Frigid temperatures, dry air, and endless nights should, in theory, make the polar regions top spots for ground-based optical astronomy. So far, Antarctica has been getting all the action, with roughly a handful of optical telescopes peering into the sky from the icy continent. But a new study indicates that the Canadian high Arctic is also a good spot for ground-based optical astronomy. In fact, the great white north offers some practical advantages over the Antarctic.
"The explosion of good optical astronomical work in Antarctica gave us an incentive to look more carefully at doing something similar in Canada," says Eric Steinbring, an astronomer at the Herzberg Institute of Astrophysics in Victoria, Canada, and lead author of the study, in press at Publications of the Astronomical Society of the Pacific. The paper documents the first professional astronomical observational data using an all-sky, wide-field camera mounted under a Plexiglas dome on the roof of Canada's Polar Environment Atmospheric Research Laboratory (PEARL) at 80° north latitude, a site previously used only for atmospheric environmental research.
Comparing the brightness of two neighboring stars, the researchers found that the site would be good for high-quality photometry—measuring the total light from a given target and how it varies over time—due to the site's very clear, dark skies. Other instruments in a related study show that the Arctic site appears not to suffer from the strong low-level atmospheric turbulence found on the Antarctic plateau, which can distort image quality. And the low sky brightness in the visible spectrum suggests the site would also be a good near-infrared astronomical site, as obscuring infrared emissions from the sky itself would be relatively weak. The cold location could even help cool a telescope's mirror and limit the infrared glow from the instrument itself.
"Canada as a whole is not a great place for optical astronomy," Steinbring says. At lower latitudes, clouds frequently cover the sky, but at the PEARL location, skies in winter are cloudy only 14% of the time, he says. The study found that spectroscopy can be done at the site 68% of the time and high-precision photometry about half the time. To see how sensitive and accurate observations made at the site could be, the astronomers trained their sights on Polaris, the variable pole star. They were able to make out the previously observed waxing and waning of the star's brightness, which repeats every 4 days. And unlike Antarctica, the Canadian site is accessible via road and has an all-weather airstrip large enough for jet aircraft.
And at least some astronomers are coming. The University of Toronto's (UT's) Dunlap Institute for Astronomy and Astrophysics is installing a $100,000 robotic 0.5-meter-optical telescope at the site this summer. First light is expected by the end of the year. "We're starting out with a search for extrasolar planets around very low mass stars," says Nicholas Law, an astronomer at UT and the principal investigator for the Dunlap Institute Telescope. The onset of the continuous polar night in early October will allow the telescope to take observations 24 hours a day for 6 months at a stretch. That should make it about 10 times easier for astronomers to detect extrasolar planets transiting across the face of their parent star than at observatories at lower latitudes, Law says.
The 0.5-meter telescope may be just the beginning. Canadian astronomers have been talking informally about the possibility of a 2-meter-class Canadian Arctic Telescope. And the site "certainly could eventually work for a 4-meter or even larger telescopes," Law says. Such telescopes would be used to monitor star-spot activity, spot supernovae, and for optical follow-up observations of gamma-ray bursts. Antarctica will still offer the best view onto the heart of our galaxy, but the Canadian High Arctic would give full access to key "fields" surveyed by NASA's Kepler and Hubble space telescopes. For astronomers, perhaps it's time to drive north.