Universe's previously missing matter detected
Scientists have for the first time detected the missing matter in our universe – present in the form of strings of hot gas linking galaxies – that was unaccounted for by previous space observations. Apart from the mysterious and elusive dark matter – that is thought to permeate the majority of the universe – models of the universe predict that there should be about twice as much ordinary matter than what has been observed so far.
Researchers from Institute of Space Astrophysics in France and University of Edinburgh in the UK found the missing
matter – made of particles called baryons – linking galaxies together through filaments of hot, diffuse gas. “There is no instrument that we have invented yet that can directly observe this gas. It has been purely speculation until now,” said Richard Ellis at University College London.
The researchers instead took advantage of a phenomenon called the Sunyaev-Zel’dovich effect that occurs when light
left over from the big bang passes through hot gas, ‘New Scientist’ reported. As the light travels, some of it scatters off the electrons in the gas, leaving a dim patch in the cosmic microwave background – remnants from the birth of the cosmos.
In 2015, the Planck satellite created a map of this effect throughout the observable universe. Since the tendrils
of gas between galaxies are so diffuse, the dim blotches they cause are far too slight to be seen directly on Planck’s map. Researchers selected pairs of galaxies from the Sloan Digital Sky Survey that were expected to be connected by a strand of baryons.
They stacked the Planck signals for the areas between the galaxies, making the individually faint strands detectable en masse.