Galactic Old Timers

hs-2012-48a-670Astronomers have uncovered seven primitive galaxies that formed more than 13 billion years ago, when the universe was less than 4 percent of its present age. The deepest images to date from the Hubble Space Telescope show the first statistically significant sample that gives us an idea of how abundant galaxies were in the era when they were first forming.

The newly discovered galaxies are seen as they looked 380 to 600 million years after the big bang. Astronomers study the distant universe in near-infrared light because the expansion of space stretches ultraviolet and visible light from galaxies into infrared wavelengths, a phenomenon called redshift. The farther away a galaxy, the greater its redshift. One of these galaxies may be a distance record breaker, observed 380 million years after the big bang, corresponding to a redshift of 11.9.

The hot stars in the first galaxies provided radiation to warm the cold hydrogen that formed soon after the big bang. That made the universe transparent to light, allowing us to look far back into time. The galaxies in the new study are seen in this early epoch. Data shows that this was a gradual process, occurring over several hundred million years, with galaxies slowly building up their stars and chemical elements.

Image Credit: NASA

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