Exoplanet mass

The mass of an exoplanet is one of the most important characteristics for understanding what kind of world it is — whether it’s small and rocky like Earth or large and gaseous like Jupiter. Mass provides key information about the planet’s composition, gravity, and formation history.

Astronomers usually estimate a planet’s mass using the radial velocity method, which detects the tiny wobbles of a star caused by the gravitational pull of an orbiting planet. The stronger the wobble, the more massive the planet. In systems where both mass and radius are known (such as when transits are observed), scientists can also calculate the planet’s density, offering insight into its internal structure.

In the Stellar Catalog, smaller planets are listed in Earth masses, while larger planets are shown in Jupiter masses. Objects more massive than 13 Jupiter masses are classified as brown dwarfs — bodies that are more like failed stars than true planets.

Many of the exoplanets discovered so far are massive gas giants, as they are easier to detect with current techniques.