In 2003, astronomers decided to point the Hubble Space Telescope (HST) at a dark patch of sky where there were apparently no stars or galaxies, just out of curiosity. What they saw after combining the data from all the exposures (totalling up to 11 days) totally changed the way we looked at our place in the Universe. Where once thought to be empty space, the image, now known as the Hubble Ultra Deep Field, was filled with thousands of distant galaxies. Barring a few stars in our own Galaxy, every other single patch or blob in the image represented another galaxy – each with its own collection of hundreds of billions of stars and clouds of interstellar gas. Some of these galaxies were estimated to be about 13 billion light years away, which meant that these galaxies were being observed as they appeared 13 billion years ago! What could be more awe-inspiring than that? The Hubble Ultra Deep Field remains as one of my all-time favourites in astronomical imagery.
In 2009, scientists decided to try it again, this time with new cameras installed on the Hubble Space Telescope during a final servicing mission by astronauts recently (it will be replaced by the James Webb Telescope soon). This time, the telescope managed to capture light from much deeper in space – to reveal infant galaxies just 600 million years after the Big Bang (about 13.1 billion years ago). This image has only been recently released by NASA/ESA: