The James Webb Space Telescope’s JADES survey recently observed a galaxy that shouldn’t be visible, because it existed only 300 million years after the Big Bang.
At that point in cosmic history, the universe was shrouded by neutral hydrogen, and most objects and phenomena would not be visible until nearly a billion years later.
For now, researchers think the light might be coming from the first stars to exist, or outflows from a supermassive black hole at the galactic core. But the source remains unknown.
Deep in the universe are stars and galaxies and objects so distant that the light we’re watching them produce is billions of years old. But there is one ancient light we can see that we shouldn’t be seeing at all.
As part of the James Webb Space Telescope Advanced Deep Extragalactic Survey (JADES), NASA’s James Webb Space Telescope (JWST) spotted something that should not be visible to us—the galaxy JADES-GS-z13-1. This galaxy existed only 330 million years after the Big Bang, which was very much still the universe’s baby phase.
Webb was able to spot GS-z13-1 in the first place by picking up on clear Lyman-alpha emissions from the galaxy. These emissions are released when an electron in a neutral hydrogen atom is excited by a photon that is energetic enough, and are very commonly detected throughout the cosmos. But here’s the thing—they’re very commonly detected now. Technically speaking, we should not be able to detect Lyman-alpha emissions from just 330 million years after the Big Bang.
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Shrouded in neutral hydrogen, which absorbs light, the universe was mostly opaque during its earliest days, and remained so until about a billion years after its birth. It was only during the epoch of reionization that light from stars became powerful enough to tear apart these atoms, rip off their electrons, and escape through the cloud. With all that neutral hydrogen now ionized—meaning that it was positively charged, as a result of losing its negatively charged electrons—the universe became transparent. That’s the first moment at which we should be able to detect Lyman-alpha emissions.
But if this didn’t happen until about a billion years after the Big Bang, how is it possible that scientists can see GS-z13-1, which existed when its light should have been obscured?
“The unexpected Lyman-alpha emission indicates the galaxy is a prolific producer and leaker of ionizing photons,” NASA and ESA researchers said in a study recently published in the journal Nature. “This suggests massive, hot stars or an active galactic nucleus (AGN) have created an early reionized region to prevent complete [suppression] of Lyman-alpha.”
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It is possible that the first stars to exist—known as Population III or Pop III stars—are the source of the light coming from GS-z13-1. These stars are thought to have been much more massive and luminous than stars that exist now, and it would be an incredible discovery if it was confirmed that the Lyman-alpha emissions are coming from Pop III stars. But there are some issues with this theory—the stellar mass predicted from the galaxy is not high enough to allow for these stars, for example. There are also some other emissions expected from Pop III stars that are missing from GS-z13-1.
The researchers think another possibility is the supermassive black hole in the galaxy’s active galactic nucleus, or AGN. Supermassive black holes accrete and devour so much matter that they belch out enormous and extremely bright outflows of gas, which scientists think could have been enough to reionize just one section of the universe a little bit early.
For now, we’re all still in the dark. But scientists are grateful for—if confused by the existence of—this ancient flashlight.
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Elizabeth Rayne is a creature who writes. Her work has appeared in Popular Mechanics, Ars Technica, SYFY WIRE, Space.com, Live Science, Den of Geek, Forbidden Futures and Collective Tales. She lurks right outside New York City with her parrot, Lestat. When not writing, she can be found drawing, playing the piano or shapeshifting.