A 3rd planet, just 1.5 times the size of Earth, may also be orbiting the star. ... The bottom graphic shows the relative sizes of the Kepler-18 and its known planets to the Sun and Earth.

On Feb. 22, 2017, scientists announced the discovery of TRAPPIST-1, an alien solar system with at least seven Earth-sized planets. See pictures of the discovery here.

These planets are about the size of Earth, and fall in the so-called “Goldilocks zone” of habitability, making them candidates to contain life.

This video starts with the Moon, runs through our solar system’s rocky and gas planets, and then takes us from our regular-sized Sun to the biggest hypergiant star, all to a pulse-pounding beat ...

TOI-6894 b, the largest exoplanet relative to its host star yet seen, doesn’t fit the most widely accepted formation model ...

In this artist’s conception, the sizes of the planets relative to the star have been exaggerated. Kepler-138 b, in the foreground, is likely an airless rocky world.

This illustration shows the seven Earth-size planets of TRAPPIST-1, an exoplanet system about 39 light-years away. The image shows the relative sizes of planets b through h, from left to right ...

The map, entitled "Surface Area" on Munroe's site xkcd.com, is a wonderful visualization of the relative sizes of all the major solid bodies in the solar system presented as a familiar world map.

Harvard University researchers described a new, lower size limit for planets to maintain surface liquid water for long periods of time, extending the so-called Habitable or 'Goldilocks'' Zone for ...