Skip to navigation | Skip to content

Dome C: Window to the stars

Throughout history, people have been searching for the best place to look at the stars. In January 2003, a team of astrophysicists from the University of New South Wales set off to prove that this place is Dome C, Antarctica.

the horizon

Searching the horizon for, among other things, extraterrestrial life(Source: UNSW, School of Physics)

Dome C is one of the most barren places in the world. As one visitor said: "Once you've seen the horizon, you've seen everything." Rising like a scene from Star Wars in the middle of this vast white desert is a cluster of odd shaped buildings and a couple of skidoos. Looking at it, it is hard to see what Dome C could possibly contribute to our never ending study of the universe and the search for extraterrestrial life.

The South Pole traditionally, has been an ideal place for astronomical measurements. However, with plans underway for a new multi million dollar observatory, some astronomers are questioning whether it is the best place after all.

"The only reason why the South Pole exists as a station is a quirk of cartography," says Andre Phillips, a research associate at Siding Spring Observatory. "There are other places, better places in Antarctica for astronomical research and the key word is Dome".

^ to top

Selection criteria

So why is Dome C better than anywhere else on the planet for an astronomical observatory? It fits two essential criteria: dry and still.

Dryness is important because water vapour in the air absorbs particular electromagnetic wavelengths that come from outer space before they reach the surface of the Earth. These wavelengths carry information in the invisible part of the spectrum. If the air is extremely dry, these wavelengths will reach the earth and can be detected by astronomical instruments such as telescopes.

The Antarctic plateau is the driest place on earth, with precipitation levels lower than the Sahara Desert. Dome C is particularly dry because it is very high - over 3,200m. The Antarctic plateau has an area larger than Australia, all of which stands at a higher altitude than Mount Kosciusko. The higher you get the colder and drier it becomes. Once the problem of water vapour is removed, whole new windows of the invisible spectrum will be opened, such as the infrared and sub-millimetre, and it is in these spectral ranges that astronomers believe there will be huge advantages for astronomy.

The other criterion, stillness or a complete absence of wind, is more problematic. Wind at high altitudes and the turbulence that results from that wind is the major obstacle to making ultra-precise astronomical measurements.

"When we say to other astronomers what we're trying to do, they laugh," says John Storey, leader of the Dome C project and Head of Physics at UNSW. "They say, don't be ridiculous; Antarctica is too windy. But they don't understand that Antarctica is only windy along the coast. In the centre it's dead calm."

Tony Travouillon is doing his PhD on the wind turbulence at Dome C. He has set up an acoustic radar to measure the turbulence of the first kilometre of the atmosphere.

"Turbulence is a problem because it gives stars artificial movement when you look at them through a telescope," says Travouillon. "In Antarctica, the katabatic winds [rushing cold winds that fly down a sloped plane, displacing warmer air below] start at the highest points and gather force and speed as they are driven by gravity towards the coast. Since Dome C is one of the highest points, the wind speed most of the time is close to zero."

^ to top

The green tomato

The instrument that will be making these crucial measurements is a green plastic igloo, technically known as the AASTINO (or mini Automated Astrophysicsal Site-Testing Observatory) and more affectionately known as the 'green tomato'. The AASTINO will be left on its own during winter and will transmit information via a satellite phone. Storey hopes that by the end of this year they will know for certain that Dome C is the best site on Earth for an astronomical observatory.

"It's bloody amazing what they're getting away with," says Phillips. "Automatic geophysical observatories left unattended in Antarctica have had a very poor rate of success, and the problem is the power supply."

In Antarctica the sun sets for 6 months over winter, making solar power impossible, the wind is either too weak, or strong enough to blow a wind generator apart, and propane powered thermoelectric generators are prone to explode. AASTINO however, is running on a type of jet fuel, which is the source of power for everything at Dome C from jet planes to kitchen stoves. The fuel can resist temperatures of up to -50oC, but over winter must be kept inside the igloo, safe from outside temperatures of -80oC.

^ to top

The race is on

"The only reason we're the first ones to do these things at Dome C is because no one really twigged to this idea before we did," says Storey. "So now we're rushing there as fast as we can in order to nail down these numbers. Around the world, everyone's waiting to see what we come up with."

Phillips agrees. "If they can prove Dome C is what they think it is, it could cause a scientific stampede from the astronomical, atmospheric and space science community. It could be the beginning of the most exciting science that's happened in Antarctica for years."

The French and Italian programs are already planning to open a station that will run all year round, making Dome C the next logical place for a multi million dollar observatory. The observatory will be an international collaboration, but the real race is in each country persuading their respective governments to fund the observatory. Whichever government puts forward the largest amount of money will effectively have the controlling interest in the telescope and make most of the decisions.

And how is Australia looking as a contestant?

"A bit shaky at the moment," says Storey. "The main obstacle is the cost. But it's cheaper to build a telescope at Dome C than it is to build one in Sydney. If we can sway the government to cough up A$7.5 million, we can get the other A$20 million from other sources."

This will make Australia a 50% shareholder with the Europeans. Australia traditionally has not been able to afford to participate in space programs on the scale of the Europeans and the Americans. Dome C may be a way for Australia to contribute to major astronomical discoveries and research.

^ to top

The truth is out there

One of the most frequently asked questions in astronomy is: Are we alone? Or are we just one of millions of civilisations?

The first prerequisite to life is a planet that is habitable. Life on a star is impossible because the temperatures are too high. The planet must be the right distance from the star, the right temperature, and have an atmosphere where biological processes can take place. It was only seven years ago that astronomers discovered the existence of other planets around other stars. So, for the first time, astronomers can begin to seriously consider where our nearest galactic neighbours might be living.

In seven years, over a hundred planets have been discovered. They were found by measuring the Doppler shift, where the star wobbles back and forth along the line of sight. The only reasonable explanation for the wobble is that a planet in orbit around the star is causing the star to move back and forth. So by ultra precise measurements of the star's position and its wobbles, astronomers can detect the presence of planets.

Most of the planets detected so far have been giant Jupiter sized planets and almost all of them orbit close to their star. Astronomers have not yet detected a habitable planet, although by improving instrumentation and placing observatories in better sites, astronomers hope this is not too far away.

Another technique to detect planets is the eclipse technique, which requires an exceptionally stable sky. If a planet in orbit around a star moves across the face of the star, there will be a very tiny drop in the brightness of the star as its light will be blocked by the planet. By monitoring a star and its brightness very carefully, astronomers can detect this tiny change in brightness.

Doug Caldwell is part of the NASA planet search program. He says, "We currently use the South Pole for the planet search telescope because of the year round station that provides power and communications. In the future, however, Dome C could be the ideal place from which to look for planets."

Storey argues that both the Doppler technique and the eclipse techniques will be much more effective at Dome C, which may lead to the discovery of more planets.

^ to top

The final countdown

Storey hopes the data that will ensure Dome C's place in astronomical history will be confirmed by 2004, and the question of turbulence will be answered as early as the end of 2003. In 2005 around eight people will be the first ever humans to spend a winter at Dome C.

Is there anything else Dome C has in store for us? Storey grins.

"Everyone knows as soon as all the people leave Dome C, the aliens move in. So we've set up a web cam this winter so we can see the aliens when they arrive."

And that address? Stay tuned for more developments at the alien seeking, planet hunting, astronomical marvel of Dome C.

Tags: astronomy-space

^ to top

Published 17 May 2003