Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. BY Draconis is a multi-star system in the constellation Draco. It consists of at least three components. Components A and B form a close binary star system with a short orbital period of only 5.98 days. These may be pre-main sequence objects that are still in the process of collapsing. Their individual spectroscopic classifications are dK5e and dK7e. They form the prototype of a class of variable stars known as BY Draconis variables.