The principal obstacle for astronomers is the Earth's atmosphere which has three main effects: it is absorbing, emissive and turbulent. This is why astronomers choose to set up their observatories on high mountains (such as Mauna Kea in Hawaii, or the Andes), send them aloft on planes or balloons, or even send them into space on rockets or satellites. Its high altitude (3000 to 4000m) and its cold and dry air give the antarctic plateau unique astronomical conditions, somewhere between space and the best currently-exploited sites on the ground.
At Dome C, the atmosphere is transparent to the large wavelengths
With less water vapor and aerosols than these current sites, the atmosphere above Dome C opens new spectral windows for astronomical observations, mainly in the infrared at wavelengths of 1 to 40 microns, and in the submillimetre-wave domain between 100 microns and 1 mm. The majority of the Earth's atmosphere, consisting of 78% nitrogen and 21% oxygen, is similar everywhere on Earth. The remaining minority components, however, such as water vapor (H2O), carbon dioxide (CO2) and aerosols, vary from one site to another and vary with altitude, yielding a variable atmospheric transmission. In the infrared range, astronomical observations are also limited by the thermal radiation of the sky itself. Water molecules and aerosols emit light at these wavelengths, potentially dazzling astronomical detectors. Levels of aerosols ? produced by human activities and volcanos ? are very low at Dome C because of its distance from most of the human population and because jet streams keep weather systems out of the Antarctic continent. The very low water vapour content of the air also allows submillimetre-wave radiation to be transmitted, particularly in the spectral windows at 200, 350 and 450 microns.
<>
? M.G. Burton et al (2005)
Comparison of the atmospheric transmission between the site of Mauna Kea in Hawaii (in red) and the Dome C (in blue) for wavelengths ranging between 2.4 microns (near infrared) and 500 microns (submillimetric). At Dome C, the already existing windows down to 30 microns are increasing, and new windows has been opening from 50 to 500 microns.
Consequently, new spectral windows are open at Dome C and those already in use at other sites are broader.In addition to the remarkable atmospheric transmission at Dome C, the lack of a day/night cycle allows uninterrupted observations over long periods. These two distinct properties of the site offer unique and exciting astrophysical prospects.
? E. Aristidi
At Dome C, temperatures can reach -80?C? Thus, the atmosphere contains very few water vapor and aerosols which retain heat. Consequently, the site of Dome C is ideal to carry out astronomical observations in the infra-red and in the submillimeter wave range.
){kind=spacer}
)
