Scientists believe they've spotted the biggest wave ever discovered. But before you pull out your surfboard, you should probably know this is a tad bigger than anything you'd find on Earth: this wave is roiling through an extremely hot gas cloud in the Perseus cluster and stretches 200,000 light-years across, meaning it's twice the size of the Milky Way galaxy.
The classic image of a wave – the rounded, curling shape as it crashes over itself – is actually called a Kelvin-Helmholtz wave, and it's created when two fluids moving at different speeds brush past each other. The wind blowing across the surface of the water is the most obvious example, but they can also be seen in cloud formations and in the sun's corona.
Using data gathered by NASA's Chandra X-ray Observatory and computer simulations, a team of researchers found what they believe is the largest such wave ever identified. It shows up in X-ray images as a "bay"-shaped feature in the extremely hot gas cloud surrounding the galaxies in the Perseus cluster.
Computer simulations suggest that billions of years ago that gas was fairly settled, but a close encounter with a smaller, passing galaxy cluster threw it off balance, churning the gas into an expanding spiral. Over the span of several billion years, this gas would have spread about 500,000 light-years away from the center of the cluster, creating massive waves that could spend a few hundred million years rolling around the edges before fading away.
"Perseus is one of the most massive nearby clusters and the brightest one in X-rays, so Chandra data provide us with unparalleled detail," says Stephen Walker, lead author of the study. "The wave we've identified is associated with the flyby of a smaller cluster, which shows that the merger activity that produced these giant structures is still ongoing."
The research could help astronomers better understand how these gigantic structures formed and interact with each other.
The study was published in the Monthly Notices of the Royal Astronomical Society, and a mesmerizing video showing the formation of the wave can be seen below.