Our definition of a planet has changed over the years — causing a bit of confusion. | Credit: wasan prunglampoo/Getty Images Over the past 250 years, the number of "planets" in our solar system has ...

The official number of exoplanets—planets outside our solar system—tracked by NASA has reached 6,000. Confirmed planets are added to the count on a rolling basis by scientists from around the world, ...

Astronomers are investigating a strange class of exoplanets known as eccentric warm Jupiters — massive gas giants that orbit their stars in unexpected, elongated paths. Unlike their close-orbiting ...

The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper’s authors have dubbed ...

An exoplanetary system about 116 light-years from Earth could flip the script on how planets form, according to researchers who discovered it using telescopes from NASA and the European Space Agency, ...

Over the past 250 years, the number of "planets" in our solar system has ranged from six to nine — and, briefly, even 11 — depending on what astronomers knew at the time and how they defined a planet.