Astronomers find strange new species of super-red galaxies

Astronomers have found what they’re calling a new “species” of ultra-red galaxy in the distant reaches of the universe, almost 13 billion light-years from Earth. The red galaxies were cloaked in dust and dimmed by the intervening distance. Even the Hubble Space Telescope couldn’t see it. NASA’s Spitzer Space Telescope – which is sensitive to infrared light – has now revealed not one, but four very red galaxies. And while astronomers can describe the members of this new “species,” they can’t explain what makes them so red in color.

Four newfound very red galaxies. Credit: David A. Aguilar (CfA)

Jiasheng Huang of the Harvard-Smithsonian Center for Astrophysics (CfA) is lead author of the paper announcing the find, published online by the Astrophysical Journal. He said:

We’ve had to go to extremes to get the models to match our observations.

Infrared light lies beyond the visible part of the electromagnetic spectrum. The newfound galaxies are more than 60 times brighter in the infrared than they are at the reddest colors the Hubble Space Telescope can detect. That’s why the Spitzer Space Telescope, which has been orbiting the sun since 2003, was able to see them.

Galaxies can be very red for several reasons. They might be very dusty. They might contain many old, red stars. Or they might be very distant, in which case the expansion of the universe stretches their light to longer wavelengths and hence redder colors (a process known as redshifting). All three reasons seem to apply to the newfound galaxies.

All four galaxies are grouped near each other and appear to be physically associated, rather than being a chance line-up. Due to their great distance, we see them as they were only a billion years after the Big Bang – an era when the first galaxies formed. Co-author Giovanni Fazio of the CfA said:

Hubble has shown us some of the first protogalaxies that formed, but nothing that looks like this. In a sense, these galaxies might be a ‘missing link’ in galactic evolution.

Next, researchers hope to measure an accurate redshift for the galaxies, which will require more powerful instruments like the Large Millimeter Telescope or Atacama Large Millimeter Array. They also plan to search for more examples of this new “species” of extremely red galaxies. Fazio said:

There’s evidence for others in other regions of the sky. We’ll analyze more Spitzer and Hubble observations to track them down.

Bottom line: Astronomers at the harvard-Smithsonian Center for Astrophysics (CfA) have discovered four examples of what they’re calling a new “species” of very red galaxy in the early universe.

Via the Harvard-Smithsonian Center for Astrophysics (CfA)

December 3, 2011

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