Astronomers have mapped the large empty space near our Milky Way Galaxy
It also helps answer the question, ‘Why is there a difference in the speed of expansion of the universe and galaxies?’
Our universe is made up of a lot of empty space with little or no matter, also called a void. This is also expanding along with the expansion of the universe.
In space, galaxies feel gravitational pull from other objects nearby. A body with a larger mass exerts gravitational force on nearby celestial bodies. Because of these extra forces, the galaxies also move towards dense areas and away from regions with little mass, or voids.
Studying these phenomena, a team of astronomers has discovered more information about the vast empty cosmic structure surrounding our Milky Way galaxy. Astronomers calculated the distribution of mass responsible for this movement and created a three-dimensional map of our local Universe. This empty space that surrounds our Milky Way galaxy has been called the Local Void by astronomers.
Image: Shaded gray contours outline the extent of the Local Void, while blue dots show major mass constituents (large galaxies, galaxy groups, and clusters). The curved blue lines show the derived motions of these massive objects, after removing the overall expansion of the universe. The most important galaxy congregations are given special symbols, like the red ball identifying the Virgo Cluster. The dominant pattern of motions revealed by the orbits is a flow away from the Local Void.
Our Milky Way galaxy is close to a local void that lies at the edge of it. But this local void has not been studied much as it lies behind the centre of our galaxy, obscuring a direct view.
The team studied the motion of 18,000 galaxies and constructed a map. This map highlights the boundary of the void by observing the collection of matter and the absence of matter that defines the edge of the Local Void.
This technique was earlier used to identify a cluster of around one hundred thousand galaxies in 2014. The cluster was named Laniakea, meaning "immense heaven" in Hawaiian.
According to the astronomers, there is a deviation in the speed of expansion of the Milky Way, Andromeda, and other small neighbouring galaxies and the expansion of the universe. The reason behind this was not known for the last 30 years. The new study suggests that half of the deviation in speed is generated "locally" from the pull of nearby galaxies, in this case the Virgo Cluster.
The Milky Way is also responsible for the expansion of the local void. The galaxy is making it emptier.