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Distant galaxy helped tidy up early universe, scientists say

Using data from space telescopes, scientists say they have located a galaxy formed more than 13 billion years ago when the universe was young and still permeated with a fog of hydrogen gas.

By / September 19, 2012

In the big image at left, the many galaxies of a massive cluster called MACS J1149+2223 dominate the scene. Gravitational lensing by the giant cluster brightened the light from the newfound galaxy, known as MACS 1149-JD, some 15 times. At upper right, a partial zoom-in shows MACS 1149-JD in more detail, and a deeper zoom appears to the lower right.

NASA/ESA/STScI/JHU

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A hunt for galaxies that brought the toddler universe out of its dark ages has bagged what may be the most distant specimen yet discovered, a galaxy seen as it was more than 13 billion years ago when it was just 200 million years old.

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The galaxy, which was found using data from the Hubble and Spitzer Space Telescopes, is seen when the universe was only 500 million years old. A munchkin by today's standards, the galaxy’s mass was 200 million times the mass of the sun, compared with 700 billion solar masses for the Milky Way or 10 billion solar masses for the Milky Way's smaller companion, the Large Magellanic Cloud.

But the newly discovered galaxy's age – and the preponderance of hot, massive stars it hosted – place it among a category of objects that researchers say helped convert a fog of neutral hydrogen gas permeating the ancient universe into the transparent cosmos we see today.

The process, known as re-ionization, is thought to have started around 400 million years after the Big Bang, a sudden release of an enormous amount of energy that cosmologists have tagged as the birth of the universe.

Over the next 600 million years, stars and galaxies formed and the universe continued to expand. Radiation from the first generations of stars – and particularly from emissions stemming from the actions of super-massive black holes at the hearts of the rising number of growing galaxies – ionized the intergalactic hydrogen, in effect lifting the fog.

Relics of this period, 13-billion-year-old stars, populate the halo of the Milky Way, notes Wei Zheng, an astronomer at the Johns Hopkins University in Baltimore and the lead author of a formal report of the discovery, which is being published in Thursday’s issue of the journal Nature.

In a sense, the galaxy he and his colleagues have uncovered opens a window on the infant stages of our own galaxy.

"This is just like being an archaeologist" hunting for evidence of early civilizations, Dr. Zheng says. "You know it must be there. It's exciting to see the real pieces."

The ability to study these galaxies and their role in the universe's evolution is expected to take a big leap forward when NASA launches the James Webb Space Telescope, currently slated for lift-off sometime in 2018.

The team's report is not the first claiming evidence for galaxies during this crucial time in the evolution of the universe. Over the past eight years, a few groups using ground- and space-based telescopes have reported detections of infant galaxies at comparable distances – some 13 billion to 13.3 billion light-years away.

But uncertainties in the analysis of these previous detections are large, researchers say, owing to the faintness of the objects and to the limited amount of data researchers could gather on telltale signs in the galaxies' light that help estimate distance.

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