Astronomy on ice

Ken Tapping, May 23, 2012

In the sky this week…

  • Venus still dominates the western sky after sunset.
  • Mars is high in the South; Saturn is in the eastern sky.
  • The Moon will reach First Quarter on May 8.

It must be one of the most inhospitable locations on Earth. Temperatures can be as high as −20°C and dip down below −60°C. It lies nearly 2900 metres above sea level. It is very dry. Snow rarely falls; most of the bad weather comes from ice crystals blowing along the ground. Because it is so cold, the ice crystals are perfectly dry, and the electrostatic sparks produced when they rub together can make radio reception difficult. Another problem is making precision machinery operate reliably under very hostile conditions. Getting there is expensive, and almost everything needed has to be flown in. For roughly half of each year the Sun doesn’t rise and for most of the other half it does not set. Of course we’re discussing the South Pole, in Antarctica, and despite those shortcomings, it is an excellent place for astronomy and space science.

Firstly, the site is high and dry, so the sky is clear enough for high-quality astronomy, including observing at wavelengths that at more temperate locations are blocked by water vapour. It can be as dark as it gets anywhere, with no human settlements other than the scientific research stations. The sky does not glow with back-scattered street and city lights. In addition, with no neighbours, there is no problem with installing scientific instruments, stringing long antenna wires, or setting up a cubic kilometre of ice as a huge neutrino telescope. With darkness for much of the year, our observing sessions can be much longer than they are elsewhere. We can study very faint objects and record rapidly-varying ones without losing them in the daylight for half of each day. One of the main areas of interest to which the South Pole is well-suited is cosmology: the study of the origin of the universe and how that early universe became the one we see around us today.

The pulse of radiation produced when the universe was born and during its extremely hot early youth is trapped within and is still observable. Over the almost 14 billion years since the Big Bang, the universe has expanded a lot and cooled down, but that radiation is still observable and can be mapped. In those maps small temperature variations reveal the first signs of embryo galaxies. These small fluctuations can be detected more easily though techniques such as interferometry, where multiple telescopes are combined.

The South Pole is an ideal place for cosmological research. The clear, dry sky and long hours of darkness provide opportunities to make observations that would be difficult or impossible anywhere else. Many of these experiments involve clusters of antennas resembling ice cream cones of various sizes, fixed so they are perpetually looking straight up. This is convenient because the Antarctic is hard on things with many moving parts.

Roald Amundsen was the first explorer to reach the South Pole; Robert Scott died becoming the second. Now, that place is the site of the Amundsen-Scott South Pole Station, and a jumping-off point for more exploration.

Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory, Penticton,  BC, V2A 6J9.

Telephone: 250-497-2300
Fax: 250-497-2355
E-mailken.tapping@nrc-cnrc.gc.ca

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