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

Mercury is the closest planet to the sun, followed by Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Mercury orbits ...

The formation of our solar system from a singular nebula raises an intriguing question: why did each planet develop with a ...

While the composition of gas and dust in a molecular cloud is fairly uniform, everything changes once a star begins to form.

An object eight times the mass of Jupiter may have swooped around the sun, coming superclose to Mars' present-day orbit ...

For much of January and February, you have the chance to see six planets in our solar system after dark, although two — Uranus and Neptune — will be hard to see without a telescope or high-powered ...

On Feb. 24, from west to east, you can see Mercury, Saturn, Neptune, Venus, Uranus, Jupiter and Mars, all spanning 117.5°, ...

Aside from Earth, no planet in the solar system captures our imagination quite like Mars. The Red Planet is one of the few ...

When astronomers found a large world farther out than Pluto, it became one of the final nails in the coffin of our ninth ...

However, this year a powerful new telescope is coming online that could prove once and for all that there really is a ninth planet in our Solar System. The same year that Pluto was ignominiously ...

She mapped our solar system's "alternate fate" had it housed an extra planet between Mars and Jupiter instead of the existing asteroid belt. They developed a 3D model that simulates how the solar ...