Dwarf galaxies found orbiting the Milky Way and Andromeda galaxy defies today's model of galaxy formation.
The galaxies have not been able to be incorporated into current galaxy-formation models, a Rochester Institute of Technology news release reported.
According to today's beliefs on galaxy formation, mysterious dark matter shapes 23 percent of the universe's mass.
"The model predicts that dwarf galaxies should form inside of small clumps of dark matter and that these clumps should be distributed randomly about their parent galaxy. "But what is observed is very different. The dwarf galaxies belonging to the Milky Way and Andromeda are seen to be orbiting in huge, thin disk-like structures," David Merritt, professor of astrophysics at Rochester Institute of Technology said in the news release.
A research team looked at earlier analyses that used the same data but came up with a lower probability that these structures would be found in the Milky Way and Andromeda galaxies.
"The earlier papers found structures in the simulations that no one would say really looked very much like the observed planar structures," Merritt said.
"Either the selection of model satellites is different from that of the observed ones, or an incomplete set of observational constraints has been considered, or the observed satellite distribution is inconsistent with basic assumptions. Once these issues have been addressed, the conclusions are different: Features like the observed planar structures are very rare," he said.
The standard cosmological model has been a staple for generations of scientists, but many are starting to question its accuracy.
"Our conclusion tends to favor an alternate, and much older, model: that the satellites were pulled out from another galaxy when it interacted with the Local Group galaxies in the distant past," Merrit said. "This 'tidal' model can naturally explain why the observed satellites are orbiting in thin disks."
