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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Artist’s impression of quasars, the cores of galaxies where an active supermassive black hole is pulling in matter from its surroundings at very intense rates, located at increasingly larger distances from us.
As material falls onto the black hole, it forms a swirling disc that radiates in visible and ultraviolet light; this light, in turn, heats up nearby electrons, generating X-rays. The relation between the ultraviolet and X-ray brightness of quasars can be used to estimate the distance to these sources – something that is notoriously tricky in astronomy – and, ultimately, to probe the expansion history of the Universe.
A team of astronomers has applied this method to a large sample of quasars observed by ESA’s XMM-Newton to investigate the history of our cosmos up to 12 billion years ago, finding there might be more to the early expansion of the Universe than predicted by the standard model of cosmology.