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We take the Sun for granted. It’s right there in the sky, blazing with the energy that keeps our planet warm. But how does the Sun shine? What’s going on inside?
As you probably know, the Sun is an enormous ball of hydrogen and helium, with a few trace elements thrown in. At the surface, the Sun is only about 6,000 Kelvin, but as you drop down within the Sun, the temperatures and pressures rise. By the time you reach the core, the temperatures are more than 15 million Kelvin. And the normally lightweight hydrogen has been crushed together with a density of more than 150 times the density of water.
At these pressures and temperatures, fusion can happen. Inside the core of the Sun, two atoms of hydrogen are combined to create helium-4 atoms. This process happens countless times every second. In fact, more than 600 million tons of hydrogen are converted into helium every second. The Sun converts the equivalent of the mass of the Earth every 70,000 years.
This releases an incredible amount of energy as photons. These photons are released and then absorbed by gas molecules. And this process happens millions of times during the lifetime of a photon. Amazingly, it takes time for this energy to get out of the Sun. A photon of energy generated at the core of the Sun can take 200,000 years to reach the surface. The light takes hundreds of thousands of years to get from the core to the surface, and then a mere 8 minutes to travel from the Sun to the Earth.
Just imagine if we could capture some of this energy. This article from Universe Today describes how we could capture some of this energy in space to make electricity, and another about how a blast from the Sun reached the outer solar system.
We have recorded an episode of Astronomy Cast just about the Sun called The Sun, Spots and All.
NASA Sun Earth Day