What is the best place in the world to observe the sky? Tradtiionally astronomers prefer the tops of high mountains. Why? Because the altitude minimises atmospheric distortion of telescopic images, and because mountains are usually far from the light-polluted skies of the cities. And ideally the mountain should also be in a desert, where low water vapour levels in the atmosphere contribute greatly to clearer viewing conditions. This is why the Atacama Desert in Chile, for example, is home to a number of major telescopes such as ALMA (see my last post) and the Very Large Telescope.
But in recent years another even more remote location has become increasingly popular with astronomers – Antarctica. It meets all the requirements listed above – high altitude, arid conditions and no light pollution. Plus it has certain other advantages: the polar location means that there are months of continuous darkness in the winter, and the stars around the pole stay in much the same position during this period, never setting, meaning that observations can be made for very long periods without a break. And the ice itself can be an avantage in some observations as explained below.
Most of the astronomical facilities in Antarctica are located at the Amundsen-Scott South Pole Station. With a 10-meter primary mirror, the largest telescope there is the South Pole Telescope, completed in 2007. It observes at millimetre wavelengths and is designed to observe the Cosmic Microwave Background (CMB), very faint radiation permeating the whole sky that is a relic from the infant universe not long after the Big Bang.
The South Pole is also home to another facility designed to observe the CMB – the Keck Array. This suite of five telescopes is specially designed to measure polarisiation in the CMB. The aim is to find clues in this data about the period known as ‘Inflation’ during the very early universe, when the whole universe is believed to have expanded exponentially in a period briefer than the blink of an eye.
A different type of astronomy
Perhaps the most intriguing and unusual astronomical facility in Antarctica is the IceCube project, which is actually not a telescope at all. It is an array of 500 sensors located into a network of 86 holes holes drilled 2.4 km deep into the solid ice, and it covers a cubic kilometre in total, hence the name.
It is an observatory designed to detect not light waves but neutrinos: high energy particles that are created by violent astronomical events such as exploding stars. Neutrinos are one of the most common fundamental particles and our world is exposed to a constant stream of them but they are very poorly understood because they are really difficult to observe - they virtually never interact with matter, they just pass straight through leaving no trace at all.
However, very occasionally a neutrino will interact, leaving a dim bluish glow known as Cherenkov radiation, and IceCube is designed to detect this effect. The IceCube sensors are buried deep in the transparent ice, in order to minimise atmospheric contamination from other particles originating in the atmosphere that can produce the same effect.
This ambitious project announced its first success in July this year - the detection of one of these elusive particules
and the tracing of it back to its source, a distant flaring black hole known as a ‘blazar’ located around 3.7 billion light years away. This first achievement in the newly developing branch of neutrino astronomy, could herald the opening a whole new window on our universe.
https://pole.uchicago.edu/public/ (The South Pole Telescope)
https://www.cfa.harvard.edu/CMB/keckarray/
https://www.space.com/42202-why-we-need-cosmic-inflation.html
https://icecube.wisc.edu/about/overview
https://earthsky.org/space/icecube-observatory-detects-neutrino-blazar-source
1. Dr. Keith Vanderlinde, NSF https://photolibrary.usap.gov/PhotoDetails.aspx?filename=POLENIGHTSKY1.JPG
2. Jamie Yang, IceCube Collaboration https://icecube.wisc.edu/gallery/press/view/1336
3. IceCube/NASA https://icecube.wisc.edu/news/view/586