A team of researchers from the California Institute of Technology has detected what may be the most distant galaxy ever discovered, according to a release from the institution.
Publishing their findings in Astrophysical Journal Letters, Adi Zitrin, a NASA Hubble Postdoctoral Scholar in Astronomy, and Richard Ellis, a professor of astrophysics at University College London (and who was formerly a professor at Caltech for 15 years) presented evidence of a galaxy called EGS8p7 that is over 13.2 billion years old.
Earlier this year, NASA made EGS8p7 a candidate for further investigation based on data gathered by the Hubble and Spitzer telescopes. They used the multi-object spectrometer for infrared exploration (MOSFIRE) at the W.M. Keck Observatory in Hawaii to perform a spectrographic analysis of the galaxy to determine its redshift—how the galaxy’s light changes based on its movement in space.
Redshift is difficult to determine when studying the most distant objects in the universe, due to the way light behaved in the universe’s first half-billion years. As the first galaxies “turned on”, some of their light would have been muffled by clouds of neutral hydrogen atoms—eventually, however, those hydrogen atoms were reionized by the ultraviolet emissions that they previously filtered out. EGS8p7 is so old, however, that theoretically, the researchers should not have been able to observe a Lyman-alpha line from the galaxy.
“If you look at the galaxies in the early universe, there is a lot of neutral hydrogen that is not transparent to this emission,” said Zitrin. “We expect that most of the radiation from this galaxy would be absorbed by the hydrogen in the intervening space. Yet still we see Lyman-alpha from this galaxy.”
“The surprising aspect about the present discovery is that we have detected this Lyman-alpha line in an apparently faint galaxy at a redshift of 8.68, corresponding to a time when the universe should be full of absorbing hydrogen clouds,” Ellis added.
Other possibilities
Of course, other evidence offers a possible explanation.
“Evidence from several observations indicate that the reionization process probably is patchy,” Zitrin said. “Some objects are so bright that they form a bubble of ionized hydrogen. But the process is not coherent in all directions.”
“The galaxy we have observed, EGS8p7, which is unusually luminous, may be powered by a population of unusually hot stars, and it may have special properties that enabled it to create a large bubble of ionized hydrogen much earlier than is possible for more typical galaxies at these times,” adds Caltech graduate student Sirio Belli.
Zitrin notes that these findings may change how we look at the timeline of reionization in the early universe’s hydrogen clouds.
“We are currently calculating more thoroughly the exact chances of finding this galaxy and seeing this emission from it, and to understand whether we need to revise the timeline of the reionization, which is one of the major key questions to answer in our understanding of the evolution of the universe.”
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Image credit: I. Labbé (Leiden University), NASA/ESA/JPL-Caltech/Eurekalert
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