A Mysterious Void Is Pushing The Milky Way
A massive void outside our extragalactic neighborhood could be pushing the Milky Way galaxy around the universe, according to a new study. The massive region, known as the dipole repellar, seems to be playing the role of a repellent that is aiding the movement of our Local Group of galaxies at a speed of about 2 million km/h.
According to the study published in Nature Astronomy, an international team of researchers observed the bizarre velocities of galaxies neighboring the Milky Way and combined them after studying their properties. Consequently, the research team could work out the movements of the Local Group of galaxies and understand the reason behind the observed flow.
Incidentally, scientists have previously already suggested the existence of the dipole repellar and also predicted that it works in tandem with another force in the universe called the Shapley attractor to move the galaxy around. However, the dipole repellar or void, which is a massive region largely empty of galaxies, is a bit of a mystery because it is difficult to observe due to the absence of light emitted from it.
The Shapley attractor, on the other hand, is an area where a high concentration of galaxies is present, and the region also generates a gravitational tug on the Milky Way. However, the Shapley attractor cannot alone influence the movement of the galaxies observed, according to the scientists.
The scientists found that the galaxies are being propelled away from the dipole repellar nearly as much as they are being pulled towards the Shapley attractor. Furthermore, the dipole repellar and Shapley attractor dominate the galaxy's trajectory around the universe.
"It was suggested a decade ago that an underdensity in the northern hemisphere roughly 15,000 km/s away contributes significantly to the observed flow," the research team of astronomers noted, according to Yahoo. The team added, "We show here that repulsion from an under-density is important and that the dominant influences causing the observed flow are a single attractor -- associated with the Shapley concentration -- and a single previously unidentified repellar, which contribute roughly equally to the cosmic microwave background dipole."
The researchers also mentioned that the repulsion source is identified for the first time. Furthermore, the study enabled the astronomers to find about the dual dominance of the dipole repellar and the Shapley attractor.