A new astronomical camera designed to see through thick walls of galactic dust into the nurseries where stars are born is ready for astronomers to use.
The SCUBA-2 (Submillimetre Common User Bolometer Array) camera has now been successfully installed as part of the James Clerk Maxwell Telescope on Mauna Kea volcano in Hawaii, and recently completed testing and calibration, said Mark Halpern, a physics professor at the University of British Columbia who took part in the setup and testing.
Extremely cold detectors
SCUBA's camera relies on sensitive detectors that are cooled to just 0.1 degrees Kelvin – just slightly higher than absolute zero.
"Each and every little pixel is a superconductor," said Mark Halpern, a University of British Columbia physicist who helped develop the camera.
The extreme cold is needed because the superconducting material only exists in its useful form at that very low temperature. It also reduces the background signals caused by molecules bumping into each other, which increase with temperature.
"Temperature really just consists of things wiggling," Halpern said. "If you have a delicate thing, it's going to get bumped around by things at high temperatures."
The cold temperatures are obtained by applying a vacuum to liquid helium to reduce the pressure and therefore the temperature at which it boils. The temperature is extra cold when a lighter isotope of helium is used.
The camera is designed to be able to take pictures of areas within galaxies where newborn stars and their planets are forming. Stars form from clouds of dust and gas collapsing under the weight of their own gravity, and the thick dust absorbs all visible light. That makes it impossible to see inside the star nurseries using regular optical devices.
However, SCUBA-2 is able to see heat and other long wavelengths of light that are invisible to the human eye.
"It's really a lot like x-rays," Halpern said. Just as x-rays can see through human skin and clothes that are impenetrable to visible light, revealing bones and organs, SCUBA-2 can see right through the dust that obscures certain parts of galaxies.
"The galaxies are translucent at these wavelengths," Halpern said.
Objects such as stars and planets are visible because they are warmer than the surrounding universe, and SCUBA-2 can see the glow of the heat they give off.
One of the studies SCUBA-2 is undertaking is a survey of so-called "starburst galaxies," said Halpern, who is one of the coordinators for the international survey.
Such galaxies pop out 1000 new stars per year — a huge number compared to the one a year produced by our own galaxy, the Milky Way.
"They're unbelievably bright — no matter how far they are, we can see them," said Halpern. "They're like flashbulbs going off."
He added that neither the starburst galaxies' nor the Milky Way's rates of star formation are sustainable in the long term given the estimated age of the universe and the number of stars in each galaxy. By mapping star formation within galaxies, the study aims to help researchers understand how galaxies form and evolve over time.
SCUBA-2 is the faster, more powerful successor to a similar device called SCUBA.
According to Wayne Holland, a scientist from the UK Astronomy Technology Centre, which is leading the project, SCUBA-2 can image in a few hours an area of the sky that would have taken SCUBA 20 nights. In addition, its high sensitivity means it can detect faint objects that have never been seen before.
Canadians played a key role in the development of the camera. Halpern and colleagues at the University of British Columbia developed the electronics that read the signals from the detectors and the software used to analyze the data. Two accessories for the camera — a spectrometer and a polarizer — are currently being built in Lethbridge, Alta., and the University of Montreal, respectively. The University of Waterloo has been coordinating the Canadian contributions to the international project, which received part of its funding from the Canada Foundation for Innovation.