For a long time, astronomers and physicists were sure about one thing: The expansion of the universe was slowing down—an insight based on Albert Einstein’s theory of General Relativity.
They were wrong. In the '90s, thanks to the Hubble Telescope, scientists discovered that the universe has actually been speeding up since the Big Bang. And more than 10 years after that revelation, they still don’t know why. The most popular explanation focuses on a mysterious, exotic substance, dark energy, that possesses unusual gravitational properties. It could make up as much as 73% of the universe’s energy-matter—compared to stars and planets, which make up a measly 5%.
On September 17th, an international team of 120 scientists unveiled a new tool, 10 years in the making, that may shed light on dark energy: the 570-megapixel Dark Energy Camera. It is the world’s most powerful digital camera, capable of recording light from galaxies 8 billion light years away.
Built in Illinois by the Department of Energy’s Fermi National Accelerator Laboratory (or Fermilab), the camera was installed on a hilltop observatory in the Chilean Andes, where atmospheric conditions are ideal. On September 12th, the camera recorded its first images—of a few galaxy clusters that lie 60 million light years from Earth. "Some of these galaxies are so distant that the light we see from them will have left the galaxy when the universe was less than half its current age," say the scientists.
So what, exactly, will images of galaxies tell us about the history of the universe? The camera is part of a massive international effort to explain the universe’s acceleration, called the Dark Energy Survey. The group will be studying four types of phenomena: galaxy clusters, supernovae, the large-scale clumping of galaxies, and weak gravitational lensing. Each of those have been studied on their own, but for the first time, scientists will be able to cross-reference each type of element against the others, rendering a more precise understanding of their behaviors. "Comparison of results … could reveal that our understanding of gravity must be overhauled," the Survey explains on its website.
What’s really wild about the Dark Energy Survey (and the eponymous camera) is that it could lead to a revision of Einstein’s ideas about gravity. "Most experts believe that nothing short of a revolution in our understanding of fundamental physics will be required to achieve a full understanding of the cosmic acceleration," say the scientists. Over the next 525 nights of observation, the camera will capture a detailed 3-D map of about 1/8th of the sky (that’s over 300 million galaxies). But we may hear about their early discoveries as soon as next year. "The results of this survey will bring us closer to understanding the mystery of dark energy," added James Siegrist, associate director at the U.S. Department of Energy. "And what it means for the universe."
Find out more about the Dark Energy Survey here.