ASTRONOMY: Very Large Telescope expands

The very Large Telescope (vLT) at Cerro Paranal, Chile, is moving closer to full operation, with the third of four unit telescopes (back right) achieving first light in January. Polishing of the mirror for the European Southern Observatory's fourth and final unit telescope (foreground) was completed in December, and that mirror is scheduled to be delivered to Chile by April.

When all four telescopes are in operation, they will be able to observe individually or to be combined to work as one for interferometry. Together they have 12 foci, instruments for observing wavelengths from 300 nm to 25 µm, and a variety of spectroscopic modes that will allow astronomers to look at objects ranging from single stars to star-forming regions to clusters of galaxies. The vLT is also equipped with an active optics system to cancel out atmospheric disturbances.

Each telescope has been given a name in the language of Chile's indigenous Mapuche people (l to r): Antu, the Sun; Kueyen, the Moon; Melipal, the Southern Cross; and Yepun, Sirius (foreground). Instruments attached to Antu will eventually include the Infrared Spectrometer and Array Camera (ISAAC) and the High-Resolution IR Echelle Spectrometer (CRIRES), both for 1 to 5 µm, and the Focal Reducer Low-Dispersion Spectrograph (FORS 1) for 0.3 to 1 µm. Kueyen will have FORS 2, the Uv-visual Echelle Spectrograph (UvES) for 0.3 to 1 µm, and the Fibre Large Area Multi-Element Spectrograph (FLAMES) for 0.37 to 1 µm. Melipal will consist of the visible Multi-Object Spectrograph (vIMOS) for 0.37 to 1 µm, the Nasmyth Adaptive Optics System (NAOS) for 1 to 5 µm, and Single Far Object Near IR Investigation (SINFONI) for 1 to 2.5 µm.

Yepun will be equipped with the Near Infrared Multi-Object Spectrograph (NIRMOS) for 1 to 1.7 µm and the vLT Mid Infrared Imager Spectrometer (vISIR) for the 8 to 25 µm region. The telescope's Nasmyth focus will be reserved for instruments brought in by outside astronomers. When the telescopes are combined into the vLT Interferometer (in the low building between the first and fourth telescopes), they will be used with the Astronomical Multi-Beam Recombiner (AMBER), a near-infrared and red imaging and spectrographic instrument; the Mid Infrared (MIDI) instrument for 8 to 13 and 17 to 26 µm; and the Instrument for Phase-Referenced Imaging and Microarcsecond Astrometry (PRIMA) for observing particularly faint objects.

FORS#1, FORS#2, ISAAC, and UvES are in use and have already returned a number of high-quality images. All the instruments are scheduled to be installed by 2003.