DECam: Gazing deep into the final frontier in search of dark energy
The National Optical Astronomy Observatory (NOAO) puts it into perspective right away: "Eight billion years ago, rays of light from distant galaxies began their long journey to Earth." It's important to hold that fact in mind, as we marvel at the first images from deep in the belly of our universe to arrive from the Chile-based Dark Energy Camera (DECam). As that name might suggest, peering at remote galaxies for purely visual gratification isn't the camera's primary purpose. The result of eight years of planning and hard work, involving engineers and scientists from three continents, the DECam is mounted on the Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile. Sitting atop a 7,200-foot mountain, the camera is part of the Dark Energy Survey, which intends to gather information on over 300 million galaxies. The goal is to better understand dark energy -- a concept that represents our best explanation for why the universe's rate of expansion is speeding up, rather than slowing due to gravity. Gaze past the break for the background on the project.
How does one gather light so dim that it's about one million times less intense than the faintest star that can be seen with the human eye? For starters, you'll need a 570-megapixel camera, with 74 CCDs built specifically to be sensitive to "redshifted" light (a term used to describe the effect the expansion of the universe has on light waves reaching our planet). All those megapixels peep a 2.2-degree field of view. That may not sound like much, but it equates to a single image snapping a section of sky approximately 20 times larger than the area the moon appears to cover. On top of that, you'll need a total of five lenses, the largest of which is one meter in diameter. The result? A camera that creates images one gigabyte in size each.
In total, 400 such pictures will be taken a night and then sent to the National Center for Supercomputing Applications (of Blue Waters fame) to be stored and compiled. The camera should be able to gather enough data to allow all four possible avenues for exploring dark energy: galaxy clusters, supernovae, large-scale galaxy clumping and weak gravitational lensing, at the same time. This marks the first time exploring all four is possible in a single experiment.
The first batch of these -- literally historic -- images shows us a tantalizing look at the Fornax cluster of galaxies, some 60 million light years from Earth. We even get to see a (relative) close-up of a "barred spiral galaxy" (above) called NGC 1365. This set of images is barely the beginning, though, with the camera not set to begin active operations until December. In the meantime? DES Project Director Josh Frieman told Engadget "Over the next two months, astronomers on the mountain will be testing the Dark Energy Camera and tuning the system that comprises the telescope plus the camera. The focus will not be on capturing images of interesting galaxies or other objects, that will come later this year."
Following that, over the next five years, it will endeavor to create a lucid astronomic image of a section measuring an eighth of the total sky. DECam won't just help us gain a better understanding of dark energy, either. It'll also be available for the greater astronomical community thanks to NOAO's open-access telescope allocation, which could see it tasked with everything from snapping asteroids closer to home, or helping to better understand the origins of the universe. And we thought our holiday snaps were precious.
[Image credit: Fermilab]
