updated 9/3/2010 12:27:16 PM ET 2010-09-03T16:27:16

Ancient galaxies may be cosmic senior citizens today, but some have a wild streak in their past, one packed with frenetic star birth, astronomers say.

Researchers using NASA's Spitzer Space Telescope have found that a significant set of galaxies in an ancient, distant cluster were actively forming stars about 10 billion years ago, which is how long it's taken for their light to reach Earth.

The star birthrate is also oddly higher in the cluster's center than at its edges — the opposite of what has been observed in our local part of the universe, where galactic clusters are full of massive elliptical galaxies packed with only old stars.

Missing link of galaxies?
The recent discovery, made by an international team of researchers led by Kim-Vy Tran of Texas A&M University, may ultimately reveal more about how such massive galaxies form.

Astronomers have long suspected that star formation likely peaked long, long ago, when the universe was just a few billion years old. But the new findings may help pinpoint the epoch when galaxy clusters were making the last of their stars. Armed with this information, astronomers could focus on understanding why massive assemblies of galaxies transition from very active to passive.

"Our study shows that by looking farther into the distant universe, we have revealed the missing link between the active galaxies and the quiescent behemoths that live in the local universe," Tran said in a statement.

Wild youths for old galaxies
Tran and her team spent four months analyzing images taken by Spitzer of a distant galaxy cluster known as CLG J02182-05102 about 10 billion light-years from Earth. The team determined that the galaxy cluster produces hundreds to thousands of new stars every year.

That's a far higher birth rate than what is seen in galaxies relatively nearby.

Exactly why the star-making power increases as galaxies become more crowded remains a mystery.

Tran suspects the densely populated surroundings could lead to galaxies triggering activity in one another, or that all galaxies were extremely active when the universe was young.

The fact that Tran's team was able to see these active galaxies so far back in time is only the preface to what they expect eventually to learn about these clusters. Tran will continue to lead an international collaboration to examine these clusters more thoroughly.

"We will analyze new observations scheduled to be taken with the Hubble Space Telescope and Herschel Space Telescope to study these galaxies more carefully to understand why they are so active," Tran said. "We will also start looking at several more distant galaxy clusters to see if we find similar behavior."

The research was detailed in the Aug. 20 issue of The Astrophysical Journal Letters.

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Photos: Month in space: August 2010

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  1. Colorful clash

    NASA's Great Observatories combine forces to create this beautiful image of two colliding galaxies. The Antennae galaxies, located about 62 million light-years from Earth, are shown in a composite view from the Chandra X-ray Observatory (blue for X-rays), the Hubble Space Telescope (gold and brown for optical wavelengths), and the Spitzer Space Telescope (red for infrared wavelengths). The readings were taken in 1999, 2003, 2004 and 2005 - then blended together for this Aug. 5 image. The fuller spectrum helps scientists understand the tidal forces shaping the Antennae. (Chandra X-ray Observatory Center) Back to slideshow navigation
  2. Wonders of Earth and sky

    In this long-exposure photo, a meteor streaks through the sky over a nature reserve in the southern Spanish town of Antequera early on Aug. 13. The Perseid meteor shower is sparked every August when Earth passes through a stream of space debris left by Comet Swift-Tuttle. (Jon Nazca / Reuters) Back to slideshow navigation
  3. Readying the Robonaut

    In the Space Station Processing Facility at NASA's Kennedy Space Center in Florida, the dexterous humanoid astronaut helper known as Robonaut 2, or R2, is secured to a base plate on Aug. 16. The plate is part of the robot's launch box, called SLEEPR, or Structural Launch Enclosure to Effectively Protect Robonaut. R2 will fly to the International Space Station aboard the space shuttle Discovery. Although it will initially only participate in operational tests, upgrades could eventually allow the robot to realize its true purpose -- helping spacewalking astronauts with tasks outside the space station. (Frankie Martin / NASA) Back to slideshow navigation
  4. Live fast, die young

    A spectacular new image from the European Southern Observatory’s Wide Field Imager at the La Silla Observatory in Chile, released July 28, shows the brilliant and unusual star WR 22 and its colorful surroundings. WR 22 is a very hot and bright star that is shedding its atmosphere into space at a rate many millions of times faster than the sun. It lies in the outer part of the dramatic Carina Nebula. (ESO) Back to slideshow navigation
  5. Ice on the loose

    The ice island that calved off Petermann Glacier in northwestern Greenland on Aug. 5 continues its slow migration down the fjord 11 days later. An imager on NASA’s Earth Observing-1 satellite captured this natural-color image on Aug. 16. (NASA) Back to slideshow navigation
  6. Tsunami on the sun

    Almost the full disk of the sun erupts in a tumult of activity on Aug. 1. This extreme ultraviolet image from NASA's Solar Dynamics Observatory shows a C3-class solar flare (the white area at upper left), a solar tsunami (the wavelike structure at upper right), multiple filaments of magnetism lifting off the stellar surface, large-scale shaking of the solar corona, radio bursts, a coronal mass ejection and more. Different colors in the image represent different gas temperatures. (AFP - Getty Images) Back to slideshow navigation
  7. All dressed up

    Russian cosmonaut Dmitri Kondratyev is assisted by specialists during a training session in a pool at the Star City space center outside Moscow on July 28. Kondratyev is scheduled to lift off for the International Space Station later this year. (Sergei Remezov / Reuters) Back to slideshow navigation
  8. A mudslide's mortal blow

    An image captured by DigitalGlobe's WorldView 2 satellite on Aug. 10 shows the devastation caused by a mudslide in Zhouqu, China. The catastrophe killed more than 1,200 people and left thousands more homeless. (DigitalGlobe) Back to slideshow navigation
  9. Land of the crescent

    The crescent moon is seen hanging in the sky over the mosques of old Cairo on Aug. 15, the fifth day of the Muslim holy month of Ramadan. (Asmaa Waguih / Reuters) Back to slideshow navigation
  10. Rovers ready to roll

    Two rover prototypes are prepared in Building 9 at NASA's Johnson Space Center in Texas on July 27 for the annual Desert RATS exploration exercise. The Desert Research and Technology Studies, planned this year in Arizona, are aimed at testing vehicles and instruments that could be used by astronauts on future missions to other worlds. (Regan Geeseman / NASA) Back to slideshow navigation
  11. Before and after the flood

    Two pictures from the Landsat 5 satellite illustrate the effects of flooding in Pakistan: The top image, captured Aug. 9, shows the region around the city of Khewali before the flood hit. The bottom image shows the same region on Aug. 12, after the flooding began. (AFP - Getty Images) Back to slideshow navigation
  12. Fixing the space station

    NASA spacewalker Tracy Caldwell Dyson works outside the International Space Station to replace a failed ammonia coolant pump module on Aug. 11. Despite some initial setbacks, the crucial repair operation was successful. (NASA TV via Reuters) Back to slideshow navigation
  13. Glorious galaxy

    A Hubble Space Telescope image, released Aug. 10, shows a majestic face-on spiral galaxy located deep within the Coma Cluster of galaxies, 320 million light-years away in the northern constellation Coma Berenices. The galaxy, known as NGC 4911, contains rich lanes of dust and gas near its center. These are silhouetted against glowing newborn star clusters and iridescent pink clouds of hydrogen - a telltale sign of star formation. (NASA) Back to slideshow navigation
  14. Great view

    NASA astronaut Doug Wheelock sent this picture of a section of Australia's Great Barrier Reef down to Earth from the International Space Station on Aug. 22. "I think even the great Impressionists would be awestruck with this natural display," Wheelock said. (Doug Wheelock / NASA) Back to slideshow navigation
  15. Ghostly mystery

    This image from the Hubble Space Telescope, obtained on Aug. 19, shows a ghostlike nebula known as IRAS 05437+2502. The nebula is a small star-forming region filled with dark dust that was first noted in images taken by the IRAS satellite in infrared light in 1983. The new image shows many new details, but it has not uncovered a clear cause of the bright sharp arc. (NASA/ESA/HUBBLE/JLP via AFP - Getty Images) Back to slideshow navigation
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