Astronomers, working on a new study, have managed to map the location of the Milky Way Galaxy among a group of larger galaxies, offering greater insight into Earth's immediate neighborhood in the universe.
The Milky Way Galaxy is one of the dominant members -- the other one being the Andromeda galaxy -- of a small group of galaxies called the Local Group, which is a cluster of 54 galaxies that lies about three million light years across. However, according to researchers, much less was known about the Milky Way’s surroundings until a new study, led by Marshall McCall of York University in Canada, mapped out bright galaxies within 35 million light years of the Earth, providing “an extended picture of what lies beyond our doorstep.”
“All bright galaxies within 20 million light years, including us, are organized in a 'Local Sheet' 34-million light years across and only 1.5-million light years thick,” McCall said, in a statement. “The Milky Way and Andromeda are encircled by twelve large galaxies arranged in a ring about 24-million light years across – this 'Council of Giants' stands in gravitational judgment of the Local Group by restricting its range of influence.”
According to McCall, 12 of the 14 giant galaxies in the Local Sheet, which is a nearby region of the observable universe where the Milky Way, the members of the Local Group and other galaxies share a similar peculiar velocity, are “spiral galaxies” that have highly flattened disks in which stars are forming. The remaining two galaxies are more puffy “elliptical galaxies,” that sit on opposite sides of the Council.
Winds expelled by these elliptical galaxies in the earliest phases of their formation might have driven gases inward toward the Local Group, which could have helped in the formation of disks of the Milky Way and Andromeda galaxies, according to the study, published Tuesday in the journal Monthly Notices of the Royal Astronomical Society.
“Thinking of a galaxy as a screw in a piece of wood, the direction of spin can be described as the direction the screw would move (in or out) if it were turned the same way as the galaxy rotates,” McCall said. “Unexpectedly, the spin directions of Council giants are arranged around a small circle on the sky. This unusual alignment might have been set up by gravitational torques imposed by the Milky Way and Andromeda when the universe was smaller.”