Galaxy Formation

New Clues About How Ancient Galaxies Lit up the Universe

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Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
calla.e.cofield@jpl.nasa.gov 

 

This deep-field view of the sky (center) taken by NASA’s Hubble and Spitzer space telescopes is dominated by galaxies – including some very faint, very distant ones – circled in red. The bottom right inset shows the light collected from one of those galaxies during a long-duration observation.Credit: NASA/JPL-Caltech/ESA/Spitzer/P. Oesch/S. De Barros/I.Labbe

 

NASA’s Spitzer Space Telescope has revealed that some of the universe’s earliest galaxies were brighter than expected. The excess light is a byproduct of the galaxies releasing incredibly high amounts of ionizing radiation. The finding offers clues to the cause of the Epoch of Reionization, a major cosmic event that transformed the universe from being mostly opaque to the brilliant starscape seen today. 

In a new study (Royal Astronomical Society), researchers report on observations of some of the first galaxies to form in the universe, less than 1 billion years after the big bang (or a little more than 13 billion years ago). The data show that in a few specific wavelengths of infrared light, the galaxies are considerably brighter than scientists anticipated. The study is the first to confirm this phenomenon for a large sampling of galaxies from this period, showing that these were not special cases of excessive brightness, but that even average galaxies present at that time were much brighter in these wavelengths than galaxies we see today. 

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