Dead Galaxies in a Young Universe? What Webb Just Revealed

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If we think of the early universe, we often visualize a time not long after the Big Bang. This time in the universe was highly energetic and stars were bursting into existence, with galaxies coming together in gas and dust clouds. But what if some of those galaxies have already gone extinct? The James Webb Space Telescope (JWST) may have found evidence that suggests that some of these galaxies, have ceased star formation just a billion years into the life of the universe! For astronomers, that’s equivalent of a toddler who’s already retired!

What happens when a galaxy dies?

A galaxy is considered “dead” or quenched if it stops producing new stars. Galaxies need cold hydrogen gas to generate stars, and once the gas runs out, the galaxy slowly fades as its existing stars die. Our understanding up to now, is that this process usually takes billions of years, and that galaxies create stars for a very long time before slowly dying out. So, this new idea of a galaxy dying just a few hundred million years after the Big Bang is a big deal.

What did JWST actually find?

A recent study based on observations from JWST showed a galaxy that had already stopped star formation just 700 million years after the Big Bang, which happened around 13.1 billion years ago. Astronomers have approximated that this galaxy formed stars in a short burst, forming lots of stars in only 30 to 90 million years, before stopping completely (Reuters, 2024). But this was not the only instance, as JWSR has found other galaxies that also show evidence of similarly early “quenching,” making scientists rethink the rate at which galaxies can expand and fizzle out.

James Webb Space Telescope fired its onboard thrusters for nearly five minutes (297 seconds) to complete the final post launch course correction to Webb?s trajectory. This mid-course correction burn inserted Webb toward its final orbit around the second Sun-Earth Lagrange point, or L2, nearly 1.5 million kilometres away from Earth.

Why is this such a big deal?

Prior to JWST, the oldest known quenched galaxies were billions of years old, but Webb’s infrared telescope lets us look farther back in time than ever before, and what it’s observing isn’t what our models predict.

Possible explanations for this include:

Rapid gas exhaustion: The galaxy used up its star forming fuel too quickly.
Black hole activity: A massive central black hole may have heated or dispersed the gas.
Environmental effects: Other nearby galaxies or some other cosmic phenomenon may have stripped away the gas.

Whatever the reason, the fact that this occurred so early is a surprise. As Harvard-Smithsonian Center for Astrophysics astronomer Tobias Looser summed up, “This is not what we thought the early universe looked like” (ScienceDaily, 2024).

What Does This Mean for Cosmology?

This discovery adds another puzzle piece to the image of how galaxies evolved. If galaxies do live fast and die young, we may be compelled to re-evaluate our assumptions about:

Galaxy formation: how and when it happens
What fuels and shuts down supernovae
Black holes and dark matter halos’ influence

What is a supernova? Credit: Coffeekai / Getty Images

The JWST is still just getting started. With more data coming in every day, we can expect to learn much more about the early universe in the months and years ahead.

These early “dead” galaxies may be rare cosmic oddities or they might be more common than we ever imagined. Either way, they’re forcing us to think differently about how galaxies live, evolve, and die and in doing so, they’re breathing new life into the science of the cosmos.

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