Saturn has dozens of new moons, bringing it to a total of 274. All of the new moons are between 2 and 4 kilometres wide, but at what point is a rock too small to be a moon?

SPHEREx, NASA’s latest astrophysics observatory, has launched aboard a Falcon 9 rocket alongside PUNCH, a mission studying solar wind. SPHEREx will create a 3D map of the universe, helping to uncover ...