FAQ APEX/ALMA

  1. How do ESO’s infrared and (sub) millimetre wavelength telescopes help us study how stars form?
  2. What do you mean when you say that the APEX and ALMA telescopes can be used to look for molecules in space?
  3. How big are the ALMA transporters, and how powerful are their engines?
  4. Will APEX become part of ALMA in the future?
  5. Do we obtain images by observing submillimetre-wavelength light?
  6. Is ALMA better than the telescopes at Paranal because it is located at a much higher site?
  7. How is energy produced at ESO’s Observatories?
  8. Why is solar energy not used at ESO’s observatories?
  9. What is ESO's share in ALMA construction cost?
  10. What are ESO's major contributions to the ALMA project?

Q: How do ESO’s infrared and (sub) millimetre wavelength telescopes help us study how stars form?

A: Stars form in dense clouds of the interstellar medium, but even in the densest of these regions the pressure is comparable to the most tenuous vacuum created in a laboratory on Earth. These clouds, where the temperatures are below -200 degrees Celsius are opaque in visible light, but transparent at longer wavelengths, like infrared, millimetre and submillimetre radiation. Telescopes such as VISTA, APEX and ALMA are vital for studying these cold, dense sites of star birth.

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Q: What do you mean when you say that the APEX and ALMA telescopes can be used to look for molecules in space?

A: Many molecules have been detected as constituents of giant gas clouds in space, from simple molecules like water, up to more complex organic compounds including amino acids. They tend to form and survive in these relatively cold and dense environments, where they are not exposed to high energy radiation. For example, there is an Earth-mass of alcohol near the centre of our Milky Way galaxy. However, most of it is methanol, and it is diluted to one part in a thousand with water. Telescopes observing at millimetre and submillimetre wavelengths, like APEX and ALMA, are used to detect these and many other molecules in space.

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Q: How big are the ALMA transporters, and how powerful are their engines?

A: The ALMA transporters are two unique vehicles, specifically designed to carry antennas which weight more than 100 tonnes each, at 5000 metres altitude. Each of the transporters weighs 132.5 tonnes and have twin engines rated at 500 kW each (at sea level). This gives a total of about 1400 horsepower.

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Q: Will APEX become part of ALMA in the future?

A: APEX is based on a prototype antenna constructed for the ALMA project, but it was designed to operate as a single dish, and it is not planned to integrate it with ALMA. However, APEX's wide field of view will find many targets that ALMA can study in great detail, so the two observatories will complement each other in the exploration of the millimetre and submillimetre Universe.

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Q: Do we obtain images by observing submillimetre-wavelength light?

A: Yes, although this radiation may not be visible to human eyes, we can image the Universe using radiation with wavelengths far beyond those of visible light. For example, the Large APEX Bolometer Camera LABOCA, is an invaluable tool for imaging the submillimetre-wavelength Universe. LABOCA uses an array of extremely sensitive “thermometers” known as bolometers to detect submillimetre light. With almost 300 pixels, it is the largest such camera in the world. In order to be able to detect the tiny temperature changes caused by the faint submillimetre radiation, each of these thermometers is cooled to less than 0.3 degrees above absolute zero — a frigid minus 272.85 degrees Celsius.

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Q: Is ALMA better than the telescopes at Paranal because it is located at a much higher site?

A: The VLT and ALMA are the most powerful telescopes in the world of their kinds. As they observe the Universe at different wavelengths, they are in fact complementary. The Earth's atmosphere is much less transparent to the millimetre and submillimetre radiation observed by ALMA than to visible light. Since water vapour strongly absorbs these wavelengths, it is critical for ALMA to be located in a very high and dry place. These requirements are perfectly met on the Chajnantor plateau, at an elevation of 5000 metres in the Chilean Andes.

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Q: What is ESO's share in ALMA construction cost?

A: ESO share in ALMA construction cost is 37.5%.

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Q: What are ESO's major contributions to the ALMA project?

A: ESO's major contributions to the ALMA project include:

    • 25 of ALMA’s 12-metre dish antennas
    • The ALMA Antenna Transporters (Otto and Lore)
    • Antenna Water Vapour Radiometers
    • Roads from the entrance gate to the Operation Support Facility (OSF), and from the OSF to the Array Operation Site (AOS)
    • The OSF Technical Building
    • The permanent power supply (turbine generators)
    • The ALMA Residencia (visitor living quarters, under development)
    • Band 7 receiver cartridges
    • Band 9 receiver cartridges
    • Front End Power Supplies
    • Front End Cryostats
    • Front End integration
    • Back End components and Optical-Digital Transmission System • Tunable Filter Bank Cards for the 64-Antenna Correlator
    • AOS Antenna Pads and Interfaces
    • Software
    • Support for European ALMA users via seven European ALMA Regional Center nodes

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