Scientists pin source of three mysterious signals coming from centre of Milky Way to...

For years, scientists have been puzzled by three mysterious signals coming from the centre of the Milky Way, a chaotic and violent place where Sagittarius A*, a supermassive black hole, sits. A study has now found that they could be the result of "excited dark matter". The centre of our galaxy has been releasing sudden spikes in energy which deep–space telescopes, such as the European Space Agency's INTEGRAL mission, can detect. However, dark matter itself has never been directly observed. It is believed to form a quarter of our universe, but scientists have never found any proof. This hypothetical form of matter is believed to surround the galaxies but does not interact with light or electromagnetic forces, making detection impossible. Researchers of a new paper published in The Astrophysical Journal Letters say that the three signals coming from the centre of our galaxy are the result of a type of dark matter.

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Milky Way's chaotic centre

Lead author Dr Shyam Balaji, of King's College London, says that regular cosmic events, such as stellar explosions, do not explain the "specific energy and shape observed coming from the centre of the Milky Way." But now, the "one excited dark matter model could account for at least two – possibly even three – of these kinds of unexplained signals at once." The vicious forces at work at the centre of the Milky Way trigger violent events where huge clouds of gas are crushed into stars. Besides, Sagittarius A* creates an extremely intense gravitational force. All these together release radiation that space telescopes have picked up. But not everything can be explained.

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Mysterious 511–keV emission line

One specific occurrence is a sharp spike in gamma–ray radiation at an extremely specific wavelength - the 511–keV emission line. Normal matter does not lead to something like this. The paper solves this mystery, theorising that "excited dark matter" is to blame. Harvard University describes it as an event that happens when dark matter particles collide and reach a higher-energy state before falling back to a lower energy state. This process releases energy in pairs of electrons and its anti-matter, a positron. Telescopes that sit outside Earth's radiation belts, like INTEGRAL, located at an altitude of 60,000 km, can detect this energy spike.

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Comparing this data to a model of how positrons might move through space showed the researchers that this exact phenomenon could lead to a spike in gamma–ray radiation, just like the mysterious 511–keV emission line they had observed. They think that excited dark matter can also explain other signals. Scientists think that a very high–energy light coming from the centre of the galaxy, known as the 2 MeV gamma–ray continuum, could also be originating from excited dark matter.