Plaskett’s 1922 discovery

John Stanley Plaskett’s early research involved binary stars. These are two stars that revolve around each other. In 1921 and 1922 he made made many obervations of a fairly bright star in the constellation Monoceros . This (binary) star turned out to be  the most massive binary known. According to current measurements, the individual stars are both blue supergiants of 51 and 43 times the mass of the Sun. The star is now named Plaskett’s star and  lies about 5000 light years. away.