Giant Planets That Hug Their Stars: Meet Hot Jupiters
Our planet Earth takes 365 days to travel all the way around the Sun. But there is a kind of giant planet far, far away that zooms around its star in just THREE days! These amazing planets are called Hot Jupiters. They are huge — as big as Jupiter in our solar system — but they fly so close to their stars that they are sizzling, blazing hot.
What You Will Learn
In this lesson you will: - Learn what a Hot Jupiter is - Find out why Hot Jupiters are so incredibly hot - See how Hot Jupiters are different from our own Jupiter - Discover how scientists found the very first Hot Jupiter
What Is a Hot Jupiter?
A Hot Jupiter is a very big planet made mostly of gas — like a giant ball of clouds — that orbits extremely close to its star. Remember, an orbit means traveling in a big circle (well, more like an oval!) around a star. Earth orbits the Sun at just the right distance — not too hot, not too cold. But Hot Jupiters are much, much closer to their stars than Earth is to the Sun. Some Hot Jupiters are twenty times closer to their star than Mercury is to our Sun! That is why they get SO incredibly hot. The surface of some Hot Jupiters reaches over 2,000 degrees Celsius — hot enough to melt iron!
In 1995, scientists Michel Mayor and Didier Queloz discovered the first Hot Jupiter orbiting a star called 51 Pegasi, about 51 light-years from Earth. Everyone was shocked — no one expected to find a Jupiter-sized planet so close to a star! Their discovery won the Nobel Prize in Physics in 2019.
Why Are Hot Jupiters So Hot?
Think about sitting very close to a campfire. The closer you sit, the hotter you feel! Hot Jupiters work the same way. They orbit so close to their stars that they receive an enormous amount of light and heat every single moment. Many Hot Jupiters are also tidally locked — this means one side always faces the star (blazing hot!) and the other side always points away (much cooler and dark). It would be like if one side of Earth always faced the Sun forever and the other side was always night. No days, no nights — just permanent daytime on one side and permanent night on the other!
How Is a Hot Jupiter Different from Our Jupiter?
Our Jupiter is the biggest planet in our solar system. It is very far from the Sun — more than five times farther away than Earth! Because our Jupiter is so far away, it is very cold — about minus 145 degrees Celsius. Brrr! Hot Jupiters look similar to our Jupiter on the outside — they are made of gas and are very big. But they live in a completely different neighborhood: right next to their star, in a zone of intense heat. Think of it this way: our Jupiter is like a house on a nice cool street far from a bonfire. A Hot Jupiter is like a house built right next to the flames!
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How long does it take a typical Hot Jupiter to travel all the way around its star?
Why are Hot Jupiters so incredibly hot?
Draw Your Own Solar System With a Hot Jupiter
1. Get a big piece of paper and some crayons or markers 2. Draw a large yellow or orange circle near one side of the paper — this is the STAR 3. Very close to the star, draw a huge striped planet in red, orange, and yellow because it is SO hot — this is your Hot Jupiter 4. Draw a small dotted oval to show its orbit — keep it tight and close to the star 5. In the far corner of the paper, draw our own Jupiter in brown and white, very far from the Sun — show how different its neighborhood is 6. Label everything: Hot Jupiter, Star, Orbit, Our Jupiter, Sun 7. Show your drawing to someone and explain: Why is your Hot Jupiter hot? What would happen to you if you could stand on it?
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