Tuesday, October 16, 2012

Astrochemistry at ALMA

"The Atacama Large Millimeter/sub-millimeter Array (ALMA) is an array of radio telescopes in the Atacama desert of northern Chile. Since a high and dry site is crucial to millimeter wavelength operations, the array is being constructed on the Chajnantor plateau at 5000 metres altitude. Consisting of 66 12-meter and 7-meter diameter radio telescopes observing at millimeter and sub-millimeter 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 an international partnership between Europe, the United States, Canada, East Asia and the Republic of Chile.

Costing more than a billion US dollars, it is the most expensive ground-based telescope currently under construction. ALMA began scientific observations in the second half of 2011 and the first images were released to the press on 3 October 2011. The project is scheduled to be fully operational by the end of 2012."
Acatama Large Millimeter/submillimeter Array ALMA home.

Astrochemistry Enters a New Bold Era with ALMA
"Combining the cutting-edge capabilities of the ALMA telescope with newly-developed laboratory techniques, scientists are opening a completely new era for deciphering the chemistry of the Universe. A research team demonstrated their breakthrough using ALMA data from observations of the gas in a star-forming region in the constellation Orion.

Using new technology both at the telescope and in the laboratory, the scientists were able to greatly improve and speed the process of identifying the "fingerprints" of chemicals in the cosmos, enabling studies that until now would have been either impossible or prohibitively time-consuming.

“We've shown that, with ALMA, we're going to be able to do real chemical analysis of the gaseous 'nurseries' where new stars and planets are forming, unrestricted by many of the limitations we've had in the past,” said Anthony Remijan of the National Radio Astronomy Observatory in Charlottesville, VA."
ALMA Press release September 20 2012 

How ALMA works?
Two antennas linked together as interferometer
"In theory, the basic notion of interferometry is quite simple.

A signal from the sky is captured by two or more antennas which are combined in order to analyze the signal and thus obtain information about its source (whether a star, a planet, or a galaxy). By combining the radio waves collected by several antennas, it is possible [to create] images...

Nevertheless, this is not so simple in practice.

To operate properly, ALMA

  • must have its 66 antennas and electronics working in perfect synchrony, with a precision of one millionth of a millionth of a second. 
  • the signals from the different antennas must be combined in a way that the path followed from each antenna until it is combined at the central computer (the correlator) must be known with an accuracy equal to the diameter of a human hair (hundredths of a millimeter). 
  • there is the problem of reducing the possible attenuation and perturbation suffered by the signal from the time it touches each antenna until it is digitalized and transmitted over several kilometers of optic fiber to the central computer. 
  • Even earlier, as soon as the signal penetrates the Earth’s atmosphere, it is partially absorbed, deviated and delayed by molecules of CO2, Oxygen and water (even at 5,000 m of altitude and in the dry conditions encountered at the Atacama Desert). 
Seven weather stations, and specially-built Water Vapor Radiometers to measure the amount of line-of-sight water vapor present in the atmosphere, will be used to correct for these atmospheric effects."
Read the entire article by Antonia Hales

ALMAnize your Google Earth

Download this file to personalize your Google Earth and easily place ALMA on the globe.

Once you open it, the ALMA facilities and the current position of the antennas will appear to you as marked.

A cool way to include the observatory that brings you closer to the Universe on your virtual journey !

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