It is trivial to obtain the size of objects, so long as you have some information about a satellite orbiting it. It's how we get the mass of many interstellar

It is trivial to obtain the size of objects, so long as you have some information about a satellite orbiting it. It's how we get the mass of many interstellar objects, and it's how we know that dark matter exists. http://astro.physics.uiowa.edu/ITU/glossary/keplers-third-law/ http://astro.physics.uiowa.edu/ITU/glossary/keplers-third-la...