Russian Doll galaxy cluster to decode dark energy

​Washington: Using data from NASA’s Chandra X-ray Observatory and other optical telescopes, astronomers have developed a powerful new method for investigating dark energy - the mysterious energy that is currently driving the accelerating expansion of the universe.

The technique takes advantage of the observation that the outer reaches of galaxy clusters, the largest structures in the universe held together by gravity, show similarity in their X-ray emission profiles and sizes.

More massive clusters are simply scaled up versions of less massive ones. “In this sense, galaxy clusters are like 'Russian dolls', with smaller ones having a similar shape to the larger ones,” said Andrea Morandi from University of Alabama in Huntsville.

“Knowing this lets us compare them and accurately determine their distances across billions of light years,” he added. By using these galaxy clusters as distance markers, astronomers can measure how quickly the universe was expanding at different times since the Big Bang.

According to Einstein’s theory of general relativity, the rate of expansion is determined by the properties of dark energy plus the amount of matter in the Universe, where the latter is mostly made up of unseen material called dark matter.