How Hot Is the Sun? (2024)

Wonder of the Day #332

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SCIENCE — Earth and Space

Have You Ever Wondered...

How hot is the sun?
What is the sun made of?
Where is the hottest part of the sun?

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The sun that heats our planet and brings life to everything on Earth is a big ball of gas. Those gases are mostly hydrogen and helium, but the sun also contains small amounts of several other elements, including oxygen, carbon, nitrogen, magnesium and iron.

At its core, the sun burns millions of tons of hydrogen every second in a process called "nuclear fusion." Fusion turns hydrogen into helium and releases incredible amounts of energy in the process. It's fusion that creates the heat and the rays of light that eventually reach Earth.

How hot does it get where you live during the summer? Temperatures over 100° F are common in many parts of the United States during the summer.

Just think about how hot it would be, though, if Earth were closer to the sun. At 93 million miles away, the Earth is just far enough away from the sun to allow us to live comfortably all year long.

What's the hottest thing on Earth? Many people immediately think of lava, the hot, molten rock that occasionally flows from volcanoes.

Lava is indeed very hot, reaching temperatures of 2,200° F or more. But even lava can't hold a candle to the sun!

At its surface (called the "photosphere"), the sun's temperature is a whopping 10,000° F! That's about five times hotter than the hottest lava on Earth. But the photosphere isn't even the hottest part of the sun.

The sun's temperature gets even hotter as you move away from the photosphere — either inward toward the core or outward toward the sun's outermost atmospheric layer.

This outermost atmospheric layer is called the "corona." The corona is the bright halo of light you can see during a total solar eclipse.

The farthest point of the corona from the sun can be as hot as 3,600,000° F. That's right — 3.6 million degrees Fahrenheit. Incredibly, though, the corona isn't the hottest part of the sun either.

To get to the hottest part of the sun, you have to travel all the way to its core. In the core, the process of nuclear fusion creates temperatures of approximately 27,000,000° F. A temperature of 27 million degrees Fahrenheit is more than 12,000 times hotter than the hottest lava on Earth!

If the core is the hottest part of the sun, what's the coolest part? Occasionally, cool, dark areas of magnetic disturbances erupt on the photosphere.

Scientists call these areas "sunspots." Sunspots tend to be cooler than surrounding areas and are usually “only" about 6,700° F.

Wonder What's Next?

Ever wonder what life would be like on a spaceship? Find out tomorrowin Wonderopolis!

Try It Out

Whew! Today's Wonder of the Day really heated things up, didn't it? Well, we say pour it on! Let's get things even hotter as you explore one or more of the following activities with a friend or family member:

So how hot is hot? You'll need a thermometer for this fun exercise. Learn to gauge the temperature of various items from your own personal experience. You'll need samples of a few different liquids of different temperatures. You may want to get help from an adult, too, as this will be more fun if you use the stove and microwave to heat up some water. Find samples of various liquids, such as tap water at room temperature, milk from the refrigerator, the coldest water you can get from the tap, the hottest water you can get from your shower, some water that has been microwaved for 10, 20, 30 or more seconds, and some boiling water. Make a list of all of these items and your guess as to what temperature they are. Then use your thermometer to measure their exact temperatures. How accurate were your guesses? What was the coldest liquid? What was the hottest? How does the hottest liquid compare to the heat of the sun's core?
Now that you have a good idea how hot the sun is, it's time to think about how to protect your body from the sun's harmful rays. You should also know what to do if you do happen to get a sunburn. If you're going to be out in the sunshine, you should wear sunglasses and use sunscreen. This is especially true if you're going to be out in the sun for a long time, such as a day at the beach. Make sure you lather up with plenty of sunscreen and put more on every two hours. If you're exercising or sweating a lot, you'll need to apply sunscreen more often. Sunscreens come in many different varieties. There should be a Sun Protection Factor (SPF) number listed on the bottle. Try to use a sunscreen with an SPF of at least 15. The higher the SPF number, the more protection from the sun the sunscreen provides. If you're prone to sunburn, you might want to consider taking other steps to protect your skin. Wearing long-sleeved shirts, hats and sunglasses can help reduce your exposure to the sun. If you do happen to get a sunburn, there's not much you can do to make your skin heal quickly. The best thing you can do is treat your symptoms and give your skin time to heal. Keep your sunburned skin cool with damp towels or by taking cool baths. You should also keep sunburned areas moist by using moisturizing creams with aloe. Most drugstores carry special lotions to use for sunburns. If you find that you have a severe sunburn, you should consult a doctor. Signs of a severe sunburn include multiple blisters, as well as headaches and nausea. If you have just a few blisters, you probably don't need to see a doctor. Just don't break them. Breaking blisters slows the healing process and increases your risk of infection.
Up for a challenge? Earth is a comfortable place to live in our solar system, because of its distance from the sun. But what about life on those planets closer to the sun? Do some Internet research on your own to find out what life would be like on Mercury and Venus. What is their weather like compared to that on Earth? How hot and cold does it get? Could a human survive on those planets? Why or why not? Share your findings with your friends and family members.