Planet Earth sits amidst the Milk Way Galaxy, an assembly of some 300 billion stars, with billions more planets spinning about them.
Just beyond the outskirts of the Milk Way lies its orbiting companion, the Andromeda Galaxy. Together they form the most significant pair in a small group of galaxies known as the Local Group.
The Local Group stretches some 3 million light years across, a distance that's near impossible for the human mind to fathom. But now, thanks to new research, scientists are thinking even bigger -- thus, the Local Sheet.
"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," explains Professor Marshall McCall, lead author of the study published today in the Monthly Notices of the Royal Astronomical Society. "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."
12 of the 14 giants in the Local Sheet's "council," including the Milky Way and Andromeda, are spiral galaxies, flattened, spinning disks of stars. The other two are more more vertically-expansive elliptical galaxies. These two sit on either end of the Local Sheet. McCall suggests winds expelled by these elliptical galaxies as they were birthed may have pushed masses of cosmic energy towards the Local Group, helping form Milky Way and Andromeda.
Scientists think this new understanding of the universe's geography can continue to help astronomers better ascertain the origins of the cosmos.
"Recent surveys of the more distant universe have revealed that galaxies lie in sheets and filaments with large regions of empty space called voids in between," says McCall. "The geometry is like that of a sponge. What the new map reveals is that structure akin to that seen on large scales extends down to the smallest."
[Monthly Notices of the Royal Astronomical Society]