Sights set on galactic birth

September 15, 2000

Astronomers have produced the deepest ground-based image of the sky, allowing them to probe galactic birth at an unprecedented scale.

The team from the University of Durham used the Anglo-Dutch William Herschel Telescope, which is sited at La Palma, to survey objects dating from when the universe was a tenth of its current age.

Although the Hubble Space Telescope captured similar images almost five years ago, the William Herschel Deep Field covers more than ten times the area. This allows scientists to locate the few far distant galaxies that are bright enough for the spectra of their light to be analysed.

Nigel Metcalfe, who led the project, said: "If you want to look back to when galaxies were created, you cannot use normal spectroscopy techniques because the objects are too faint. The only way to do it is to look at their colours."

The astronomers pointed the 4.2m William Herschel Telescope at the same patch of the night sky for up to 40 hours. This was repeated to gather light from the galaxies at different wavelengths: ultraviolet, blue, red and infrared.

The images were combined to produce vivid, colour pictures of the outer limits of the visible universe.

Ten of these galaxies have been picked as being especially distant, judging from the colour of their light, with red shifts between five and seven, while also being bright enough to be studied in detail by an 8m telescope such as Gemini.

The scale of the William Herschel Deep Field will help scientists discover how structure formed in the early universe.

The research will be published in the Monthly Notices of the Royal Astronomical Society.

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