“Strange Glow” –Neutron Stars or Dark Matter Source of Odd Light At Milky Way’s Center?

Milky Way Disk

 

A strange glow coming from the Milky Way’s center was thought to be due to a hidden population of pulsars. But a new look at older research shows that dark matter might still be responsible, perhaps making our galaxy unique.

“It’s like the glow of a metropolis at night where maps show only a town.” The unexplained gamma-ray glow coming from the Milky Way’s center has fueled a decade-old debate about what could be powering this excess of energetic light.

“There’s something happening in the data we don’t understand,” said Rebecca Leane, a theoretical physicist at the Massachusetts Institute of Technology and co-author of a new study that reveals a likely flaw in the suggestion that the glow was from large population of dim neutron stars.

An earlier, 2017 theory predicts how dark matter may be annihilating much more rapidly in the Milky Way, than in smaller or larger galaxies and the early Universe that would explain why the Milky Way appears to be special.

Dark Matter –“Emerged From an Eon Before the Big Bang” (Weekend Feature)

The new study, along with two others that came out in March, reports Charles Wood in Quanta, reopens the possibility that space-based instruments have found the first direct evidence of the elusive “dark matter” thought to pervade the universe.

The problem first appeared in 2009, when Dan Hooper, an astrophysicist at the University of Chicago, and Lisa Goodenough, then a graduate student at New York University, noticed that NASA’s Fermi Gamma-ray Space Telescope appeared to be picking up too many of the energetic photons known as gamma rays.

“Inexplicable” –The Strange Glow at Milky Way’s Center

“He suggested.” writes Wood in Dark Matter Gets a Reprieve in New Analysis, “the anomaly could originate from a theoretical jumbling throng of dark matter particles in the galaxy’s center. While dark matter doesn’t shine or fraternize with known particles, in the right sort of collision these particles could annihilate in a shower of familiar matter and antimatter that would then go out with a puff of gamma rays. A measurement of these offshoots would represent the first evidence of dark matter that wasn’t exclusively gravitational in nature.”

In 2017, The Galaxy reported that researchers at the Tata Institute of Fundamental Research proposed a theory that predicts how dark matter may be annihilating much more rapidly in the Milky Way, than in smaller or larger galaxies and the early Universe.

Anirban Das, with his colleague, Dr. Basudeb Dasgupta, pursued this possibility because almost all observations made so far indicate no signals of dark matter annihilation anywhere — except the tantalizing signals from the Milky Way seen by the PAMELA and AMS02 detector and the Fermi gamma ray telescope. If the dark matter origin of these signals stands further scrutiny and signals aren’t seen from anywhere except the Milky Way, their theory would explain why the Milky Way appears to be special.

Milky Way’s ‘Dark-Matter’ Anomaly –“Explains Why Our Galaxy Appears to be Special”

This study published in the journal Physical Review Letters on 23rd June 2017, shows that this peculiar behavior of the annihilation rate, in that it is not the same everywhere, stems from the symmetries of the annihilating dark matter particles.

Further, it would predict that dark matter is made of more than one particle and interacts through a yet-undiscovered low-mass particle. The absence of dark matter annihilation signals outside the Milky Way could be a crucial hint towards this richer theory of dark matter, which will be tested by future observations.

Image of Milky Way’s dark-matter disk is shown at top of page.

The Daily Galaxy via Quanta and Tata Institute of Fundamental Research

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