The European Space Agency (ESA) is Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
Find out more about space activities in our 23 Member States, and understand how ESA works together with their national agencies, institutions and organisations.
Exploring our Solar System and unlocking the secrets of the Universe
Go to topicProtecting life and infrastructure on Earth and in orbit
Go to topicUsing space to benefit citizens and meet future challenges on Earth
Go to topicMaking space accessible and developing the technologies for the future
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This image, taken with Hubble's Advanced Camera for Surveys, shows the core of 47 Tucanae. Multiple photos of this region allowed astronomers to track the 'beehive swarm' motion of stars. Precise velocities were obtained for nearly 15 000 stars in this cluster.
The image was taken during a seven year study performed by Hubble, which provided astronomers with the best observational evidence yet that globular clusters sort out stars according to their mass, governed by a gravitational billiard ball game between stars. Heavier stars slow down and sink to the cluster’s core, while lighter stars pick up speed and move across the cluster to its periphery. This process, called 'mass segregation', has long been suspected for globular star clusters, but has never before been directly seen in action.