The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

Planet demographics reveal a puzzling lack of worlds in a certain size range throughout the galaxy F or centuries our solar system was the only planetary system known to humans. We had no proof other ...

Feb. 18 marks the 95th anniversary of the discovery of our outermost planet-not-planet. Here's what to know about the short ...

This may explain the strange properties of the orbits of our solar system's planets, which are not quite perfectly circular, and all lie on slightly different planes. NASA artist’s conception of ...

And being so close to the sun, it will be difficult to see. With eight planets in our solar system, they all have some very interesting traits. Here's a quick look at the planets aligning on this ...

New research shows that star activity can distort exoplanet measurements, affecting size, temperature, and atmosphere ...

Temperamental' stars that brighten and dim over a matter of hours or days may be distorting our view of thousands of distant ...