Albedo is a term for how much light is reflected off of an object.  It is usually measured as a percentage where 100% reflects all the electromagnetic radiation that hits it and 0% reflects none.  Measuring albedo can tell us a lot about an object in space, such as how much ice is on the surface or what kinds of metals it contains.  The mysterious change of a dwarf planet’s albedo became a major plot point in Ender’s Game.

In the course of my research, I stumble upon interesting words that I think science fiction writers should know about.  While writing the three posts on Basic Navigation, I learned two terms used to describe the position of a planet in orbit of a star.  Perihelion is the point where a planet is as close to its star as it can get; Aphelion is when it is furthest away.