Star Formation in R136: A Cluster of O3 Stars Revealed by Hubble Space Telescope Spectroscopy

The R136 cluster in 30 Doradus is the prototype “super star cluster,” and the only example sufficiently close that its massive star content can be studied directly. We have used the Hubble Space Telescope to obtain spectra of 65 of the bluest, most luminous stars in R136 and find that the majority of these stars are of type O3, the hottest, most luminous, and most massive stars known.