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 ...

This video explores the key characteristics of each planet within our solar system. Suitable for teaching science at KS1 and ...

Earth, our home planet, is a world unlike any other. The third planet from the sun, Earth is the only place in the known ...

At the right point of the orbit and stellar cycle, the star’s chromosphere brightens.

Astronomers using NASA’s Hubble Space Telescope have measured the rotation rate of an extreme exoplanet by observing the varied brightness in its atmosphere. This is the first measurement of the ...

In the cold, dark outskirts of planetary systems far beyond the reach of the known planets, mysterious gas giants and planetary masses silently orbit their stars—sometimes thousands of astronomical ...

A sunlike star next door called Alpha Centauri A may host a huge planet, researchers report in two studies in press in Astrophysical Journal Letters. The planet candidate orbits in its star’s ...

A Jupiter-size exoplanet orbiting a dead star baffled astronomers. But the planet named WD 1856 b could preview the fate of our own solar system when the sun dies.

Planetary scientists are proposing a new definition of a planet to replace one that many researchers view as sun-centric and outdated. The current definition—established in 2006 by the International ...