Hydrogen and helium are best known as the gases that make things float — from zeppelins to birthday balloons. Both elements are rare here on Earth — there’s even been a shortage of helium in recent years.

But there’s a huge supply of both elements just 93 million miles away — in the Sun. Together, they account for more than 98 percent of the Sun’s mass. And like most stars, the Sun has only a sprinkling of the heavier elements that are common here on Earth, such as oxygen, carbon, and neon.

Hydrogen and helium are the lightest and simplest of all elements. They were created in the Big Bang. Almost everything else was forged later — either in the hearts of stars, or in stellar explosions or mergers. These elements were scattered into space, where they could be incorporated into later stars, like the Sun.

Today, about 73 percent of the Sun’s mass is hydrogen, while most of the rest is helium.

When the Sun was born, those numbers were a little different. But the Sun’s core is hot enough to sustain nuclear fusion. Hydrogen atoms “fuse” together to make helium, releasing the energy that powers the Sun. So today, most of the core’s mass consists of helium, while the surrounding layers are still mostly hydrogen.

Fusion converts almost 700 million tons of hydrogen to helium every second. The Sun is so huge, though, that it won’t run out of fuel any time soon — it’ll stay in the prime of life for billions of years.

Script by Damond Benningfield

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