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Credit: Patricia Klein.

Definition: These are gas giants that have a similar size to Jupiter or Saturn (heavier than about 100 times the mass of Earth). They are primarily composed of hydrogen and helium.

Hot Jupiters

Hot Jupiters are exo-Jupiters that are close to their stars and therefore receive a lot of energy from it (thus they are hot).

Hot Jupiters usually orbit their stars in just a few days (as opposed to one year for Earth, or even 87 days, for Mercury). They can have outside temperatures of more than 1000°C.

This type of planet is easier to observe with the transit and radial velocity method than other types, and thus were among the first to be found.

Example: 51 Pegasi b

Credit: Patricia Klein.

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