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Last Updated: Friday, 4 June, 2004, 14:42 GMT 15:42 UK
Hubble sees the faintest galaxies
By Dr David Whitehouse
BBC News Online science editor

galaxies, Hubble
Galaxies at the edge of the Universe
The Hubble Space Telescope has analysed the light from some of the most distant galaxies ever seen, and they appear to be similar to those much closer.

Astronomers had thought the first galaxies would have many more hot young stars than older ones.

The telescope has been studying what appear to be red smears in the deepest image of the Universe it has obtained.

The Hubble Ultra Deep Field is the result of a prolonged look over four months at just one small patch of sky.

The space observatory examined in detail just a few of the objects in this picture.

They are points of light 10 times fainter than those which can be analysed by ground-based telescopes.

Studying these galaxies, which existed 400-700 million years after the Big Bang, is important because researchers believe they could be responsible for most of the energy output of the cosmos when it first began to shine.

Odd shapes

The Hubble Ultra Deep Field (HUDF) contains an estimated 10,000 galaxies.

Spiral galaxy viewed in the Hubble Ultra Deep Field, Nasa
Took Hubble 400 orbits to build Ultra Deep Field observation
ACS snapped 800 exposures; each averaged 21 mins long
Total time amounted to 11.3 days of continuous viewing
Most distant light detected at rate of 1 photon per minute
It is centred on the constellation Fornax, next to the constellation Orion. In ground-based images, the patch of sky (just one-tenth the diameter of the full Moon) is largely empty.

Hubble's historic view is actually a combination of two separate images taken by Hubble's Advanced Camera for Surveys (ACS) and its Near Infrared Camera and Multi-object Spectrometer (Nicmos).

Both images reveal galaxies that are too faint to be seen by ground-based observatories, or even in Hubble's previous faraway looks, called the Hubble Deep Fields, taken in 1995 and 1998.

The final ACS image is studded with a wide range of galaxies of various sizes, shapes and colours.

There is also a "zoo" of oddball galaxies littering the field. A few appear to be interacting. Their strange shapes are different from the spiral and elliptical galaxies we see today.

These unusual galaxies chronicle a period when the Universe was more chaotic; order and structure were just beginning to emerge.

The Nicmos sees even farther than the ACS - to the most distant galaxies yet recorded - because the expanding Universe has stretched their light into the near-infrared portion of the electromagnetic spectrum.

Universe graphic, Nasa/Feild

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