Moons circle planets, and planets circle stars. Now, astronomers have learned that planets may also circle celestial bodies almost as small as planets. NASA’s Spitzer Space Telescope has spotted a ...

It is often remarked upon that the distribution of rings and moons around the giant planets of the Solar System – Jupiter, Saturn, Uranus, and Neptune – are themselves like miniature solar systems.

Astronomers have found six new worlds that look like planets, but formed like stars. These so-called rogue worlds are between five and 15 times the mass of Jupiter, and one of them may even host the ...