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It might make up more than 80 per cent of the known universe, but as of yet scientists have still not managed to directly observe one of the universe's greatest mysteries - dark matter.

In recent months there have been detections from the sun and in orbit around Earth, but now scientists think they have found it in neighbouring galaxies.

They spotted photon emissions coming from space - and one of the best possible explanations is that they came from particles of dark matter.

Research led by the Swiss Federal Institute of Technology in Lausanne has found particles in other galaxies that could be dark matter (illustrated). They analysed X-ray signals emitted by the Perseus galaxy cluster and the Andromeda galaxy. The signal could not be attributed to any regular form of matter

Two groups have recently announced that they have detected a signal that could be a sign of dark matter, with the research to be published next week in Physical Review Letters.

One of them, which included Lausanne-based Swiss Federal Institute of Technology scientists Dr Oleg Ruchayskiy and Dr Alexey Boyarsky, found it by analysing X-rays emitted by two celestial objects - the Perseus galaxy cluster and the Andromeda galaxy.

After having collected thousands of signals from the Esa's XMM-Newton telescope and eliminated all those coming from known particles and atoms, they detected an anomaly that, even considering the possibility of instrument or measurement error, caught their attention.

The signal appears in the X-ray spectrum as a weak, abnormal photon emission that could not be attributed to any known form of matter.

Above all, 'the signal's distribution within the galaxy corresponds exactly to what we were expecting with dark matter, that is, concentrated and intense in the centre of objects and weaker and diffuse on the edges,' explained Dr Ruchayskiy.

'With the goal of verifying our findings, we then looked at data from our own galaxy, the Milky Way, and made the same observations,' added Dr Boyarsky.

The discovery was made using Esa's XMM-Newton telescope (illustration shown). The researchers detected an anomaly that, even considering the possibility of instrument or measurement error, caught their attention - as it could be the best sign of dark matter yet

The signal comes from a very rare event in the universe: a photon emitted due to the destruction of a hypothetical particle, possibly a 'sterile neutrino'.

If the discovery is confirmed, it will open up new avenues of research in particle physics.

'It could usher in a new era in astronomy,' said Dr Ruchayskiy.

And Dr Boyarsky said: 'Confirmation of this discovery may lead to construction of new telescopes specially designed for studying the signals from dark matter particles.

'We will know where to look in order to trace dark structures in space and will be able to reconstruct how the universe has formed.' 

The research, to be published in Physical Review Letters, included EPFL scientists Dr Oleg Ruchayskiy and Dr Alexey Boyarsky. They found the signal by analysing X-rays emitted by two celestial objects - the Perseus galaxy cluster and the Andromeda galaxy (shown)