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Did Old Galaxies Grow Up Quicker Than New Ones?

This image shows the Hubble Ultra Deep Field 2012, an improved version of the Hubble Ultra Deep Field image featuring additional observation time. The new data have revealed for the first time a population of distant galaxies at redshifts between 9 and 12, including the most distant object observed to date. These galaxies will require confirmation using spectroscopy by the forthcoming NASA/ESA/CSA James Webb Space Telescope before they are considered to be fully confirmed.

The space between the galaxies is expanding. Credit: NASA/HST

Did some of the oldest galaxies grow up quickly? That’s an intriguing possibility raised by a research team that found “mature” galaxies some 12 billion light years away, when the universe was less than 2 billion years old.

“Today the universe is old and filled with galaxies that have largely stopped forming stars, a sign of galactic maturity,” stated Caroline Straatman from the Netherlands’ Leiden University, a graduate student who led the research. “However, in the distant past, galaxies were still actively growing by consuming gas and turning it into stars. This means that mature galaxies are expected to be almost non-existent when the universe was still young.”

Using data from the Magellan Baade Telescope’s FourStar Galaxy Evolution Survey and combining with other observatories, researchers looked at the young universe using near infrared wavelengths and found 15 galaxies at an average of 12 billion light-years away. While the galaxies are faint using visual wavelengths, they were easy to spot in infrared — and hosted as many as 100 billion stars per galaxy, on average.

The Milky Way over the ESO 3.6-metre Telescope, a photo submitted via Your ESO Pictures Flickr Group.  Credit:  ESO/A. Santerne

The Milky Way over the ESO 3.6-metre Telescope, a photo submitted via Your ESO Pictures Flickr Group. Credit: ESO/A. Santerne

These galaxies each have a similar mass to the Milky Way, but stopped making stars when the universe was “only 12 percent of its current age”, researchers said. This implies that star-forming happened much more quickly in the past than right now, since the rate is estimated at several hundred times higher than what is observed in the Milky Way now.

It’s not clear what caused the rapid aging, but you can be sure researchers will look into this further. You can read the research in Astrophysical Journal Letters or in preprint version on Arxiv. Other databases used include Hubble’s Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and the Great Observatories Origins Deep Survey.

Source: Netherlands Research School for Astronomy

About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

Comments on this entry are closed.

  • Michael March 14, 2014, 2:04 PM

    Wouldn’t a simpler explaination be that the universe is older than 13.7 billion years. We’ll learn more and see further back in time once the Webb and the other ‘next’ generation of telescopes come online.

  • john kulick March 16, 2014, 10:04 AM

    If the effect of gravity varied over the passage of Cosmological Time (as believed by Dirac and Gamow), then it would be expected to see stars evolve much more quickly in the past.

    (I have a paper to be published soon which espouses such a model)

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