Researchers from The Australian National University (ANU) have found an
alternative explanation for a mysterious gamma-ray signal coming from the
center of the galaxy, which was long claimed as a signature of dark matter.
Gamma-rays are the form of electromagnetic radiation with the shortest
wavelength and highest energy.
Co-author of the study Associate Professor Roland Crocker said this
particular gamma-ray signal—known as the Galactic Center Excess—may actually
come from a specific type of rapidly-rotating neutron star, the super-dense
stellar remnants of some stars much more massive than our sun.
The Galactic Center Excess is an unexpected concentration of gamma-rays
emerging from the center of our galaxy that has long puzzled astronomers.
"Our work does not throw any doubt on the existence of the signal, but
offers another potential source," Associate Professor Crocker said.
"It is based on millisecond pulsars—neutron stars that spin really
quickly—around 100 times a second.
"Scientists have previously detected gamma-ray emissions from individual
millisecond pulsars in the neighborhood of the solar system, so we know
these objects emit gamma-rays. Our model demonstrates that the integrated
emission from a whole population of such stars, around 100,000 in number,
would produce a signal entirely compatible with the Galactic Center Excess."
The discovery may mean scientists have to re-think where they look for clues
about dark matter.
"The nature of dark matter is entirely unknown, so any potential clues
garner a lot of excitement," Associate Professor Crocker said.
"But our results point to another important source of gamma-ray production.
"For instance, the gamma-ray signal from Andromeda, the next closest large
galaxy to our own may be mostly due to millisecond pulsars."
ANU Masters student Anuj Gautam led the research, which also involved
scientists from The Australian Defense Force Academy, University of
Canterbury, and University of Tokyo.
The research has been published in Nature Astronomy.
Reference:
Roland Crocker, Millisecond pulsars from accretion-induced collapse as the
origin of the Galactic Centre gamma-ray excess signal, Nature Astronomy
(2022).
DOI: 10.1038/s41550-022-01658-3
Tags:
Space & Astrophysics