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 Hubble Space Telescope image shows Sirius A, the brightest star in our nighttime sky, along with its faint, tiny stellar companion, Sirius B.
Astronomers overexposed the image of Sirius A (centre) so that the dim Sirius B (tiny dot at lower left) could be seen. The cross-shaped diffraction spikes and concentric rings around Sirius A, and the small ring around Sirius B, are artifacts produced within the telescope's imaging system. The two stars revolve around each other every 50 years. Sirius A, only 8.6 light-years from Earth, is the fifth closest star system known.
This image was taken 15 October 2003, with Hubble's Wide Field Planetary Camera 2. Based on detailed measurements of the position of Sirius B in this image, astronomers were then able to point the STIS instrument exactly on the white dwarf and make the measurements to determine its gravitational redshift and mass.