One moment *way* back in time

What did the universe look like 11 billion years ago? Something like this:

SDSS-II map slice.jpg

This image is part of the largest-ever 3-D map of the distant universe, which was released yesterday by scientists from the Sloan Digital Sky Survey III (SDSS-III) at the April meeting of the American Physical Society. Just a slice of the entire map, the image shows the distribution of intergalactic hydrogen gas: red areas have more gas, blue areas have less.

Scientists usually map the universe by looking at galaxies. But this study, which was led by Brookhaven cosmologist Anže Slosar, observed how light from quasars — among the brightest objects in the universe — is blocked as it passes through clouds of hydrogen gas.

As quasar light journeys toward Earth, it gets absorbed by hydrogen gas at specific wavelengths, depending upon the distance traveled. This results in an irregular pattern on the quasar light known as the “Lyman-alpha forest.” To get a full, 3-D map, the scientists, from SDSS-III’s Baryon Oscillation Spectroscopic Survey (BOSS) collaboration, analyzed 14,000 quasars.

3D map_2.jpg

A slice through the three-dimensional map of the universe. SDSS-III scientists are looking out from the Milky Way, at the bottom tip of the wedge. Distances are labeled on the right in billions of light-years. The black dots going out to about 7 billion light years are nearby galaxies. The red cross-hatched region could not be observed with the SDSS telescope, but the future BigBOSS survey, the proposed successor to BOSS, could observe it. The colored region shows the map of intergalactic hydrogen gas in the distant universe. Red areas have more gas; blue areas have less gas.

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