Is this the first glimpse of dark matter?

If you stand back from our galaxy in your mind's eye, you might picture the Milky Way as a bright disc wrapped in silence.

But researchers now say there is a faint glow in that silence, and it may carry the first direct hint of the most elusive substance in the universe. It is a small clue for now, but it has set the scientific world abuzz.

For nearly a century, dark matter has sat at the centre of one of astronomy's great mysteries. Scientists proposed that an invisible material surrounds galaxies and holds them together. They believed it shapes the vast cosmic web that spans the universe. But they have never seen it. They have only watched its gravitational pull on stars and galaxies, and wondered what could lie behind it.

A new study by Professor Tomonori Totani of the University of Tokyo suggests that the answer might finally be coming into view.

Totani examined 15 years of data from Nasa's Fermi Gamma-ray Space Telescope. He noticed a pattern of gamma rays rising from the Milky Way's halo.

The shape of this glow appeared to match the expected outline of dark matter that spreads out from the galactic centre.

His analysis points to a possible signal from hypothetical particles known as weakly interacting massive particles. These particles, often called wimps, are a leading candidate for dark matter. They rarely meet or collide, but if they do, they can annihilate each other and release high-energy gamma rays. Totani believes the glow fits this picture.

However, many astronomers remain cautious to call it a day. They note that other astrophysical processes may explain the light. They also point out the absence of similar signals from dwarf galaxies. Several researchers say the modeling must be tested further.