Relatedly, astronomers may have just pushed the upper size limit of what counts as a planet.

A distant star system with four super-sized gas giants has revealed a surprise. Thanks to JWST’s powerful vision, astronomers detected sulfur in their atmospheres — a chemical clue that they formed ...

Gas giants are large planets mostly composed of helium and/or hydrogen. Although these planets have dense cores, they don't have hard surfaces. Jupiter and Saturn are the gas giants in our solar ...

The Earth grew by the collisional accretion of tens of Moon- to Mars-sized planetary embryos, themselves formed from the collisions of many smaller rocky bodies. The interiors of these planetary ...