Photo: Andromeda Galaxy
The mass of the Milky Way Galaxy could be much less than has been believed up to now, according to a study published in the Monthly Notices of the Royal Astronomical Society.
According to research performed by experts at the University of Edinburgh, the Milky Way’s mass is around 50 percent of Andromeda, the closest galaxy that is not a satellite of our own.
Both the Milky Way and Andromeda are spiral galaxies and they are the largest galaxies within what astronomers call the Local Group consisting of at least a dozen, mostly rather small, galaxies.
Nevertheless, according to the study, Andromeda has a greater mass than the Milky Way because it contains a large amount of “dark matter,” an invisible substance that is thought to provide enough mass - and therefore gravity - to keep spiral galaxies from flying apart as they rotate.
According to the scientists who produced the study, Andromeda could contain double the dark matter of the Milky Way, despite the fact that both galaxies are roughly the same diameter in terms of their visible size.
Earlier studies were only able to measure the mass in the interior regions of the galaxies, but this latest project has managed to include the invisible mass in the outer regions.
“We always suspected that Andromeda is more massive than the Milky Way, but weighting both galaxies simultaneously proved to be extremely challenging,” the team leader, Dr. Jorge Penarrubia, said.