Hubble Observations of Massive Stars in the Large Magellanic Cloud
This is the Hubble Space Telescope Cosmic Origins Spectrograph (COS) observation of 30 Dor #016 compared with one by the Hubble Space Telescope Imaging Spectrograph (STIS) of the similar star HDE 269810, also in the Large Magellanic Cloud.
The stellar-wind features of helium, carbon, oxygen, and nitrogen are identified by their chemical symbols above; the roman numerals indicate the ionization stages, i.e., the number of electrons removed plus one. ("I" would indicate the neutral atom.) The broad emission components plus blue-shifted absorption are diagnostics of the stellar winds; the absorption forms along the line of sight to the stellar disk, where the wind is approaching us at its full speed. The O V line is a unique feature of the hottest (O2-O3) stars.
The science figure is from C. Evans (Royal Observatory Edinburgh) and his runaway star research team's study, published on May 5, 2010 in the online issue of The Astrophysical Journal Letters.