KMSP - Hundreds of scientists from around the world have assembled the largest ever three-dimensional map of the universe that contains 1.2 million galaxies. It’s a project ultimately devoted to understanding why the universe is continuously expanding and where the mysterious force called dark matter fits into it.
“We have spent a decade collecting measurements of 1.2 million galaxies over one quarter of the sky to map out the structure of the Universe over a volume of 650 cubic billion light years,” says Jeremy Tinker of New York University, a co-leader of the scientific team that led this effort. “This map has allowed us to make the best measurements yet of the effects of dark energy in the expansion of the Universe.”
The full image covers roughly a 20th of the sky with every dot indicating the position of a galaxy, 1.2 million in all, covering 6 billion light years in width, 4.5 billion light years high, and 500 million light years thick. Their color indicates their distance from Earth ranging from yellow as the closest to purple as the farthest.
The crazy part is the image above only represents about 3% of the full survey, or 48,741 galaxies. Even more astonishing is how much further these scientists have to go to take a picture of every galaxy thought to be in existence. Many scientists estimate that number to be well over one hundred billion.
But scientists can learn plenty without having to map out the entire universe. Using a system called BOSS (Baryon Oscillation Spectroscopic Survey), they are able to estimate the size of pressure waves that formed early in the universe called Baryonic Acoustic Oscillations. This helps them study the expansion of the universe in a way never thought possible, by using dark matter.
Dark matter is thought to counteract gravity which is why so many scientists believe that the universe is expanding rather than contracting, a theory which has never been proven. But this new image, and likely many more to come, could get scientists infinitely closer to answering that question, and hopefully dozens more along the way.
Image credit: Daniel Eisenstein and the SDSS-III collaboration
HOW THE 2D IMAGE ABOVE IS MAPPED IN 3D…
The rectangle on the far left shows a cutout of 1000 sq. degrees in the sky containing nearly 120,000 galaxies, or roughly 10% of the total survey. The spectroscopic measurements of each galaxy — every dot in that cutout — transform the two-dimensional picture into a three-dimensional map, extending our view out to 7 billion years in the past. The brighter regions in this map correspond to the regions of the Universe with more galaxies and therefore more dark matter. The extra matter in those regions creates an excess gravitational pull, which makes the map a test of Einstein’s theory of gravity.
Image credit: Jeremy Tinker and the SDSS-III collaboration