Washington - Using NASA/ESA Hubble Space Telescope, astronomers have assembled a new, improved portrait of our deepest-ever view of the universe, an image that reveals the faintest and most distant galaxies ever seen.
Called the eXtreme Deep Field, or XDF, the photo was assembled by combining ten years of Hubble observations taken of a patch of sky within the original Hubble Ultra Deep Field. The XDF is a small fraction of the angular diameter of the full Moon.
The Hubble Ultra Deep Field is an image of a small area of space in the constellation of Fornax (The Furnace), created using Hubble Space Telescope data from 2003 and 2004. By collecting faint light over one million seconds of observation, the resulting image revealed thousands of galaxies, both nearby and very distant, making it the deepest image of the universe ever taken at that time.
The new full-color XDF image is even more sensitive than the original Hubble Ultra Deep Field image, thanks to the additional observations, and contains about 5500 galaxies, even within its smaller field of view. The faintest galaxies are one ten-billionth the brightness that the unaided human eye can see.
Magnificent spiral galaxies similar in shape to the Milky Way and its neighbor the Andromeda galaxy appear in this image, as do large, fuzzy red galaxies in which the formation of new stars has ceased. These red galaxies are the remnants of dramatic collisions between galaxies and are in their declining years as the stars within them age.
Peppered across the field are tiny, faint, and yet more distant galaxies that are like the seedlings from which today‚Äôs magnificent galaxies grew. The history of galaxies -- from soon after the first galaxies were born to the great galaxies of today, like the Milky Way -- is laid out in this one remarkable image.
Hubble pointed at a tiny patch of southern sky in repeat visits made over the past decade with a total exposure time of two million seconds. More than 2000 images of the same field were taken with Hubble‚Äôs two primary cameras: the Advanced Camera for Surveys and the Wide Field Camera 3, which extends Hubble‚Äôs vision into near-infrared light. These were then combined to form the XDF.
‚ÄúThe XDF is the deepest image of the sky ever obtained and reveals the faintest and most distant galaxies ever seen. XDF allows us to explore further back in time than ever before,‚ÄĚ said Garth Illingworth of the University of California at Santa Cruz, principal investigator of the Hubble Ultra Deep Field 2009 (HUDF09) program.
The Universe is 13.7 billion years old, and the XDF reveals galaxies that span back 13.2 billion years in time. Most of the galaxies in the XDF are seen when they were young, small, and growing, often violently as they collided and merged together.