Results from the Hubble Ultra Deep Field
The Hubble Ultra Deep Field image was produced from 400 orbits of the Hubble Space Telescope. The final image was generated from 800 exposures using the Advanced Camera for Surveys (ACS) over a time span from September 24, 2003 to Janaury 16, 2004. The 800 exposures amounted to 11.3 days of observing time.
An examination of the H-UDF image reveals a rich field of about 10,000 galaxies, some of which have an apparent magnitude of around 30th mag. In order to sort out very faint galaxies four color filters were used; blue, green, red, and near-infrared. The entire frame's field of view covers about 1/50th of the entire Moon.
The Ultra Deep Field may reveal some of the first galaxies to emerge from the so-called "dark ages", between 400 to 800 million years (or a redshift range of 7 to 12) after the big bang. The UDF will allow astronomers to study the evolution of galaxy morphologies in the early universe. Does the universe appear to be the same at this very early time as it did when the cosmos was between 1 and 2 billion years old?
In addition to the beautiful classical spiral galaxies seen in the image, there are many odd shaped galaxies that do not appear to have a coherent structure. Some of them appear to be interacting and some appear to look like chains. The non-coherent structures chronicle a period when the universe very young and chaotic, when order and structure were just beginning to emergy.
In order to detect the farthest galaxies ever observed, the Hubble Space Telescope's NICMOS (NIR) camera was used to record an image of the same field. Since the expansion of the spacetime metric "stretches" the light from faint galaxies into the infrared portion of the spectrum, the near-infrared image shows some of the earliest, most distant galaxies ever observed. Galaxies at a redshift of about 12 (or only 400 million years after the big bang) may be present in the NICMOS UDF image. Followup spectroscopy of selected candidate sources using large ground based telescopes (such as the Keck) will help confirm their redshifts. In addition to detecting distant galaxies, the NICMOS image will also be helpful in finding intrinsically red objects, such as elliptical galaxies and galaxies that have red colors due to a high degree of dust absorption.
The Hubble Ultra Deep Field will be the deepest ever view of the cosmos until the launch of the James Webb Space Telescope in 2011.