A new, Very Large Telescope (VLT) has been used to survey distant galaxies with surprising results. “Astronomers always knew they were missing some fraction of the galaxies,” explains Matthew Hayes, the lead author of the research team’s findings, “but for the first time we now have a measurement. The number of missed galaxies is substantial.” The math reveals that the universe is 90% larger than originally thought.
Traditionally, faint “fingerprints” of light emitted by hydrogen known as the Lyman-alpha line have been used to probe galaxies in the distant universe. This light, though, becomes trapped within the galaxy emitting it, since most of these photons are destroyed as they interact with interstellar gas and dust clouds. These surveys using Lyman-alpha were therefore only able to see a fraction of the light being produced. With new methods and state-of-the-art cameras alongside the VLT, astronomers incorporated into the survey of these galaxies an additional light traveling at a different wavelength (also emitted by hydrogen) known as the H-alpha line. At a different wavelength, H-alpha light is seemingly unaffected by the Interstellar Medium in comparison with the Lyman-alpha light, uncovering of some of the faintest galaxies formed in the early life of the Universe. Team member Goran Ostlin commented, “This is the first time we have observed a patch of the sky so deeply in light coming from hydrogen at these two very specific wavelengths, and this proved crucial.”
The results of these new surveys have made it clear to cosmologists, who’ve increasingly depended on the Lyman-alpha light to examine the early history of the Universe, just how substantial the number of missed galaxies was in the past. Co-author Miguel Mas-Hesse says, “Now that we know how much light we’ve been missing, we can start to create far more accurate representations of the cosmos, understanding better how quickly stars have formed at different times in the life of the Universe.”
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