Our astronomers are part of an international team that has taken another step towards solving the puzzle of what dark matter might be made of.
Dark matter is believed to make up the majority of matter in the Universe and is different from the matter that people, planets and stars are made from.
No one knows what it is and physicists have debated if the mysterious substance exists as actual particles or as a result of deviations from the law of gravity.
The researchers measured the expected and actual gravity from distortions in the images of millions of galaxies located behind about 259,000 isolated galaxies that were closer to Earth.
They wanted to see how light from more distant galaxies had been warped by their gravity – a process called gravitational lensing.
The lensing they saw was stronger than the stars in the galaxies should produce, according to Albert Einstein’s famous theory of General Relativity.
This points to the potential existence of a large amount of invisible dark matter particles.
Although the astronomers found that the influence of dark matter was the most likely cause of the extra lensing, they added that an explanation in terms of a modified theory of gravity could not be definitively ruled out by their measurements.
Research co-author Dr Kyle Oman, in our Institute for Computational Cosmology, said the team’s observations pointed either to the presence of a lot of additional, invisible matter, “in which case we are seeing another manifestation of the dark matter phenomenon. Otherwise we need to modify or replace General Relativity as a theory of gravity”.