Heavier than Jupiter, but lighter than a small star, brown dwarfs are difficult to distinguish from giant planets. For years, astronomers have searched for a yardstick that can separate the giant ...

To be a planet, NASA says an object must be big enough that its gravity has cleared away any other objects of a similar size ...

If you’ve seen illustrations or models of the solar system, maybe you noticed that all the planets orbit the Sun in more or less the same plane, traveling in the same direction. But what is above and ...