A team of scientists have demonstrated how to “weigh” galaxy clusters using light from the earliest moments of the universe—a new method that could help shed light on dark matter, dark energy and other mysteries of the cosmos, such as how the universe formed.
The new method calculates the bending of light around galaxy clusters using the orientation of light from shortly after the Big Bang—data taken by the South Pole Telescope and the Dark Energy Camera.
“Gravitational lensing,” a phenomenon in which light distorts as it’s affected by the gravity of big objects like galaxies, can function as a kind of magnifying glass. It’s helped scientists discover key information about the universe—but it’s always been done by looking for the smearing of light around distant objects like stars.
In a study published in Physical Review Letters, Fermilab and University of Chicago scientist Brad Benson and colleagues use a different method to calculate the masses of distant galaxies: the polarization, or orientation, of the light left over from the moments after the Big Bang.
“Making this estimate is important because most of the mass of galaxy clusters isn’t even visible—it’s dark matter, which does not emit light but interacts through gravity and makes up about 85% of the matter in our universe,” said Benson, an assistant professor in the Department of Astronomy and Astrophysics. “Since photons from the cosmic microwave background have literally traveled across the entire observable universe, this method has the potential to more accurately measure the dark matter mass in the most distant galaxy clusters.”