Water Cooler: Sun science for kids

The heatwave we’re experiencing is a testament to how powerful our sun is. But how exactly does the sun produce all this heat?

The sun has been creating heat and light a lot longer than plants and animals have been around to enjoy it. Scientists estimate the sun is about 4.5 billion years old. Early human civilizations were well aware that the sun is what influenced the changing seasons, but how the sun worked remained a mystery for a long time.

The Greek philosopher Aristotle thought of the sun as a ball of ether, shining by itself without any need for fuel. In the 1600s, astronomers documented sunspots, which are dark spots on the sun’s surface. This led them to think that the sun might not be just light, but it might be made of matter that creates light. Matter is any substance that has mass and takes up space.

It turns out they were right. The sun is made of matter, just like the Earth, but what kind of matter?

Scientists were a bit confused. If the sun is made of matter, then how does it burn and glow for such a long period of time? After all, anything that burned on Earth eventually went out after it ran out of fuel, such as oil or a candle wick. To learn what keeps the sun shining, scientists needed to figure out what it was made of.

By the 1800s, scientists were aware that all matter was made of atoms. Atoms are the smallest unit of any matter, and this includes gases, solids and liquids alike. Even humans are made of atoms. Scientists around this time were also aware of elements, which are pure substances made up of only one type of atom.

Scientists eventually discovered that each element gives off a certain wavelength or type of light.

This meant that by studying the light of the sun, scientists would be able to figure out what elements make up the sun’s gases, which would give them insight into how the sun never goes out like a candle or a campfire.

One of the first scientists to study sunlight with this focus was Anders Jonas Ångström, a Swedish physicist. In 1862, he discovered that the most common element in the sun’s gases is hydrogen. This illuminated scientists to the idea that some of the elements found on Earth could also be found in the sun.

After this discovery, the commonly accepted belief was that the sun contains about the same proportion of various elements as the Earth does.

In 1925, a British-born American astronomer named Cecilia Payne-Gaposchkin published a paper explaining that the sun and other stars do contain some of the same elements found on Earth, but that they contain much more helium and hydrogen. Her findings were initially dismissed because she was a woman, but eventually it was accepted that she was correct.

Scientists later discovered that under the intense gravity in the sun’s core, the abundant hydrogen atoms were forced to join together in a process called thermonuclear fusion.

When this happens, hydrogen converts into helium and creates a huge amount of energy. It is such an efficient process and the sun contains so much hydrogen, that scientists estimate that over the sun’s 4.5 billion years, it has only used up about half of its hydrogen.

Inside the sun’s core, it is about 27 million degrees Fahrenheit. All that heat and energy travel throughout the entire solar system, creating the perfect conditions for life to exist on Earth, as well as some of those high summer temperatures.