A recent study highlights the discovery of a new dwarf galaxy orbiting the Milky Way that is emitting a strong gamma ray signature, a strong sign of the possibility of dark matter at the center of the galaxy.
The study by Carnegie Mellon University academics has been submitted to the journal Physical Review Letters.
Statement from lead author
“Something in the direction of this dwarf galaxy is emitting gamma rays,” noted Alex Geringer-Sameth, a postdoctoral research associate in the physics department at Carnegie Mellon University and lead author. “There’s no conventional reason this galaxy should be giving off gamma rays, so it’s potentially a signal for dark matter.”
New dwarf galaxy named Reticulum 2
The new dwarf galaxy is called Reticulum 2, and was identified recently as a part of the Dark Energy Survey, research that maps the southern sky to analyze the expansion of the universe. A mere 98,000 light-years from Earth, Reticulum 2 is arguably the closest dwarf galaxy located to date.
Moreover, data from NASA’s Fermi Gamma-ray Space Telescope shows a great deal of gamma rays coming from the direction of the galaxy, significantly above normal background levels.
“In the search for dark matter, gamma rays from a dwarf galaxy have long been considered a very strong signature,” explains Savvas Koushiappas, assistant professor of physics at Brown University. “It seems like we may now be detecting such a thing for the first time.”
The researchers note, however, that this is still a preliminary study.
More on dark matter
Exactly what dark matter is, or if it really exists, remains a mystery, but current theories argue it represents close to 80% of all the matter in the universe. Astronomers and physicists believe dark matter exists because it creates gravitational effects on visible matter, and explains the observed rotation of galaxies and galaxy clusters as well as variations in cosmic microwaves
“The gravitational detection of dark matter tells you very little about the particle behavior of the dark matter,” says Matthew Walker, assistant professor of physics and a member of Carnegie Mellon’s McWilliams Center for Cosmology. “But now we may have a non-gravitational detection that shows dark matter behaving like a particle, which is a holy grail of sorts.”
One popular theory suggests that dark matter particles are WIMPs (Weakly Interacting Massive Particles). According to the theory, when pairs of WIMPs collide, they destroy each other, producing high-energy gamma rays.
That means there should be strong gamma rays coming from places where WIMPs are thought to be found in quantity, such as the dense central regions of galaxies. The problem is that he high-energy rays can be produced from many sources, including black holes and pulsars, which makes identifying WIMP interactions difficult.