible at and above its surface, its power originates deep within. Explore the processes that produce the Sun’s light, heat, and unpredictable storms.

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The Sun’s Energy

NARRATOR: The Sun has been shining brightly for more than 4 billion years. So, where does all that energy come from?

The answer starts with the Sun’s formation from a swirling cloud of gas and dust.

As gravity pulled matter together, intense heat and pressure began to break hydrogen atoms apart into protons and electrons—creating a high-energy mix of charged particles, called plasma.

As the Sun grew, the heat and pressure intensified to unimaginable levels.

LUC PETERSON (Princeton Plasma Physic Lab): And it’s under these extreme conditions that something really, really cool happens: nuclear fusion.

NARRATOR: Under the crushing power of gravity, protons in the plasma fuse together to form helium atoms, releasing a staggering amount of energy in the process.

The ongoing nuclear reaction inside the Sun is the same process that takes place inside a hydrogen bomb, only on a tremendous scale. We're talking 10 billion hydrogen bombs every second… for more than 4 billion years, and counting.

These nuclear fusion reactions, driven by heat and pressure, are the source of the Sun’s seemingly limitless energy.

But, with all that explosive force driving everything apart, how can the Sun possibly stay together?

LUC PETERSON: In the core of the Sun you’ve got this pressure from all of this fusion pushing outwards. And the Sun is huge so you have all this gravitational pressure pushing downwards. And so you’ve got gravity pushing down and the Sun trying to blow itself apart from the inside. And it is this beautiful balancing act between the two that keeps the Sun in one piece.

NARRATOR: If that were the end of the story, the Sun might really be the predictable glowing orb we once thought it was.

But, there’s another major force at play—one that makes our star far more dynamic and hard to predict: magnetism.


“Secrets of the Sun” National Geographic Television and WGBH Educational Foundation

ESO/M. Kornmesser


U.S. Department of Energy


Steven Bedard, Writer/Producer
Anna Rothschild, Animator/Editor/Narrator

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Sun 101 2 of 3

The Sun's Energy

Which two complementary forces keep the Sun from blowing itself up?