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AAO Press Releases

20 October 1997

Anglo-Australian Observatory telescopes help point Hubble Space Telescope

The two Anglo-Australian Observatory telescopes, the Anglo-Australian Telescope (AAT) and the UK Schmidt Telescope (UKST) were used recently to pinpoint the area which will be intensively studied next year with the Hubble Space Telescope (HST).

Over the Christmas and New Year of 1995/96, the Hubble Space Telescope spent hundreds of hours examining a small patch of northern sky. The Hubble Deep Field (HDF), as it became known, provided the 'deepest' ever image of the Universe, and provides astronomers with valuable information about the formation of galaxies out to distances of 10 billion light years.

In 1998, the HST will again spend hundreds of hours looking at a small patch of sky but this time in the south. The UKST and the AAT played key roles in finding a suitable area, referred to as the Hubble Deep South (HDF-S).

This time it will contain a distant quasar at the centre of the field. (A quasar is a galaxy with a very bright centre, thought to be caused by the destruction of stars and gas falling into a black hole at the centre of the galaxy.) The quasar will be used to light-up material lying between the Earth and quasar, yielding new information on otherwise invisible material lying many thousands of millions of light years from the Earth. This material may be associated with the formation of star systems such as our own galaxy, and may reveal some the early history of the Universe.

Finding a suitable patch of sky was not easy. Areas to look at are very limited, due to the constraints of the HST orbit and the need to avoid pointing at the sun and the earth. Other limitations include avoiding bright stars and not being obscured by our own galaxy. In fact, there are only about a dozen suitable patches.

A patch of sky in the constellation Tucana containing a likely quasar was identified by analysing a photographic plate taken ten years ago with the UKST. The quasar was confirmed with the 2-degree field instrument on the AAT. The quasar is over 10 thousand million light years from Earth its relatively bright optical magnitude has led to it being the choice for the HDF-S.

The identification of the area as the HDF-S demonstrates the power of UK Schmidt Telescope archival material, and the significance of the follow-up work done by the Anglo-Australian Telescope and the 2 degree field facility. It also emphasises the important role that ground-based telescopes play in relation to the HST.

To see an image of the field click here.

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Roger Bell
01 Jan 1998