In the summer of 1996, the European Space Agency announced that it would be suspending the operations of the International Ultraviolet Explorer. Astronomers who were most unhappy about that announcements were likely to be studying what types of objects?

Very hot Stars

Explanation:

Astronomers that were most unhappy about the decision of the European space agency to suspend operations of intentional ultraviolet explorer in summer of 1996 were those studying very hot stars. The international ultraviolet explorer was designed to to take ultraviolet spectra. The ultraviolet explorer was used in detecting very hot stars. With the shut down of the international ultraviolet explorer, the astronomers studying the very hot stars were affected and thus very unhappy about the announcement in 1996.