ALMA Opens Its Eyes to First Light

The Atacama Large Millimeter/submillimeter Array (ALMA), the most powerful telescope of its kind in the world, has revealed its first image.

About one-third of ALMA's eventual 66 radio antennas, with separations up to only 125 m rather than the maximum 16 km, make up the growing array on the Chajnantor plateau in northern Chile, at an elevation of 5000 m. And yet, even under construction, ALMA has become the best telescope of its kind — as reflected by the extraordinary number of astronomers who have requested time to observe with ALMA.

The Antennae Galaxies (also known as NGC 4038 and NGC 4039) are a pair of distorted colliding spiral galaxies about 70 million light-years away, in the constellation of Corvus (The Crow). This view combines ALMA observations, made in two different wavelength ranges during the observatory's early testing phase, with visible-light observations from the NASA/ESA Hubble Space Telescope. (Image: ALMA (ESO/NAOJ/NRAO) and the NASA/ESA Hubble Space Telescope)

"Even in this very early phase, ALMA already outperforms all other submillimeter arrays. Reaching this milestone is a tribute to the impressive efforts of the many scientists and engineers in the ALMA partner regions around the world who made it possible," said Tim de Zeeuw, director general of the European Southern Observatory (ESO), the European partner in ALMA.

ALMA is radically different from visible-light and infrared telescopes. It is an array of linked antennas acting as a single giant telescope, and it detects much longer wavelengths than those of visible light. Using longer wavelengths allows astronomers to study extremely cold objects in space — such as the dense clouds of cosmic dust and gas from which stars and planets form, as well as very distant objects in the early universe.

The ALMA team has been busy testing the observatory’s systems over the past few months, in preparation for the first round of scientific observations, known as Early Science. One outcome of their tests is the first image published from ALMA, albeit from what is still very much a growing telescope. Most of the observations used to create this image of the Antennae Galaxies were made using only 12 antennas working together — far fewer than will be used for the first science observations — and with the antennas much closer together as well. Both of these factors make the new image just a taste of what is to come. As the observatory grows, the sharpness, efficiency and quality of its observations will increase dramatically as more antennas become available and the array grows in size.

The Antennae Galaxies are a pair of colliding galaxies with dramatically distorted shapes. While visible light shows us the stars in the galaxies, ALMA's view reveals something that cannot be seen in visible light: the clouds of dense, cold gas from which new stars form. This is the best submillimeter-wavelength image ever made of the Antennae Galaxies.

During its Early Science observations, ALMA will continue its construction phase in the Chilean Andes. Each new climate-armored antenna will join the array and be linked via fiber optic cabling. The views from each distant antenna are assembled into one large view by one of the world’s fastest special-purpose supercomputers, the ALMA correlator.

For more information, visit: www.eso.org/alma