Looking back to the cradle of our universe
The discovery comes from the Frontier Fields program, which is pushing the limits of how far back we can see into the distant universe using NASA's multi-wavelength suite of Great Observatories. Spitzer sees infrared light, Hubble sees visible and shorter-wavelength infrared light, and NASA's Chandra X-ray Observatory sees X-rays. The telescopes are getting a boost from natural lenses: they peer through clusters of galaxies, where gravity magnifies the light of more distant galaxies.
The Frontier Fields program will image six galaxy clusters in total. Hubble images of the region are used to spot candidate distant galaxies, and then Spitzer is needed to determine if the galaxies are, in fact, as far as they seem. Spitzer data also help determine how many stars are in the galaxy.
These early results from the program come from images of the Abell 2744 galaxy cluster. The distance to this galaxy, if confirmed, would make it one of the farthest known. Astronomers say it has a redshift of 8, which is a measure of the degree to which its light has been shifted to redder wavelengths due to the expansion of our universe. The farther a galaxy, the higher the redshift. The farthest confirmed galaxy has a redshift of more than 7. Other candidates have been identified with redshifts as high as 11.
"Just a handful of galaxies at these great distances are known," said Jason Surace, of NASA's Spitzer Science Center at the California Institute of Technology, Pasadena. "The Frontier Fields program is already working to find more of these distant, faint galaxies. This is a preview of what's to come."
The findings, led by astronomers from the Instituto de Astrofísica de Canarias and La Laguna University, are accepted for publication in the scientific journal Astronomy and Astrophysics Letters.
Probing the z>6 Universe with the first Hubble Frontier Fields cluster Abell 2744 H. Atek et al., arXiv1311.7670 arxiv.org/abs/1311.7670