LTT 1445 Ac has a mass 1.37 times that of Earth and a radius 1.07 times that of Earth, making it the closest known Earth-sized exoplanet in our solar system. These numbers were calculated by matching LTT 1445 Ac transit data to its radial velocity.
Simply put, scientists can use an exoplanet’s transit data to calculate its radius. When a planet passes by its host star, the starlight dims and can be observed with a telescope.
Radial velocity, on the other hand, measures the wobble of the exoplanet caused by LTT 1445 Ac’s gravity. Studying an exoplanet’s radial velocity is used by scientists to determine its mass.