31 May

1996: On 31 May 1996, the NASA/ESA Hubble Space Telescope (Wide Field Planetary Camera 2) made an image which was combined with one taken at the ESO Very Large Telescope (VLT) at the Paranal Observatory in Chile.

Combining this data, a group of European and American astronomers made a major discovery. They identified a huge number of 'young' stellar clusters, in an old elliptical galaxy.

For the first time, it was possible to identify several distinct periods of star formation in a galaxy as old as this one. Elliptical galaxies have always been considered to have undergone one early star-forming period and thereafter to be devoid of star formation. However, the combination of the best and largest telescopes in space and on the ground, allowed astronomers to identify three major groups of stellar clusters. There is an old population of clusters of metal-poor stars, some clusters of old but metal-rich stars and now, seen for the first time, a population of clusters with young and metal-rich stars.

1975: On 31 May 1975, the European Space Agency was officially established.