The anomalous gamma-ray signal coming from the core of the Milky Way Galaxy was first detected in 2009 by the Large Area Telescope, the primary instrument on NASA’s Fermi Gamma-ray Space Telescope.

“We had a working hypothesis that the signal was being emitted from thousands of rapidly spinning neutron stars called millisecond pulsars,” said Dr. Roland Crocker, an astrophysicist at the Research School of Astronomy and Astrophysics at Australian National University in Australia.

“At the distance to the center of our Milky Way Galaxy, the emission from many thousands of these whirling dense stars could be blending together to imitate the smoothly distributed signal we expect from dark matter.”

“Millisecond pulsars close to the Earth are known to be gamma-ray emitters,” he noted.

The findings, published in the journal Nature Astronomy, ruled out a provocative theory that dark matter, which is not well understood by scientists, was the origin of the signal.

There is broad scientific consensus that dark matter is widely present in the Universe and helps explain how galaxies hold together rather than fly apart as they spin.

“It is thought that dark matter is composed of Weakly Interacting Massive Particles, which would be expected to gather in the center of our Galaxy,” Dr. Crocker said.

“The theory is that, very occasionally, these particles crash into each other and radiate light a billion times more energetic than visible light.”

The Fermi telescope has given astronomers their clearest ever view of the gamma-ray sky in this energy range.

“While Milky Way’s center may be rich in dark matter, it is also populated by ancient stars that make up a structure called the Galactic bulge,” Dr. Crocker said.

The signal detected by Fermi closely traces the distribution of stars in the Galactic bulge.

“Ongoing observational and theoretical work is underway to verify or refute the hypothesis that the gamma-ray signal comes from millisecond pulsars,” the scientist said.

Source: Sci News