Hubble eXtreme Deep Field Image Reveals Early Universe

April Flowers for redOrbit.com – Your Universe Online

Researchers using the Hubble Telescope have assembled a new and improved portrait of our deepest-ever view of the Universe. The eXtreme Deep Field (XDF) photo was compiled by combining ten years worth of NASA and ESA Hubble Space Telescope observations taken of a patch of sky within the original Hubble Ultra Deep Field.

The Hubble Ultra Deep Field is a small area of space in the Fornax (The Furnace) constellation created using Hubble data from 2003 and 2004. The researchers collected over one million seconds of observation, revealing thousands of galaxies, both nearby and very distant. The resulting image was the deepest of the Universe ever taken at that time.

Because of additional observations, the new full color XDF image is even more sensitive than the Ultra Deep Field image. XDF contains about 5500 galaxies, even though its field of view is smaller than the Ultra Deep Field. The faintest galaxies visible in the XDF are about one ten-billionth the brightness that can be seen with the naked human eye.

Different types of galaxies are visible in the XDF, from magnificent spiral galaxies shaped much like the Milky Way to fuzzy red galaxies, which are the remnants of dramatic collisions between galaxies and are on their way to dissolution. Scattered across the field are tiny, faint, distant galaxies that are like seedlings from which the large galaxies grew. The history of galaxies, stretching from the first faint galaxies to be born to the great galaxies of today is laid out in this one image.

The total exposure time, taken in repeat visits to the same tiny patch of southern sky over the last ten years, is 2 million seconds. Over 2000 images of the same field of view were taken with Hubble’s two primary cameras: the Advanced Camera for Surveys and the Wide Field Camera 3, which extends Hubble’s vision into near-infrared light. These were then combined to form the XDF.

“The 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,” said Garth Illingworth of the University of California at Santa Cruz, principal investigator of the Hubble Ultra Deep Field 2009 (HUDF09) program.

Current estimates put the age of the Universe at about 13.7 billion years old, and the XDF reveals galaxies that span back 13.2 billion years. Most of the galaxies captured in the XDF are seen when they were young, small and growing. This growth was often violent as they collided and merged together. The early Universe saw the dramatic birth of galaxies containing brilliant blue stars much brighter than our own Sun, and the light from these events is just arriving at Earth now. The XDF thus becomes a time tunnel into the distant past of the Universe. The youngest galaxy found in the XDF existed just 450 million years after the Big Bang.

Hubble’s launch in 1990 allowed astronomers to see half way back to the Big Bang, about seven billion years back, providing compelling visual evidence that the Universe is changing as it ages. The XDF allows astronomers to watch the emergence of structure in the nascent Universe and the subsequent dynamic evolution of galaxies.

Scheduled to launch in 2018, the James Webb Space Telescope, which will be a collaborative effort between NASA and the ESA, will be aimed at the XDF to study it with infrared vision. The infrared is expected to allow the Webb Telescope to see galaxies that exited when the Universe was just a few million years old.

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