ALMA: Looking at the birth of the universe

The Atacama Large Millimeter/submillimeter Array (ALMA) is a collection of 66 mobile radio telescopes spread across a large plateau about 16 Km in diameter. By working together, they can detect millimeter and submillimeter wavelengths of light from the coldest and oldest parts of the universe, just tens of degrees above absolute zero. With ALMA, EPFL researchers and scientists across the world are hoping to understand the chemical and physical makeup of so-called molecular clouds, dense interstellar clouds of gas and dust where new stars are born.

Referred to collectively as an astronomical interferometer, ALMA’s 66 high-precision antennas can be moved into different configurations and act as one giant telescope. The antennas’ receivers can pick up electromagnetic waves 0.32 mm – 3.6 mm in length, just above infrared radiation (by comparison, the visible spectrum of light falls between 400 nm – 700 nm in wavelength). These waves form the light signature of some of the earliest and most distant galaxies, objects that generally cannot be observed by standard optics. The ALMA radio telescopes probe incoming waves with the highest possible resolution, and the system uses interferometry techniques to clear up the noise. The analog signals are then converted into digital data and processed by a powerful supercomputer called a correlator, which is essentially ALMA’s “brain”. This is where the data are put together with sophisticated software to produce images that are complemented with other ESO telescope data and can be analyzed by astronomers.

ALMA’s formal life began with its inauguration on March 13, attended by a group of distinguished guests that included Professor Georges Meylan, Director of EPFL’s Laboratory of Astrophysics (LASTRO). EPFL has a long history of involvement with ESO projects, particularly with the Very Large Telescope (VLT) on Cerro Parranal, Chile and the European Extremely Large Telescope (E-ELT) on Cerro Armazones, Chile. EPFL’s research has helped develop the telescope’s adaptive optics system, which allows the real-time correction of signals that are disturbed by Earth’s atmosphere, and has contributed significant knowledge on the system’s mirror cell flexure. The success of EPFL’s collaboration with ESO is reflected by its many doctorate graduates that have gone on to work with the organization.

With ALMA now in full operation, there are already EPFL scientists lined up to carry out their research there, not least Professor Meylan’s group who are heading out to the Atacama desert to study galaxy clusters. “The spectrum of scientific interest for ALMA is enormous”, he says. “It ranges from planets to planet formation, surrounding gas around stars and to the most distant galaxies. It is certain that ALMA is going to provide a lot of observational constraints to understand galaxy, star and planet formation.”

ALMA heralds a whole new era of astronomical exploration, as astronomers can now turn their gazes to the coldest parts of the universe, areas inaccessible with previous radio telescopes. The implications for our understanding of the universe are enormous, as we can extend our view further back in time, when the first galaxies formed. As Professor Meylan excitedly comments: “The 20th century was about star formation and evolution; the 21st century is about galaxy formation and evolution, that is, the fate of the whole universe.”

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About ALMA
ALMA represents almost two decades of global collaboration between Europe, North America, East Asia and the Republic of Chile. As the largest ground-based astronomical project in existence, its billion-dollar cost is jointly funded by the European Southern Observatory (ESO), the US National Science Foundation (NSF), the National Research Council of Canada (NRC), Taiwan’s National Science Council (NSC) and Academia Sinica (AS), and the National Institutes of Natural Sciences (NINS) of Japan. Construction, operations and commissioning are run by the ESO, the US National Radio Astronomy Observatory (NRAO) and the National Astronomical Observatory of Japan (NAOJ), which together form the Joint ALMA Observatory (JAO).