The maps show the “local” cosmos out to a distance of 600 million light years, and identify all the major superclusters of galaxies and voids. They also provide important clues regarding the distribution of the mysterious "dark matter" and "dark energy" which are thought to account for up to 96 percent of the apparent mass of the Universe.
The maps show the “local” cosmos out to a distance of 600 million light years, and identify all the major superclusters of galaxies and voids. They also provide important clues regarding the distribution of the mysterious "dark matter" and "dark energy" which are thought to account for up to 96 percent of the apparent mass of the Universe.
This massive matter includes the Shapley supercluster, which is 400 million light years away and so big that it takes light at least 20 million years to travel from its one end to the other. The other galaxy within this matter is the Great Attractor supercluster, which is three times closer to us than Shapley and plays a bigger role in the motion of our Galaxy, the Milky Way.
The team said the Milky Way galaxy and its sister, the Andromeda Galaxy along with other neighbouring galaxies were moving towards the Great Attractor at an amazing speed of about a million miles per hour.
The new maps were based on observations, which showed that as the Universe expanded the colours of galaxies changed as their emitted light waves got stretched or “redshifted”.
By measuring the extent of this redshift, it is possible for astronomers to calculate approximate distances to galaxies, said Dr. Pirin Erdogdu from Nottingham University and lead author of the paper, adding that Galaxy redshift surveys were however, only able to detect luminous matter.
“This luminous matter accounts for no more than a small fraction of the total matter in the Universe. The remainder is composed of a mysterious substance called dark matter and an even more elusive component named "dark energy". We need to map the distribution of dark matter rather than luminous matter in order to understand large-scale motions in our Universe,” he said.
“Fortunately on large scales, dark matter is distributed almost the same way as luminous matter, so we can use one to help unravel the other,” he added.
Their new survey, known as the 2MASS Redshift Survey (2MRS), has combined two dimensional positions and colours from the Two Micron All Sky Survey (2MASS), with redshifts of 25,000 galaxies over most of the sky.
Her collaborator, Dr. Thomas Jarrett from Caltech, added, “the other advantage of observing in the near-infrared wavelength is the fact that it traces directly the luminous matter, and thus the dark matter, as well”.
”Our nearly two decade effort has produced the absolute best ever map of the nearby Universe. With this we hope to elucidate the nature and disposition of dark matter and understand much, much more about our cosmological model and about galaxies themselves,” added Prof. John Huchra of Harvard University.
”It is like reconstructing the true street map of London just from a satellite image of London taken at night. The street lights, like the luminous galaxies, act as beacons of the underlying roads,” Prof. Ofer Lahav, co-author of the paper and head of the astrophysics group at University College London, further said.
The findings are presented in the paper “Reconstructed Density and Velocity Fields from the 2MASS Redshift Survey", and are set to appear in the Monthly Notices of the Royal Astronomical Society.
Bureau Report
