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Discoveries begin as ALMA officially opens

Paul Sutherland, Feature writer
Mar 19, 2013, 7:00 UTC

Sen—The world’s highest observatory was officially opened last week in a grand ceremony - but ALMA, high in the Chilean Andes, has already been making new discoveries about the Universe for months.

President of Chile Sebastián Piñera welcomed several international ministers plus other VIPs, science leaders and journalists to the control centre for the Atacama Large Millimeter/submillimeter Array.

He told them: “One of our many natural resources is Chile’s spectacular night sky. I believe that science has been a vital contributor to the development of Chile in recent years. I am very proud of our international collaborations in astronomy, of which ALMA is the latest, and biggest outcome.”

But even as he spoke, Nature and the Astrophysical Journal were publishing results of a major study by ALMA revealing that the most vigorous bursts of star birth in the Universe took place much earlier than previously thought.

The most intense bursts of star birth are believed to have occurred in the early cosmos, in massive, bright galaxies. These starburst galaxies can be observed to be converting vast quantities of gas and dust into new stars at a furious pace — many hundreds of times faster than in spiral galaxies like our own Milky Way.

By peering far into space, at galaxies so distant that their light has taken many billions of years to reach us, astronomers can observe this busy period in the Universe’s youth.

Galaxies from ALMA and HubbleImages of three galaxies, in red, from ALMA are combined with images from the the Hubble Space Telescope. The more distant galaxies are distorted by gravitational lensing. Credit: ALMA (ESO/NRAO/NAOJ), J. Vieira et al

The astronomers used just a partial array of 16 of ALMA’s full complement of 66 giant antennas, as the observatory was then still being built 5,000 metres high on the remote Chajnantor Plateau.

Joaquin Vieira, of the California Institute of Technology, was leader of the study team. He said: “The more distant the galaxy, the further back in time one is looking, so by measuring their distances we can piece together a timeline of how vigorously the Universe was making new stars at different stages of its 13.7 billion year history.”

They were surprised to find that many of these distant dusty star-forming galaxies are even further away than expected. This means that, on average, their bursts of star birth took place 12 billion years ago, when the Universe was just under 2 billion years old — a full billion years earlier than previously thought.

Two of these galaxies are the most distant of their kind ever seen — so distant that their light began its journey when the Universe was only one billion years old. In one of them, water is among the molecules detected, marking the most distant observations of water in the Universe published to date.

Dr John Richer, UK Project Scientist on ALMA, said of the findings: “It’s fantastic to see the first incredible images of the early Universe coming out of the ALMA observatory.

Gravitational lensingDiagram showing how gravitational lensing distorts a background galaxy. Credit: ALMA (ESO/NRAO/NAOJ), L. Calçada (ESO), Y. Hezaveh et al.

“From the very earliest days of its design, we anticipated that ALMA would be the key to unlocking the secrets of how the Universe evolved to forms stars and galaxies soon after the Big Bang. These beautiful studies justify that view, and demonstrate how ALMA’s unique images of the distant Universe are starting to revolutionise our understanding of our cosmic origins.”

Professor Scott Chapman, of the UK’s University of Cambridge, led observations in the optical and infrared that helped build to the latest discovery.

He said: “There has long been debate over the origins of stars in galaxies. Are they born over long periods of time or in concentrated bursts? With ALMA, we have measured huge numbers of stars forming rapidly in a short period of time about 12 billion years ago, a billion years earlier than previously thought.”

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ESO video about the inauguration of ALMA. Credit: ALMA (ESO/NAOJ/NRAO)