The Hebrew University of Jerusalem researchers claim that they have found why the Milky Way is moving with respect to the universe’s expansion at 2 million km/h or 630 km per second. According to them, the repelling force comes from an unknown region.
“By 3-d mapping the flow of galaxies through space, we found that our Milky Way galaxy is speeding away from a large, previously unidentified region of low density. Because it repels rather than attracts, we call this region the Dipole Repeller,” explained Prof. Yehuda Hoffman, researcher of the study to be published in the forthcoming issue of Nature Astronomy, Science Daily reports. “In addition to being pulled towards the known Shapley Concentration, we are also being pushed away from the newly discovered Dipole Repeller. Thus it has become apparent that push and pull are of comparable importance at our location.”
The idea of a low-density region has actually been proposed before, the researchers say in a media release. However, proving its existence has been difficult, they argue.
Together with other researchers in the USA and France, the research team used telescopes, including the Hubble Space Telescope. They created a 3-dimensional map of the galaxy flow field, which are responses to the distribution of matter away from regions that are empty and toward regions with mass concentration.
The researchers have also studied the peculiar velocities of other galaxies around our own galaxy. After analyzing these data as well as their statistical analysis of their properties, the researchers determined an underlying mass distribution that is composed of luminous galaxies and dark matter.
After identifying the Dipole Repeller, the research team has determined our galaxy’s motion, direction, and magnitude. However, further research is still necessary and they expect that upgraded equipments in the future will be able to determine what galaxies reside in this area.