Arguably HUBBLE’s most important image to date
The Hubble Space Telescope aimed its lens at a very small region of space, about 1/10 of the size of the moon as viewed from Earth, where initially there was nothing to see but darkness. NASA aimed the telescope in an area of apparent darkness in an attempt to look for bright, distant objects. The telescope collected light from this region of the sky for over three months (September 24, 2003 through January 16, 2004). The HUDF was taken in a region of the sky with a low density of bright stars in the near field, allowing for better viewing of dimmer, more distant objects. The Hubble captured and recorded light in the full range from ultra violet to near-infrared spectrum. Looking back approximately 13 billion years the HUDF image shows objects that existed between only 400 million and 800 million years after the big bang. That is, the light from these galaxies were emitted 13 billion years ago, about 8.5 billion years before our Earth had even formed. These photons have been essentially traveling through the universe for the entire history of (space) time. There are approximately 10,000 galaxies in the image. With the exception of four stars (you can see them twinkle), virtually every spec of light visible is an entire galaxy containing anywhere from a thousand (10^3) to a trillion stars (10^12) each. These galaxies are some of the very first to form, indeed able to form in our universe. Interestingly, to observe the entire sky with the same sensitivity, the Hubble would need to observe continuously for a million years.