NASA’s James Webb Space Telescope is asking big questions about the early universe.
In its first images, JWST captured seemingly massive galaxies in the ancient universe. In fact, these galaxies appear to be too large to fit scientists’ current theories about how the universe grew. This has led some to worry that the history of the early universe needs to be rewritten.
But new observations of old Hubble Space Telescope data tell a different story. Maybe JWST isn’t as disruptive to cosmology as some scientists fear. Instead, the giant galaxies seen by JWST may have a simpler explanation.
Researchers shared these findings on February 9 Physical Review Letters.
Julian Muoz says JWST gives us a new language to understand the early universe. He is a cosmologist at the University of Texas at Austin. We should understand this language before we say, hey, we need to throw out everything we know in cosmology.
universe destroyer
Trouble began almost as soon as JWST took its first peek into the distant universe.
When this telescope looks at distant objects, it sees them as they appeared long ago. Why? Because light from such a distant object takes a long time to reach Earth. So when JWST peers into the farthest reaches of the universe, it sees things as they did shortly after the Big Bang.
The James Webb Telescope’s first observations of such a distant, ancient region of space is puzzling in two ways.
First, some of its images contain large numbers of galaxies. In fact, there is much more than astronomers have thought so far.
Second, some of these galaxies appear to be incredibly massive. These date back to the first 700 million years of the universe. They weighed 100 times what scientists thought they weighed at the time. Therefore, these galaxies are called cosmic destroyers.
Our current understanding of how the universe came to be is this. First, dark matter collapses into giant clumps called halos. This happened within the first few hundred million years after the Big Bang. The halo’s gravity then attracts normal matter. This eventually formed stars and galaxies.
This takes time. Matter will slowly gather together, eventually forming larger and larger galaxies. If true, the giant galaxies discovered by JWST shortly after the Big Bang should be impossible.
What’s more, the current cosmic story doesn’t predict the existence of enough dark matter halos in the early universe that were needed to build many of the large galaxies seen by JWST.
From this perspective, things look pretty scary for scientists’ current theories about how the universe evolved.
But Mutz and his colleagues believe it’s too early to overturn our current picture of the evolution of the universe. Perhaps scientists need to be more careful when interpreting JWST data, they say.
The Hubble Telescope is involved
Muozs’ team decided to use data from NASA’s Hubble Space Telescope to check the JWST results. Harper is older. And its eyesight isn’t that good either. So it can’t see as far back in time as JWST. But both instruments can capture the light emitted by galaxies over an era. This era spans approximately 450 million to 750 million years after the Big Bang. The James Webb Space Telescope observes these galaxies in infrared light. Hubble saw them in ultraviolet light.
If there was indeed 10 times more dark matter structure in the early universe than we thought, then there would also be 10 times more galaxies in the James Webb image, Mutz said.Hubble will also have 10 times more galaxies in it, he added. [data].
But the Hubble data shows otherwise.
The team counted the number of galaxies Hubble saw across a wide range of brightnesses. They then tried adding more dark matter haloes to their models of the early universe. If they add enough halo to match the JWST data, their model cannot match the Hubble data.
So which telescope should we trust?
JWST is the more powerful of the two. At a given distance, it can see more galaxies than Hubble. But Mutz points out that Hubble has been observing the universe for much longer. JWST will not begin collecting data until 2022.
For this reason, the researchers recommend looking for other explanations for JWST’s strange galaxies that don’t involve rewriting the history of the universe with new physics.
How is this going?
Scientists believe that the galaxies in the JWST images are very massive. They look very bright. But there may be other reasons for their brightness.
Conditions in the early universe may have been different from those later. This may allow gas and dust to transform into stars more efficiently than previously thought. Perhaps such rapid star formation creates the strangely bright objects seen by JWST.
Star formation may also be more intermittent. That is, there may have been quiet periods with little star formation, followed by periods filled with rapid star formation. The stars in each burst of star formation are nearly the same age. So they all die at the same time in explosive supernovae. In this case, JWST might just be catching some galaxies during these moments of intense brightness.
It’s also possible that some of the light seen by the James Webb Telescope in these early galaxies came from their centers. There, supermassive black holes may devour surrounding matter. This crazy feast will bring a lot of light. Overall, this can make galaxies appear super bright.
Other researchers were impressed by Muoz’s team’s findings.Very smart to see overlapping areas [between Hubble and JWST]” says Priyamvada Natarajan, a theoretical astrophysicist at Yale University.
But Erica Nelson points out that the universe isn’t completely safe yet. Nelson is an astrophysicist at the University of Colorado Boulder. She was part of the first team to discover the Universe Destroyer. If any of these objects are as big as they appear, that’s a problem, she said.
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