First Light for ESO VLT's Auxiliary Telescope No.4 (Forwarded)

ESO Education and Public Relations Dept.

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For Immediate Release: 22 December 2006

ESO Press Photo 51/06

Little Brother Joins the Large Family

First Light for VLT's Auxiliary Telescope No.4

On the night of 15 December 2006, the fourth and last-to-be-installed VLTI
Auxiliary Telescope (AT4) obtained its 'First Light'. The first images
demonstrate that AT4 will be able to deliver the excellent image quality
already delivered by the first three ATs. It will soon join its siblings
to perform routinely interferometric measurements.

The VLT is composed of four 8.2-m Unit Telescope (Antu, Kueyen, Melipal
and Yepun). They have been progressively put into service together with a
vast suite of the most advanced astronomical instruments and are operated
every night in the year.

Contrary to other large astronomical telescopes, the VLT was designed from
the beginning with the use of interferometry as a major goal. The VLT
Interferometer (VLTI) combines starlight captured by two or three 8.2- VLT
Unit Telescopes, dramatically increasing the spatial resolution and
showing fine details of a large variety of celestial objects.

However, most of the time the large telescopes are used for other research
purposes. They are therefore only available for interferometric
observations during a limited number of nights every year. Thus, in order
to exploit the VLTI each night and to achieve the full potential of this
unique setup, some other (smaller), dedicated telescopes were included
into the overall VLT concept.

These telescopes, known as the VLTI Auxiliary Telescopes (ATs), are
mounted on tracks and can be placed at precisely defined "parking"
observing positions on the observatory platform. From these positions,
their light beams are fed into the same common focal point via a complex
system of reflecting mirrors mounted in an underground system of tunnels.

The Auxiliary Telescopes are real technological jewels. They are placed in
ultra-compact enclosures, complete with all necessary electronics, an air
conditioning system and cooling liquid for thermal control, compressed air
for enclosure seals, a hydraulic plant for opening the dome shells, etc.
Each AT is also fitted with a transporter that lifts the telescope and
relocates it from one station to another. It moves around with its own
housing on the top of Paranal, almost like a snail.

The VLTI is arguably the world's most advanced optical device of this
type. It has already demonstrated its powerful capabilities by addressing
several key scientific issues, such as determining the size and the shape
of a variety of stars (ESO PR 22/02, PR 14/03, PR 31/03, and PR 09/06),
measuring distances to stars (ESO PR 25/04), probing the innermost regions
of the proto-planetary discs around young stars (ESO PR 27/04 and PR
35/06) or making the first detection by infrared interferometry of an
extragalactic object (ESO PR 17/03).

National contacts for the media:

Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Finland: Ms. Riitta Tirronen, +358 9 7748 8369
Denmark: Dr. Michael Linden-Vørnle, +45-33-18 19 97
France: Dr. Daniel Kunth, +33-1-44 32 80 85
Germany: Dr. Jakob Staude, +49-6221-528229
Italy: Dr. Leopoldo Benacchio, +39-347-230 26 51
The Netherlands: Ms. Marieke Baan, +31-20-525 74 80
Portugal: Prof. Teresa Lago, +351-22-089 833
Sweden: Dr. Jesper Sollerman, +46-8-55 37 85 54
Switzerland: Dr. Martin Steinacher, +41-31-324 23 82
United Kingdom: Mr. Peter Barratt, +44-1793-44 20 25

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