The International Astronomical Union defines a planet as a celestial body that orbits the sun, is massive enough that gravity has forced it into a spherical shape, and has cleared away other objects ...

Earth’s orbit around the Sun is not circular, but an ellipse that is slightly elongated with an eccentricity of 0.017. (An eccentricity of 0 is a circle, while the dwarf planet Pluto has a relatively ...

NORFOLK, Va. — Each planet in our solar system takes a different amount of time to complete one orbit around the sun. For example, Mercury, being closest to the sun, takes just 88 Earth days to ...

This image from a simulation of atmospheric flow shows temperature patterns on one of the newly discovered planets (61Virb), which is hot enough that it glows with its own thermal emission. A movie of ...