A 6th-magnitude spectroscopic binary star in Monoceros named after J. S. Plaskett, who discovered in 1922 that it was the most massive binary known; it is also known as V640 Mon. According to current measurements, the individual stars are both O-type giants or supergiants of around 54 and 56 solar masses. Their orbital period is 14.4 days. Plaskett’s Star lies about 5000 l.y. away.