The International Astronomical Union defines a planet as a celestial body that orbits the sun, is massive enough that gravity has forced it into a spherical shape, and has cleared away other objects ...

While our Sun prefers to go solo, many other stars are parts of binary systems, with a pair of stars gravitationally bound to each other. In some cases, the stars are far enough apart that planets can ...

NASA’s Double Asteroid Redirection Test, known as DART, did more than shove a small asteroid into a tighter loop around its companion. The September 2022 impact also measurably changed the binary ...

In our solar system, objects are close enough that we can check the orbit and see if has been cleared of other objects. This is problematic if we can only infer rough properties of what could be a ...