'The Hubble Ultra Deep Field is an image of a small area of space in the constellation Fornax, created using Hubble Space Telescope data from 2003 and 2004. By collecting faint light over many hours of observation, it 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 (2012) reaches much fainter galaxies, and includes very deep exposures in red light from Hubble's new infrared camera, enabling new studies of the earliest galaxies in the universe. The XDF contains about 5,500 galaxies even within its smaller field of view. The faintest galaxies are one ten-billionth the brightness of what the human eye can see.'
Credit: HUBBLESITE
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An interesting point is that the colour of objects moving away is shifted towards the red, whilst objects moving towards the observer are bluer. However, larger galaxies with older stars are intrinsically redder than galaxies bulk-forming new stars. Though intelligent guesses can be made from the size and shape of galaxies, the only way to reliably separate the two reddening effect is through a spectral investigation. The spectral lines are not available to us here, and it is unclear if data from the IR and UV portions of the spectra have been recoloured (i.e. shifted into the visible) as the composite image is built up. For this reason, there is limited investigation possible to establish the size and distance of the many galaxies visible in the image.
Nevertheless, we can do some very basic colour investigation as illustrated above right. You might like to try some more complex processing yourself. Click to select the area to investigate.
The pixelation of the digital image is apparent. A photographic plate has greater information density, and you would need to conduct your investigation with a microscope rather than a telescope, but the level of information superposition achieved above is not possible by analogue methods.