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ALMA's breakthrough in measuring up stellar nurseries

Paul Sutherland, News Editor
22 September 2012, 23:00 UTC

Sen— Astronomers have made a breakthrough in understanding the chemistry of the Universe thanks to the tremendous power of the European Southern Observatory's revolutionary ALMA telescope in Chile's Atacama Desert.

By combining the capabilities of the array of dishes 5,000 metres above sea level with newly-developed lab techniques, the scientists have begun what they are heralding as a new era in deciphering interstellar elements.

The new methods are allowing astronomers to analyse what was an overwhelmingly complex amount of spectral information from space and to identify quickly the "fingerprints" marking out different chemicals in the cosmos.

Such studies, which before would have been either impossible or prohibitively demanding timewise, have been successfully demonstrated on one of the most famous cosmic nurseries the Orion Nebula, M42, which is a cloud of dust and gas incubating new-born stars.

The results have been achieved while the observatory is still under construction. Around 45 high-precision dishes have been delivered so far but by the end of next year, 66 will be operating high up on the Chajnantor plain which Sen visited for a special report last year.

They observe the Universe between longer-wavelength radio and the infrared, a special zone of the spectrum that is rich in information about the presence of specific molecules in space, some of which are needed for life to form.

Astronomers have discovered more than 170 molecules, including organics such as sugars and alcohols, and they are common in the giant clouds of gas and dust where stars and planets form. Thomas Wilson of the Naval Research Laboratory in Washington, D.C., said: "We know that many of the chemical precursors to life exist in these stellar nurseries even before the planets form."

The Orion Nebula

Astronomers have matched the signatures of chemicals in the lab (blue) with those observed in the Orion Nebula by ALMA (red). Credit: Fortman, et al., NRAO/AUI/NSF, NASA

Molecules in space identify themselves as groups of lines in the spectrum. Each has a different pattern and it can usually be an extremely challenging task to identify them. The breakthrough has come thanks to new technology that allows scientists to analyse and identify several patterns at once.

Patterns observed under lab conditions are compared to observations of star-forming regions using ALMA and matches found.

Frank DeLucia of the Ohio State University said: "We now can take a sample of a chemical, test it in the laboratory, and get a plot of all its characteristic lines over a large range of wavelengths. We get the whole picture at once. We can then model the characteristics of all the lines of a chemical at different temperatures.

Paul Sutherland at ALMA

Sen writer Paul Sutherland at ALMA in 2011. Credit: Emily Baldwin

"In the past, there were so many unidentified lines that we called them 'weeds,' and they only confused our analysis. Now those 'weeds' are valuable clues that can tell us not only what chemicals are present in these cosmic gas clouds, but also can give important information about the conditions in those clouds."

Suzanna Randall of ESO Headquarters in Garching, Germany, said: "This is a new era in astrochemistry. These new techniques are going to revolutionize our understanding of the fascinating nurseries where new stars and planets are being born."

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