Look closely at the galaxies in the above photo. They look bizarre, don't they? These galaxies aren't just bizarre, they are 60 times brighter in the infrared spectrum than they are in the reddest colors that the Hubble Space Telescope can detect. In fact, these galaxies are so strange that they are actually a whole new morphological classification--the system used by scientists to class galaxies based on visual appearance--of galaxy.
Deep in the cosmos--nearly 13 billion light-years from Earth--lay galaxies that are so far into the red part of the spectrum that the most powerful visible-light telescope--the Hubble--can't even see them. These galaxies are so far into the infrared range that it took the Spitzer Space Telescope, a powerful infrared space observatory, to stumble upon them.
How Red Is Red?
The human eye can see electromagnetic waves in the spectral range that lie between 380 and 760nm (nanometers), in what's also known as the visible light range. The Hubble can "see" waves between 115 and 1030nm (from ultraviolet to the tip of the near-infrared spectrum), and the Spitzer can see from 3000 to 180,000nm (from mid-infrared through far-infrared and up to terahertz radiation on the edge of the microwave band).
The galaxies are actually so red in fact that the researchers "had to go to extremes to get the models to match our observations," according to Jiasheng Huang of the Harvard-Smithsonian Center for Astrophysics (CfA).
Plenty of Possibilities, But No Answers
According to the Harvard-Smithsonian Center for Astrophysics--a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory--the galaxies can be this red for a number of reasons. For starters, the galaxies may be simply so far away that a process called redshifting may cause them to appear red due to the expansion of the universe. That is, the galaxies may be moving away from Earth, which would cause the wavelengths of the light given off to become longer (and therefore more red).
Alternatively, the galaxies could be filled with old red giant stars that are near their deathbed, or the galaxies might be very dusty and obscuring the visual range waves from Hubble.
The researchers found four of these odd-looking galaxies close together (in the astronomical scheme of things, anyway), and they believe that there may be more of them. The researchers plan to use the Spitzer observatory to find more of these sorts of galaxies.
When more powerful instruments--like the Atacama Large Millimeter Array--are ready to use, astronomers plan to measure the redshift to determine if that's why they are so red. If it isn't just a case of redshift, then these galaxies will become an even greater mystery. "Hubble has shown us some of the first protogalaxies that formed, but nothing that looks like this," says co-author Giovanni Fazio of the CfA.
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