Dark energy: Can $40m camera help solve its mystery? (+video)
The Dark Energy Camera, on a telescope high in the Chilean desert, is expected to capture 300 million galaxies, 100,000 galaxy clusters, and some 4,000 supernovae over the next five years.
Using a cosmic looking glass that would dazzle Sherlock Holmes, an international team of astronomers has taken the first major step in a five-year observing project to help crack a case you could call The Sign of Dark Energy.Skip to next paragraph
In Pictures Looking into the skies: Telescopes
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The team has released the first stunning images from a $40 million camera that over the next five years is expected to capture and help characterize 300 million galaxies, 100,000 galaxy clusters, and some 4,000 exploding stars, or supernovae – all in the quest to figure out the nature of dark energy and how it has affected the evolution of the cosmos.
Where gravity exerts a pull on other objects in space, dark energy pushes objects apart, causing the universe to expand at an increasing rate.
The name dark energy was coined shortly after the phenomenon was discovered – in no small part to convey its mysterious nature.
Some theorists posit that dark energy is the cosmological constant first proposed, then withdrawn, by Albert Einstein. Einstein invoked it as he worked out the implications of his theory of general relativity for the evolution of the universe. His equations pointed to the eventual collapse of the universe under its own gravity, but the universe at the time was widely thought to be static. So he added a cosmological constant to his calculations to keep the universe from collapse.
A cosmological constant would permeate the universe in ways that would induce it to expand at an increasing rate.
Others have proposed that dark energy varies with time and may even be a fifth fundamental force of nature, dubbed quintessence. Since it varies, it could be a repulsive force or one that attracts, depending on other conditions in the universe.
Whatever the explanation, "we believe dark energy became the dominant force driving the large-scale evolution of the universe several billion years ago," says Joshua Frieman, a researcher at the Fermi National Accelerator Laboratory in Batavia, Ill., and the director of the Dark Energy Survey project. "So we want to go back somewhat farther than that to see whether the properties of dark energy have changed over time – since that would give us clues to its nature."
The Dark Energy Camera, bolted to the back end of a 4-meter telescope high in the Chilean desert, aims to hunt for dark energy through its influence on some of the universe's largest visible structures, peering back through time to a period when the universe was roughly 5 billion years old. During its five-year run, the camera will survey about 1/8th of the sky.
The discovery of dark energy is a classic case of scientists pursuing one objective stumbling on something profound in the process.
Two teams of scientists working independently first reported the discovery of dark energy’s effect in 1998 and 1999. The research teams had aimed to measure the expansion rate of the cosmos at different periods in its history.
To do that, they hunted for light from a particular type of exploding star as a tool to help them clock the rate at which the universe is expanding following the Big Bang, a sudden release of energy that spawned the visible universe some 13.8 billion years ago.
The species of supernovae the teams hunted, so-called type 1a supernovae, reach the same peak intrinsic brightness wherever they explode. For a time, a supernova's light can outshine the light from its host galaxy. Because light dims at a known rate as it travels, measurements or estimates of peak brightness of a supernova's light when it reaches Earth can reveal the distances to the galaxy hosting the explosion.