Imagine you observe a 1M white dwarf orbiting an unseen object with P = 0.02 years and a a = 0.2AU. What is the unseen object? Why? (your explanation should include a calculation)
How can astronomers determine the difference between “hydrostatic equilibruim” and “just happens to be spherical”?
This is relevant for the definition of a dwarf planet. I presume the answer will be, well, if we can tell the mass of the body and guess the material. I don't find this very satisfactory because ...