ASTRONOMERS are back in the dark about what dark matter might be, after new observations showed the mysterious substance may not be interacting with forces other than gravity after all.

Three years ago an international team of researchers led by Durham University thought they had made a breakthrough in ultimately identifying what dark matter is.

Observations using the Hubble Space Telescope appeared to show that a galaxy in the Abell 3827 cluster – approximately 1.3 billion light years from Earth – had become separated from the dark matter surrounding it. Such an offset is predicted during collisions if dark matter interacts with forces other than gravity, potentially providing clues about what the substance might be.

The chance orientation at which the Abell 3827 cluster is seen from Earth makes it possible to conduct highly sensitive measurements of its dark matter.

However, the same group of astronomers now say that new data from more recent observations shows that dark matter in the Abell 3827 cluster has not separated from its galaxy after all. The measurement is consistent with dark matter feeling only the force of gravity.

The latest findings are being presented at the European Week of Astronomy and Space Science meeting in Liverpool today. The research will be published in the journal Monthly Notices of the Royal Astronomical Society.

Lead author Dr Richard Massey, in the Centre for Extragalactic Astronomy at Durham University, said: “The search for dark matter is frustrating, but that’s science. When data improves, the conclusions can change. Meanwhile the hunt goes on for dark matter to reveal its nature.”

The Universe is composed of approximately 27 per cent dark matter with the remainder largely consisting of the equally mysterious dark energy. Normal matter, such as planets and stars, contributes a relatively small five per cent of the Universe.

To measure the dark matter in hundreds of galaxy clusters and continue the investigation, Durham University has just finished helping to build the new SuperBIT telescope, which rises above the Earth’s atmosphere under a giant helium balloon.

The research had been funded by the Royal Society and the Science and Technology Facilities Council in the UK and NASA.