Astronomers look back 13.8 billion years to create the largest ever map of the universe

The red dots are quasars, rings of glowing matter and energy with black holes at their centers, and the nearby galaxies are shown as yellow dots.

Sloan Digital Sky Survey (SDSS) have created the best known map of the large scale structure of the universe, based on the positions of quasars. Quasars are glowing rings of matter and energy around supermassive black holes, and are incredibly bright. This allows scientists to use them as markers, as the brightness of the quasars allow them to be clearly observed even from incredible distances.

Ashley Ross of the Ohio State University, the co-leader of the study said "Because quasars are so bright, we can see them all the way across the Universe. That makes them the ideal objects to use to make the biggest map yet." Gongbo Zhao from the National Astronomical Observatories of Chinese Academy of Sciences, the other co-leader of the study said, "These quasars are so far away that their light left them when the Universe was between three and seven billion years old, long before the Earth even existed."

 Astronomers look back 13.8 billion years to create the largest ever map of the universe

Image: Anand Raichoor/ SDSS

On the left of the map is the Earth, and towards the right, the map goes backwards in time. At the very edge of the map is the cosmic background radiation, a light signature from the big bang. The red dots are the quasars, and the nearby galaxies are shown as yellow dots. The black band between the quasars and the cosmic background radiation is from a period of the history of the universe known as the "dark ages". This was a time before the formation of most galaxies, stars and star systems.

In 2013, the European Space Agency and NASA collaborated on the Planck mission had created the then largest map of the Universe. The Planck mission observed the cosmic microwave background with the greatest precision, and mapped the temperature changes that showed the density of matter distributed across the universe. These clumps of matter were the seeds to the structures we observe today, and lead to the formation of galactic clusters, galaxies and star systems.

The map of the universe by the Planck mission.

The map of the universe by the Planck mission.

In 2016, the hundreds of scientists from the SDSS collaborated to make the largest 3D map of the universe. Individual galaxies were measured over a decade, and even then only a quarter of the sky was mapped in three dimensions. The map allowed scientists to measure the impact of dark energy on universal expansion. Rita Tojeiro of the University of St. Andrews had explained the map, "we see a dramatic connection between the sound wave imprints seen in the cosmic microwave background 400,000 years after the Big Bang to the clustering of galaxies 7-12 billion years later. The ability to observe a single well-modeled physical effect from recombination until today is a great boon for cosmology."


Daniel Eisenstein, SDS III

Each dot on the map is a galaxy at least 6 billion years into the past. The yellow galaxies are closer to the Earth, while the purple galaxies are the farthest. The map was created using the Baryon Oscillation Spectroscopic Survey (BOSS). The Extended Baryon Oscillation Spectroscopic Survey (eBoss) was used to find the accurate three dimensional positions of 147,00o quasars, which allowed for the creation of the best known large scale map of the universe.

The map measures conditions of the universe more than two billion years before the Earth was even formed. The findings conform to the standard model of cosmology, as well as Einstein's General Theory of Relativity. The eBOSS campaign continues, and astronomers will go on to add more galaxies and quasars to the map. The map will keep growing as these observations are made. Next generation sky surveys, including the Euclid satellite and the Dark Energy Spectroscopic Instrument (DESI) mission will contribute to the effort. The next generation of sky surveys are expected to increase the precision of the map by a factor of ten.

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