clipped from: space.newscientist.com Enormous sound waves seen rippling through a galaxy cluster are heating up its gas, new observations suggest. This may solve a longstanding puzzle about why such clusters refuse to cool down.
Astronomers discovered in the 1970s that the vast reservoirs of gas located in galaxy clusters – massive groupings of hundreds or thousands of galaxies – glow brightly in x-rays. This suggested that the gas should be cooling and contracting as it radiates its energy away. But in 2001, new observations failed to find the expected pools of cool gas, puzzling astronomers.
