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

Planet Earth, explained Like Venus and Mars ... in detail—helping us see how other rocky planets behave, even those orbiting distant stars. As a result, scientists are increasingly monitoring ...

Planets with suns like Wolf 359 are subject to huge blasts of radiation that raise questions about their long-term ...

Mars, Venus, Jupiter and Saturn should be visible to the naked eye, but get a telescope and you can spot Neptune and Uranus.