How are gas giant exoplanets born? James Webb Space Telescope provides new clues

A drawing of a planet that looks like Jupiter surrounded by rocky objects. It looks like rocks are impacting the planet from above. In the distance, there is a drawing of a blue sun-like figure with another Jupiter-looking planet around it.

Astronomers may have just pushed the upper size limit of what counts as a planet, thanks to new insights into how giant worlds form.

New observations from NASA's James Webb Space Telescope (JWST) suggest that even extremely massive gas giants — once thought too large to form like ordinary planets — may grow through the same basic process, shifting how scientists differentiate massive planets from brown dwarfs.