VLT Observes the Antennae Galaxies
ALMA gets its first glimpse of cold skies as Thales Alenia Space is providing 25 giant antennas for the most complex and powerful ground-based astronomical observatory ever built. Out of Cape Town, and perched upon a plateau at an altitude of 5,000 meters in the Atacama desert, Northern Chile, the Atacama large Millimeter Array (ALMA) has returned its first images from the skies, showing the Antennae Galaxies (NGC 4038/4039) with unprecedented details in the millimeter and submillimeter wavelengths. Two antennas already delivered by Thales Alenia Space were used to provide these first data. These early observations demonstrate that the new telescope, although only one third complete, is already surpassing all previous similar observatories.
Once fully completed, in 2013, the ALMA will count 66 high-precision antennas, 12 and 7 m in diameters, distributed over 200 pads spread over distances from 15 m to 16 km apart and linked together by fiber optics to function altogether as a single telescope, not a standard radiotelescope array but as a large interferometer.
The ALMA observatory is designed to explore the millimetric and submillimetric parts of the spectrum, located between far infrared and microwaves. Unlike standard radio waves, which are almost unaffected by the atmosphere, millimeteric and submillimetric waves are blocked by water vapor, which is common in the lower atmosphere. That’s why the ALMA has been built in altitude, in one of the driest regions of Earth.
Millimetric and submillimetric astronomy allows observing the coldest parts of the Universe — gas and dust clouds where stars are forming — as well as the most remote and most ancients radiations, from the early times of the Universe, when the first stars lit up and the first galaxies were forming.
ALMA is an international project funded by the European Southern Observatory (ESO), the National Radio Astronomy Observatory (NRAO) in the United States and the National Astronomical Observatory of Japan (NAOJ). The European industrial contribution is provided by a consortium led by Thales Alenia Space, France. The partners include Thales Alenia Space Italy, European Industrial Engineering (Italy) and MT-Mechatronics (Germany). The consortium is providing 25 antennas (with an option for 7 more) each of which weighs more than one hundred tons and required the development of two large 28-wheeled transporters and the building of a road at super highway dimensions for their delivery from the base assembly station to their final location. Due to its high altitude, the ALMA observing site is not permanently manned and operations are conducted from another site, 43 km from the array, at an altitude of only 2,900 m. It’s in this site that the final assembly and acceptance of each single antenna is performed prior to its shipment to the final site at 5,000 m of altitude.