While it’s believed to make up 75 percent of the content of the universe, precious little is known about dark energy — the mysterious force believed to be governing the universe’s accelerating expansion. Now, a new 570-megapixel imaging device called the Dark Energy Camera, armed with an array of 74 CCD sensors, is being fired up for the first time, making Chile’s 1970s-era 4-meter Blanco telescope the world’s most powerful tool in the hunt for the elusive force.
Baryon acoustic oscillations are early sound waves frozen in place
The camera was funded and built by a 23-institution consortium called The Dark Energy Survey which will use it to study four phenomena. Type 1a supernovae are the closest thing astronomers have to a "standard candle" for measuring the distance to distant galaxies, and the team will measure some 3,000 of these exploding stars, comparing their distances with the stars’ redshift to calculate the rate of the universe’s expansion. Secondly, the team will study pressure waves called baryon acoustic oscillations (BAO) that pushed matter together in the years following the Big Bang. The effect is similar to the way sound waves temporarily increase the density of the air they pass through, only in the case of BAO, the lumps of matter remain frozen in place, and can provide insight into the history of the universe’s expansion. The team will also measure how the number of galaxy clusters has grown over time, and use an effect called gravitational lensing — whereby massive objects bend the light passing by — to make inferences about how "clumpy" the distribution of dark matter is in the universe.
The Dark Energy Survey isn’t alone in its hunt for dark energy — the WiggleZ Dark Energy Survey in Australia is another example — but it will be the largest galaxy survey of its kind. If you want to see what a 570-megapixel phone booth-sized imaging array can do for the night sky, the first images (below) from the Dark Energy Camera have been posted by Fermilab, and they don’t disappoint.