Astrophysicists Measure Total Amount of Matter in Universe | Astronomy - Sci-News.com

Using data on a sample of 756 galaxy clusters identified in the Sloan Digital Sky Survey (SDSS), a team of astrophysicists from the United States and Egypt has determined that matter makes up 31% of the total amount of matter and energy in the Universe, with the remainder consisting of dark energy.

“To put that amount of matter in context, if all the matter in the Universe were spread out evenly across space, it would correspond to an average mass density equal to only about six hydrogen atoms per cubic meter,” said study first author Mohamed Abdullah, a graduate student in the Department of Physics and Astronomy at the University of California Riverside and the Department of Astronomy at the Egypt’s National Research Institute of Astronomy and Geophysics.

One well-proven technique for determining the total amount of matter in the Universe is to compare the observed number and mass of galaxy clusters per unit volume with predictions from numerical simulations.

“But it is difficult to measure the mass of any galaxy cluster accurately because most of the matter is dark so we can’t see it with telescopes.”.

By combining their measurements with those from the other teams that used different techniques, they were able to determine a best combined value, concluding that matter makes up 31.5±1.3% of the total amount of matter and energy in the Universe.