Jupiter-size exoplanets orbiting close to their stars have upended ideas about how giant planets form. Finding young members of this planet class could help answer key questions.
The June 2020 discovery of the exoplanet HIP 67522 b, which appears to be the youngest hot Jupiter ever found, will help. It orbits a well-studied star that is about 17 million years old, meaning the hot Jupiter is likely only a few million years younger, whereas most known hot Jupiters are more than a billion years old. The planet takes about seven days to orbit its star, which has a mass similar to the Sun's. Located only about 490 light-years from Earth, HIP 67522 b is about 10 times the diameter of Earth, or close to that of Jupiter. Its size strongly indicates that it is a gas-dominated planet.