Milky Way Crossing the Sky of ALMA


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Above the last antenna in the left center horizon, the bright object visible is not a star itself, but the great globular cluster Omega Centauri. Next to it, in the beginning of Milky Way arc, are spotted the bright stars of Alpha and Beta Centauri. Along his path we can enjoy the magnificent presence of our Galaxy full of gas and dust, star clusters and emission nebulae, as well as the orange star Antares from Scorpius constellation, and the dark streaks that are part of Rho Ophiuchi cloud complex, which connects this region to the main arm of Milky Way. Below right, we find planet Saturn and a faint white light called the Zodiacal Light, coming up as a backlight behind the antenna of ALMA (DV-21) with12 meters in diameter, is capturing the wavelengths from vast cold clouds in the interstellar space. This are the first tests to experiment the largest configuration that ALMA can support, with antennas spread over distances up to 16 km. The array thus simulates a giant, single telescope much larger than any that could actually be built. In fact, ALMA has a maximum resolution which is even better than that achieved, at visible wavelengths, by the Hubble Space Telescope.

The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of radio telescopes in the Atacama desert of northern Chile. Since a high and dry site is crucial to millimeter wavelength operations, the array has been constructed on the Chajnantor plateau at 5,000 meters altitude, near Llano de Chajnantor Observatory and Atacama Pathfinder Experiment. Consisting of 66 12-meter (39 ft), and 7-meter (23 ft) diameter radio telescopes observing at millimeter and submillimeter wavelengths, ALMA is expected to provide insight on star birth during the early universe and detailed imaging of local star and planet formation. ALMA is a single telescope of revolutionary design, composed initially of 66 high-precision antennas, and operating at wavelengths of 0.32 to 3.6 mm. Its main 12-meter array has fifty antennas, 12 meters in diameter, acting together as a single telescope — an interferometer. An additional compact array of four 12-meter and twelve 7-metre antennas complements this. The 66 ALMA antennas can be arranged in different configurations, where the maximum distance between antennas can vary from 150 metres to 16 kilometres, which will give ALMA a powerful variable “zoom”. It will be able to probe the Universe at millimetre and submillimetre wavelengths with unprecedented sensitivity and resolution, with a vision up to ten times sharper than the Hubble Space Telescope, and complementing images made with the VLT Interferometer. Light at these wavelengths comes from vast cold clouds in interstellar space, at temperatures only a few tens of degrees above absolute zero, and from some of the earliest and most distant galaxies in the Universe. Astronomers can use it to study the chemical and physical conditions in molecular clouds — the dense regions of gas and dust where new stars are being born. Often these regions of the Universe are dark and obscured in visible light, but they shine brightly in the millimeter and submillimetre part of the spectrum.

ALMA is the most powerful telescope for observing the cool Universe — molecular gas and dust. ALMA will study the building blocks of stars, planetary systems, galaxies and life itself. By providing scientists with detailed images of stars and planets being born in gas clouds near our Solar System, and detecting distant galaxies forming at the edge of the observable Universe, which we see as they were roughly ten billion years ago, it lets astronomers address some of the deepest questions of our cosmic origins.

Image taken taken in 14/10/2015 from Chajnantor plateau, Atacama desert, Chile.

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