The Milky Way moves at roughly 391 miles per second, a speed largely attributed to the influence of a solitary gravitational source. However, new research is beginning to ask if this might not just be the case. What if instead of a single force, there were two?
A group of researchers have discovered that the speed of the Local Group (a cluster of galaxies that the Milky Way is a part of) is being driven by two primary sources. One we know as the Shapley Supercluster. But this newly found force is a bit different. How? Well, it’s a repeller now dubbed the Dipole Repeller.
This force was originally founded about a decade ago and, originally, it was suggested that it was likely to be a major contributing factor to the Local Group’s movements. However, at the time, it was too difficult to confirm this since these spaces are difficult to map due to the fact that they put out barely any light.
The researchers came to this conclusion by plotting the motion of many galaxies in a 3-D model, utilizing data from the Cosmicflows-2 database. Much of what they discovered was expected – many of the galaxies had a clear path to the Shapley Supercluster. But, even more interesting, they also shared almost the same point of origin – the Dipole Repeller. If you want to visualize this, imagine the Supercluster as the positive side of the magnet and the Dipole Repller as the negative end. The galaxies caught in the middle travel on charges that are driven from the positive end to the negative end, and vice versa.
Okay, up until this point it just sounds like basic science…right? Well, wrong - Because gravity doesn’t play by those rules! Since gravity is the dominant force acting on the galaxy….and gravity can’t repel, how is there a repllent?
It’s surmised that the Dipole Repeller is a big ball of nothing – literally.
It is likely a void with much less mass than the surrounding area. Because of this, it seems to act like a repeller because nearby space has a thicker concentration of matter. This then creates a gravitational gradient between the two points.
The above image is from Flickr user andy, and is Licensed under Creative Commons 2.0.