25 August 2008

Telescope on the Greenland ice cap

Summit, on the middle of the ridge of the 3 kilometer thick ice cap in Greenland could be a new scientific centre for astronomical observations in the northern hemisphere.

Astrophysicist Kristian Pedersen has just returned from an expedition to Greenland – tanned and a little bit long-bearded “as one should be when one is on the ice cap in Greenland”, he says and chuckling a little. Normally it is not the cold regions he travels to when observing space, rather warm places like the large observatories in Chile and the Canary Islands. But now the Greenland ice cap could be a new, attractive location to install a large telescope.

Sharpest images
“On the top of the ice cap the weather is very stable, the air is dry and calm, there is total darkness half of the year, and it is perhaps one of the places on earth where you can take the sharpest images of the universe”, explains Kristian Pedersen, who is an astrophysicist at the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.

Danish astronomers have discussed for many years the idea that Greenland could be a good place to observe, but no measurements were ever made. But a grant from the Instrument Center for Danish Astrophysics (IDA) made it possible to investigate whether there was good potential for building a telescope at the site. For this purpose, a special telescope was designed by astronomer Michael I. Andersen and was built by Anton Norup Sørensen, a technician at the Niels Bohr Institute, who is an expert in cameras for astronomical telescopes.

Placed in a high tower
On the 20th of July they traveled to Greenland – in the best scouting manner, on with the hiking boots (polar boots loaned from ice core researchers at the Niels Bohr Institute) a telescope in the rucksack, and the two were ready to take to the field. From Kangerlussuaq they flew with an American Hercules plane to Summit, where the Americans have a research base. At the base there is also a 50 meter tall tower, which is used by Swiss climate researchers and that is where the Danish telescope was to be placed. There is too much turbulence in the air at the surface, so the telescope needed to be 40 meters up in the tower.

“Anton crawled up in the tower to mount the telescope while I sat in a warm tent on the ice and controlled the alignment”, explains Kristian Pedersen. The telescope was a 20 cm reflecting telescope and needed to be adjusted to point towards the North Star. The measurements from this year are meant to show the sharpness of the images from the observation site, and will therefore only observe the North Star.

Observations of distant galaxies
Because it is so cold at the site – reaching minus 60 degrees in the winter, there is very low infrared radiation and that is important in order to observe far back in the history of the universe. The farther you go back in time the more long waved light is, the more infrared it is. With a large telescope of 3-4 meters in diameter one will be able to see, using infrared light, the very first and most distant galaxies in the universe.

Such is the dream. But first, the images from the year’s test observations need to be analyzed and then astronomical test observations over a longer period will need to be performed. The intention is, that the measurements will take place during the winter half-year, when it is dark around the clock and as the telescope needs to function automatically, it will only observe the North Star as a fix-point.

A large telescope on the ice cap could supplement the new space telescope, the James Webb Space Telescope, which will be launched in 2013. It will be very sensitive, but has a small field of vision, which makes it possible for it to study few objects in great detail. The telescope on the ice cap, on the other hand, could find many objects and the most interesting can then be studied more closely from the space telescope.