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Nearby Universe Mapped in 3 Dimensions.
A new map developed by an international team of Astronomers should help you find your way around the universe - at least to a distance of 600 million light years. This new 3-dimensional map plots out the locations of all the major superclusters of Galaxies and the voids that surround them. It was developed using data from the 2MASS Redshift Survey, which calculated the redshifts (and therefore the distances) of 25,000 Galaxies across the entire sky.
A team of American, Australian and British Astronomers has released maps from the largest full-sky, three-dimensional survey of Galaxies ever conducted.
Their detailed maps show the 'local’ Cosmos out to a distance of 600 million light years, identifying 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% of the apparent mass of the Universe.
Within this vast volume, the most massive Galaxy supercluster is 400 million light years away. It was named after its identifier, the American Astronomer Harlow Shapley. The Shapley supercluster is so big that it takes light at least 20 million years to travel from its one end to the other. However, Shapley is not the only massive supercluster in our vicinity.
The Great Attractor supercluster, which is three times closer than Shapley, plays a bigger role in the motion of our Galaxy. According to the team, our Milky Way galaxy, its sister Galaxy Andromeda and other neighbouring Galaxies are moving towards the Great Attractor at an amazing speed of about a million miles per hour. The researchers also established that the Great Attractor is indeed an isolated supercluster and is not part of Shapley.
The new maps are based on the observation that, as the universe expands, the colours of Galaxies change as their emitted light waves are stretched or "redshifted". By measuring the extent of this redshift, Astronomers are able to calculate approximate distances to galaxies.
The new survey, known as the 2 mass 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. These redshifts were either measured specifically for the 2MRS or they were obtained from an even deeper survey of the southern sky, the 6dF Galaxy Redshift Survey (6dFGS).
The great advantage of 2MASS is that it detects light in the near-infrared, at wavelengths slightly longer than the visible light. The near-infrared waves are one of the few types of radiation that can penetrate gases and dust and that can be detected on the Earth’s surface. Although the 2MRS does not probe as deeply into space as other recent narrow-angle surveys, it covers the entire sky.
Galaxy Redshift surveys are 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’.
In order to map the Dark matter probed by the survey, the team used a novel technique borrowed from image processing. The method was partly developed by Prof. Ofer Lahav, a co-author of the paper and head of the Astrophysics group at University College London. The technique utilizes the relationship between Galaxy velocities and the total distribution of mass.
Original Source: BNSC News Release
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