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

In fact, says Millard, "it's just happenstance that they ... Getty Images The different orbital speeds of the planets in our ...

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

Six planets are parading across the sky, appearing as some of the night's brightest stars. A few easy tips can help you ...

A new study claims it is possible an "alien visitor" could have warped our solar system during its earliest years.

Our Solar System is a carefully balanced celestial dance held together by a virtually perfect balance of gravity and inertia.

Especially since all seven of the other planets in our solar system are about to become visible at once in a great planetary ...

While the planets are technically always "aligned" along the same plane in our sky, seeing so many at once is a special ...

A new study suggests that a planet-sized object may have passed through the solar system billions of years ago.

Worlds will align for a "planetary parade" in January, with four bright and easily visible to the naked eye. But an even ...

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