JWST has discovered that early galaxies also have unusual chemical features.
The impossibly early galaxies
As well as extremely lively early galaxies, JWST has also found extremely dead corpses: galaxies in the early universe that are relics of intense star formation at cosmic dawn.
Bright hydrogen gas is emitting light at enormous speeds, thousands of kilometers per second, characteristic of gas swirling around a supermassive black hole.
It has uncovered some extremely massive galaxies (as massive as our Milky Way today and more) that formed in the first 700 million years of cosmic history. Our current galaxy formation models can’t explain these objects—they are too big and formed too early.
They contain a significant amount of nitrogen, far more than what we observe in our sun, while most other metals are present in lower quantities. This suggests there were processes at play in the early universe we don’t yet fully understand.
But these are not your garden variety active galactic nuclei. For starters, they don’t emit any detectable X-rays, as is normally expected. Even more intriguingly, they seem to have the features of star populations.
JWST has yet to find this limit. However, it has uncovered many faint galaxies, far more than anticipated, emitting over four times the energetic photons (light particles) we expected.
These corpses had been found by Hubble and ground-based telescopes, but only JWST had the power to dissect their light to reveal how long they’ve been dead.
The discovery suggests these small galaxies may have played a crucial role in ending the cosmic “dark ages” not long after the Big Bang.
Cosmologists are still debating whether the models can be bent to fit (for example, maybe early star formation was extremely efficient) or whether we have to reconsider the nature of dark matter and how it gives rise to early collapsing objects.
This phenomenon, called an active galactic nucleus, usually indicates a feeding frenzy where a supermassive black hole is gobbling up all the gas around it, growing rapidly.
Initially, they were thought to be massive super-dense galaxies that shouldn’t be possible, but detailed observations in the past year have revealed a combination of deeply puzzling and contradictory properties.
When galaxies grow, their stars explode, creating dust. The bigger the galaxy, the more dust it has. This dust makes galaxies appear red because it absorbs the blue light. But here’s the catch: JWST has shown these first galaxies to be shockingly bright, massive and very blue, with no sign of any dust. That’s a real puzzle.
JWST will turn up many more of these objects in the next year and study the existing ones in greater detail. Either way, we will know soon.
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From dead galaxies to mysterious red dots, here’s what the James Webb Telescope has found in just 3 years (2024, December 28)
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There are many theories to explain the weird nature of these first galaxies. Do they have huge stars that just collapse due to gravity without undergoing massive supernova explosions?
We pushed further to find the point at which galaxies become so faint, they stop forming stars altogether. This helps us understand the conditions under which galaxy formation comes to an end.
It’s explored our own solar system, studied the atmospheres of distant planets in search of signs of life and probed the farthest depths to find the very first stars and galaxies formed in the universe.
