The Press Stories
Experts have found that two-thirds of the known universe is made up of ‘dark energy’ and only 31 percent is made up of matter – most of which is made up of ‘dark matter’.
Astronomers at the University of California at Riverside have used a variety of tools and a new ‘galaxy orbit’ technique to determine how much matter exists in the universe.
To calculate this, they first looked at how orbiting neighboring galaxies in a galaxy and then measured the entire universe.
The team found that 31 percent of the universe is matter, and the rest is made up of dark energy – a form of ‘unknown energy’ that scientists still do not understand.
At 31 percent, the majority – 80 percent – is made up of dark matter, an object found only by its gravitational interactions with other things.
Researchers say this is ‘one of the most accurate measurements ever made using the Galaxy Cluster technique’.
Astronomers at the University of California at Riverside have found that 69 percent of the universe is dark energy, 31 percent matter, and 80 percent dark matter.
Globally, researchers say the amount of known matter is very small – just 20 percent of gas, dust, stars, galaxies and planets.
If all things in the universe were spread out evenly in space – it would have ‘density equal to six hydrogen atoms per cubic meter’.
“However, we know that 80 percent of the matter is really dark, and in fact, most of it does not contain hydrogen atoms, but rather a type of substance that cosmologists do not yet understand,” said lead writer Mohammed Abdullah.
Determining how much matter exists in the universe is not an easy task, cosmologists have explained, relying on both observations and simulations.
As part of their measurement, the team compared their results with other predictions and computer simulations and found the ‘Goldilocks’ image to be ‘correct’.
To estimate matter in a cluster, the team calculated the statistics for one galaxy based on the way they orbited others, and then measured the entire cluster.
Combining galaxy clusters and comparing these calculations with simulations of an object expected in the universe gave the team the most accurate figure ever recorded.
‘We have succeeded in creating one of the most accurate measurements ever made using the Galaxy Cluster technique,’ said co-author Gillian Wilson.
This is the first application of the galaxy orbit technique – the size of an object in a galaxy is determined by looking at how it orbits other galaxies.
‘A higher percentage of material will cause more clusters,’ Abdullah said.
Hubble’s image shows a galaxy cluster – researchers used information from such galaxies to calculate the total mass of a known universe
Like Goldilocks, the team compares the number of galaxy clusters they have measured with predictions of numerical simulations to determine which answer is ‘correct’.
“The ‘Goldilocks’ challenge for our team is to measure the number of clusters and determine which answer is” correct, “Abdullah said.
‘But it is difficult to accurately measure the mass of any galaxy cluster because most things are so dark that telescopes cannot see it.’
The dark matter is a relatively unknown substance that is thought to be the gravitational ‘glue’ that holds the galaxies together.
Calculations show that many galaxies will rupture instead of rotate if they are not joined together by a large amount of dark matter.
Unfortunately, this is never seen directly and can only be seen by its interaction with other types of objects by gravity.
To overcome this difficulty, astronomers have developed a cosmological instrument called the Calvite, which measures the mass of a galaxy cluster using the orbits of its member galaxies.
The researchers then used a publicly available list of Galaxy clusters to create the ‘Call W Gate 19’ for observations from the Sloan Digital Sky Survey (SDSS).
Finally, they compared the number of clusters in their new list with simulations to determine the size of the total object in the universe.
“One great advantage of using our Calvit Galaxy orbit technique is that our team was able to determine a mass for each cluster individually, rather than relying on indirect, statistical methods,” said third co-author Anatoly Clipin.
By combining their measurements from other teams that used different techniques, they were able to determine a better integrated value.
The findings have been published Journal of Astronomy.
