How do astronomers work out the orbital period for newly discovered cestial bodies?
We have centuries’-worth of research into the mechanics of planetary motion in the solar system and the laws that govern them, thanks to the people like Johannes Kepler and Isaac Newton. All you need in order to calculate an object’s orbital period is its semi-major axis. For solar system objects, the semi-major axis is related to the period of the orbit by Kepler’s third law. In turn, the semi-major axis of a body can be calculated from its orbital state vectors (vectors of position and velocity). There have been several hundred observations of Makemake since its discovery, providing plenty of data to perform such calculations. What’s more, the recently discovered celestial objects can sometimes be found on much older photographs, where they have previously gone unnoticed or taken for some other object. These “precovery” observations allow for even more accurate calculations. Makemake has been found on photos dating from 1950s.
