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Current Affairs

Scientists determine total amount of matter in universe

Date: 30 September 2020 Tags: Space

Issue

 A team of scientists have precisely measured the total amount of matter present in the universe.

 

Background

A top goal in cosmology is to precisely measure the total amount of matter in the universe, a daunting exercise for even the most mathematically proficient.

 

Details

  • The team determined that matter makes up 31% of the total amount of matter and energy in the universe, with the remainder consisting of dark energy.

  • 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.

  • However, since we know 80% of matter is actually dark matter, in reality, most of this matter consists not of hydrogen atoms but rather of a type of matter which cosmologists have not yet understood.

  • 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.

  • Because present-day galaxy clusters have formed from matter that has collapsed over billions of years under its own gravity, the number of clusters observed at the present time is very sensitive to cosmological conditions and, in particular, the total amount of matter.

  • The team of astronomers first developed "GalWeight", a cosmological tool to measure the mass of a galaxy cluster using the orbits of its member galaxies.

  • Finally, they compared the number of clusters in their new catalog with simulations to determine the total amount of matter in the universe.

  • By combining their measurement with those from the other teams that used different techniques, the UCR-led team was able to determine a best combined value.