What is the Sun made of?
The Sun is made mostly of hydrogen, about 73 percent by mass, and helium, about 25 percent. Small amounts of oxygen, carbon, iron and other elements make up the rest.
The Sun is not solid, liquid or ordinary gas. It is made of plasma, a hot state of matter in which atoms have lost some of their electrons. Its density increases toward the center, where the core is much denser than lead.
In the core, at about 15 million degrees Celsius, hydrogen nuclei fuse into helium. Every second, the Sun turns about 4 million tonnes of matter into energy. This energy slowly travels outward and escapes as sunlight.
How we know
Scientists learn what the Sun is made of by splitting its light into a spectrum. Each element absorbs light at specific colors, leaving dark lines. In 1868, astronomers found lines that matched no known element, and they named it helium, after the Greek word for Sun. Helium was found on Earth only years later.
Did You Know?
The Sun contains about 99.8 percent of all the mass in the solar system. Jupiter makes up most of the rest.