""By taking very long exposure pictures of regions of the sky with the Hubble Space Telescope, astronomers have created so-called ‘deep fields’ that have revealed much about the early Universe.
The first deep field, the Hubble Deep Field North, was observed over ten consecutive days during Christmas 1995.
The resulting image consisted of 342 separate exposures, with a total exposure time of more than 100 hours, compared with typical Hubble exposures of a few hours.
The observed region of sky in Ursa Major was carefully selected to be as empty as possible so that Hubble would look far beyond the stars of our own Milky Way and out past nearby galaxies.
The results were astonishing – almost 3,000 galaxies were seen in the image.
In 1996 it was decided to observe a second deep field, the Hubble Deep Field South, to assess whether the Hubble Deep Field North was indeed a special area and thus not representative of the Universe as a whole. This time the field also contained a quasar, which was used as a cosmological lighthouse and provided valuable information about the matter between the quasar and the Earth.
These images gave astronomers a peephole to the ancient Universe for the first time, and caused a real revolution in modern astronomy.
But they did not hold all the answers — to find out more about the galaxies in the images, astronomers had to carefully look at each one with other instruments, a difficult and time-consuming job.
Now, for the first time, VLT’s MUSE instrument can do both jobs at once.""
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