Hubble’s ULLYSES program will observe the ultraviolet light stars emit—and spread that light into its component wavelengths, which are known as spectra. These spectra reflect the intense winds of massive stars in N11 in the Large Magellanic Cloud, set off in teal, and NGC 346 in the Small Magellanic Cloud, set off in purple. By tracing the width of the dips shown on the graph, we can measure the wind speeds. Narrower vertical dips reflect slower winds and wider vertical dips reflect faster winds. The star represented by the purple line is emitting a slower wind, while the star represented by the teal line has intense, faster winds, which means it is losing mass at a faster speed.
