Adding New Colours to Interferometry: AMBER joins the VLT Interferometer(Forwarded)

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For immediate release: 5 April 2004

ESO Press Release 07/04

Adding New Colours to Interferometry

AMBER joins the VLT Interferometer [1]

Another vital step has been accomplished as planned towards full operation of
the ESO Very Large Telescope Interferometer (VLTI) at the Paranal Observatory in
Chile, one of the world's foremost astronomical facilities.

In the night of March 20-21, 2004, a team of astronomers and engineers from
France, Italy, Germany and ESO celebrated the successful assembly and completion
of the first on-line tests of the latest of the first-generation VLTI
instruments, the Astronomical Multiple BEam Recombiner (AMBER). They combined
the two beams of light from the southern star Theta Centauri from two test
telescopes ("siderostats" with 40-cm aperture, cf. ESO PR 06/01) to produce
strong and clear interferometric fringes. Equally successful observations were
then obtained on the bright star Sirius, and consistently repeated during the
following nights.

A joint project

This is the most promising result of about 7 years of dedicated work by a team
of over 40 astronomers and engineers. The AMBER instrument has been developed by
a European consortium of seven research institutes in three ESO member
countries, the main partners being: Laboratoire d'Astrophysique de Grenoble
(LAOG), Laboratoire Universitaire d'Astrophysique de Nice (LUAN) and
Observatoire de la Côte d'Azur in France, Max-Planck-Institut für
Radioastronomie (MPIfR) in Bonn, Germany, and Osservatorio Astrofisico di
Arcetri (OAA; part of INAF, the Italian National Institute for Astrophysics) in
Florence, Italy.

The total cost of AMBER is of the order of 5.9 million Euros, mostly contributed
by the members of the consortium. It was built through an agreement with ESO,
which rewards the consortium solely with guaranteed observing time. According to
the contract, the consortium will receive 60 observing nights to be spread among
two or three of the four 8.2-m VLT Unit Telescopes and 130 nights with the four
Auxiliary Telescopes over a period of eight years.

AMBER: soon to join three light beams at once

ESO PR Photo 09a/04
AMBER at the VLT Interferometric Laboratory

Caption: ESO PR Photo 09a/04 shows the AMBER instrument in the VLT
Interferometric Laboratory at Paranal.

The AMBER instrument is mounted on a 4.2 x 1.5 m precision optical table, placed
in the VLT Interferometric Laboratory at the top of the Paranal mountain, cf. PR
Photo 09/04. The total shipping weight of the instrument and its extensive
associated electronics was almost 4 tons.

AMBER is the latest addition to the VLTI and completes the planned set of
first-generation instruments for this facility. It continues the success story
of the interferometric mode of the VLT, following the unique initial scientific
results obtained by the VINCI and MIDI instruments, the installation of the
first MACAO adaptive optics systems and the recent arrival of the first 1.8-m
Auxiliary Telescope at Paranal (ESO PR 01/04).

The interferometric technique can achieve images, as sharp as those of a
telescope with a diameter equivalent to the distance between the telescopes in
the interferometer. For the VLTI, this distance can be as large as 205 meters,
resulting in a resolution of 0.001 arcsec in the near-infrared spectral region
(at 1 um wavelength). The latter measure corresponds to about 2 metres on the
surface of the Moon.

AMBER is a very powerful complement to the other instruments already installed
at the VLTI and offered to the astronomical community. AMBER is indeed sensitive
in the near-infrared wavelength region of 1 to 2.5 microns while the present
instrument, MIDI, covers the 8 to 13 microns range. Moreover, AMBER will be able
to perform spectroscopic measurements with a spectral resolution up to 10,000.

ESO PR Photo 09b/04
The AMBER instrument (detail)

Caption: ESO PR Photo 09b/04 shows in the foreground some of the
mirrors and optical fibers (yellow cables), as well as the dichroic
mirrors by means of which the light beams from the three telescopes
are split into separate wavebands.

AMBER will also combine three light beams from as many telescopes -- this is a
world premiere for large telescopes such as the VLT. The ability to combine
three beams, rather than just two as in a conventional interferometer, provides
a substantial increase in the efficiency of observations, permitting astronomers
to obtain simultaneously three baselines instead of one. The combination of
these three baselines also permits the computation of the so-called closure
phase, an important mathematical quantity that can be used in imaging applications.

Exciting scientific opportunites

These observational capabilities, characterized by the highest possible image
sharpness and enormous sensitivity, make AMBER a unique instrument for
addressing a large number of frontline astronomical topics. In particular, it is
expected that AMBER will greatly contribute by:

* Obtaining very detailed images of dusty discs around young stars for studies
of the formation of stars and of planets in other solar systems. With its
exceedingly sharp view, AMBER will be able to observe structures of the size of
Mercury's orbit in stars located in the major nearby star-forming regions.

* Providing new images and spectra that will improve our understanding of the
physics of black holes believed to be present in the central parts of all
galaxies. AMBER will make it possible to look at the innermost parts of other
galaxies, thereby providing information on their central engines.

* Detecting for the first time the light of "hot Jupiters", that is planets
orbiting very close to their parent stars. It will be possible to determine the
mass of these planets and to study their atmosphere directly by means of
spectral observations. This is equivalent to detecting -- and analysing -- the
light of a dragonfly in the vicinity of a lighthouse.

Next Steps

After the first very successful tests, AMBER is now entering a long phase of
observational tests that will serve to adjust its many parts and to optimize its
performance. They include tests at the end of May to be made by combining the
light beams from two, then three of the 8.2-m VLT Unit Telescopes. In 2005, the
instrument will be offered to the astronomical community who will then be able
to use it, either with the Unit Telescopes or with their little brothers, the
1.8-m moveable Auxiliary Telescopes.

Notes

[1] This ESO press release is coordinated and issued simultaneously with
releases in the respective languages by the Centre National de la Recherche
Scientifique in France (CNRS Press Release), the Max-Planck Institut für
Radioastronomie in Germany (MPI Press Release) and Osservatorio Astrofisico di
Arcetri in Italy (INAF Press Release).

[2] The institutes taking part in the AMBER consortium are :

* LAOG - Laboratoire d'Astrophysique de Grenoble, France
* LUAN - Laboratoire d'Astrophysique Universitaire de Nice, France
* MPIfR - Max-Planck Institut für Radioastronomie, Bonn, Germany
* OAA - Osservatorio Astrofisico di Arcetri (part of INAF, the Italian
National Institute for Astrophysics), Florence, Italy
* OCA - Observatoire de la Côte d'Azur, France

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