Does our Solar System have 9 planets or only 8? Astronomers have gone back and forth on that a lot, with Pluto now being classified as a dwarf planet. However, out beyond Neptune there could be ...

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

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 ...

Stargazers will be treated to a rare seven-planet alignment in February. This is what scientists hope to learn.

Take advantage of a special 6-7 planet alignment from Earth's perspective. Planets 'line up' in the skies over California in February.

While most models of solar system formation predict perfectly circular and coplanar orbits for the planets, reality presents a slightly different picture. Successful Simulations: Approximately 1% ...

NASA said the system is thought to be moving at least 1.2 million miler per hour, nearly twice as fast as our solar system.