Hubble Ultra Deep Field
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The Hubble Ultra Deep Field (HUDF) is a small region of space imaged by the Hubble Space Telescope from September 24, 2003 through January 16, 2004. The HUDF contains an estimated 10,000 galaxies. The patch of sky in which the galaxies reside (just one-tenth the diameter of the full moon) was chosen because of the low density of bright stars. Although most of the targets visible in the Hubble image can also be seen at infrared wavelengths by ground-based telescopes, Hubble is the only instrument which can make observations of these distant targets at visible wavelengths. Located in the constellation Fornax, the region is below the constellation Orion.
The million-second-long exposure reveals the first galaxies to emerge from the so-called "dark ages," the time shortly after the Big Bang when the first stars reheated the cold, dark universe. The view is actually two separate images taken by Hubble's Advanced Camera for Surveys (ACS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). In total, the image required 800 exposures taken over the course of 400 Hubble orbits around Earth. The total amount of exposure time was 11.3 days. It is the deepest image of the universe ever taken in visible light, looking back in time more than 13 billion years.
Current theories suggest that the Universe has a finite age, and if this was true we might expect very distant (and hence very young) galaxies to look different from the typical older galaxies we see today. This is indeed seen in the HUDF, although some argue that the difference is partly a result of the unusual wavelength used for the HUDF (corresponding to ultraviolet light from the rest-frame of the most distant galaxies).
See also
External links
- Hubble's Deepest View Ever of the Universe Unveils Earliest Galaxies (http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/07/text/) - NASA press release
- NASA site with animations (http://www.nasa.gov/vision/universe/starsgalaxies/hubble_UDF.html)