Binary stars have a vital role in astrophysics.

If their separation and position relative to each other can be measured over a period of time, then their orbit can be calculated. If their distance from us is known (using parallax or some other method) then their masses can be calculated from Kepler’s and Newton’s laws, the only direct way of doing so. It was this kind of data which led to Sir Arthur Eddington’s discovery of the mass-luminosity relationship, one of the most important in astrophysics. Years of patient observation of binary star orbits has yielded the masses of many stars, providing important insights into stellar physics.

The measurement of position and separation is something which amateurs can do very effectively, with a variety of methods. AAQ members are undertaking such observations.