The Hubble Space Telescope, which orbits 559 kilometers (357mi) above the surface of Earth, has captured the farthest, deepest, and oldest view of the of the observable universe. In the image above there are around 5,500 visible galaxies, with some of them being billions of light years away and 13.2 billion years old — just 450 million years after the Big Bang and the creation of the universe.
The image, officially dubbed the Extreme Deep Field (XDF), is constructed out of 2,000 images of the southern sky (constellation Fornax), captured over a decade. The individual images were captured by both the Advanced Camera for Surveys (2x 8-megapixel CCD), and the newer Wide Field Camera 3 (2x 8MP CCD, plus an extra 1MP CCD tuned specifically to infrared light). The total exposure time, in case you’re an astronomer or night sky photographer, is 2 million seconds.
Taking a closer look at the XDF (see a larger version), there are lots of spiral galaxies (similar to our own Milky Way), red galaxies (the remnants of galaxy collisions, which were much more common when the universe had first formed), and tiny dots that are mere galaxy seedlings. Remember, the XDF peers 13.2 billion years into the past, to when the universe was just 450 million years old. Today, 13.2 billion years later, the galaxies will look completely different — they will have moved apart, some will have ceased to exist, and the seedlings might have grown into full-blown galaxies.
So you have some idea of the scale of this picture, NASA has produced a fantastic illustration that shows you just how focused the Hubble XDF is. If you were on the ground looking up, the Moon in the image below would be about half the width of your finger held at arm’s length. In other words, XDF is no bigger than, say, the period at the end of this sentence, viewed at arm’s length. In the XDF image, the faintest galaxies are one ten-billionth of the brightness that your eyes can actually perceive.
Here’s an even better demonstration that will probably blow your mind. Look up at the night sky and find a single star — and then imagine that behind that star there are roughly 5,000 galaxies that are too far away to be seen by the naked eye. Then remember that an average-sized galaxy contains 500 billion stars…