The James Webb Space Telescope (JWST) is expected to provide groundbreaking insights into the early universe, and its images may call into question some of our current theories about how the universe evolved.
Astronomers discovered that six of the earliest and most massive galaxy candidates observed by the James Webb Space Telescope appear to have converted nearly 100% of their available gas into stars, contradicting the dominant cosmological model. If the standard model of cosmology is to be believed, the James Webb Space Telescope (JWST) appears to be discovering multiple galaxies that grew too massive too soon after the Big Bang.
Mike Boylan-Kolchin, an associate professor of astronomy at The University of Texas at Austin, discovers in a study published in Nature Astronomy that six of the earliest and most massive galaxy candidates observed by JWST so far stand to contradict prevailing cosmological thinking. This is due to the fact that other researchers estimate that each galaxy is visible between 500 and 700 million years after the Big Bang and is more than 10 billion times as massive as our sun. One of the galaxies appears to be more massive than the Milky Way, despite the fact that our own galaxy formed and grew over billions of years.
“If the masses are right, then we are in uncharted territory,” Boylan-Kolchin said. “We’ll require something very new about galaxy formation or a modification to cosmology. One of the most extreme possibilities is that the universe was expanding faster shortly after the Big Bang than we predict, which might require new forces and particles.”
If the masses are right, then we are in uncharted territory. We’ll require something very new about galaxy formation or a modification to cosmology. One of the most extreme possibilities is that the universe was expanding faster shortly after the Big Bang than we predict, which might require new forces and particles.
Boylan-Kolchin
For galaxies to form so fast at such a size, they also would need to be converting nearly 100% of their available gas into stars.
“We typically see a maximum of 10% of gas converted into stars,” Boylan-Kolchin said. “So while 100% conversion of gas into stars is technically right at the edge of what is theoretically possible, it’s really the case that this would require something to be very different from what we expect.”
JWST, for all of its breathless excitement, has presented astronomers with an unsettling quandary. If the masses and time since the Big Bang for these galaxies are confirmed, fundamental changes to the dominant model of cosmology, known as the dark energy + cold dark matter (CDM) paradigm, which has guided cosmology since the late 1990s, may be required. If there are other, faster ways to form galaxies than CDM allows, or if more matter was available for forming stars and galaxies in the early universe than previously thought, astronomers will need to reconsider their current assumptions.
The times and masses of the six galaxies are preliminary estimates that will need to be confirmed using spectroscopy, a method that divides light into a spectrum and analyzes the brightness of different colors. Such analysis could imply that central supermassive black holes, which could heat up the surrounding gas, are making galaxies brighter, making them appear more massive than they are. Perhaps the galaxies are seen at a much later time than was previously estimated due to dust that causes the color of the light from the galaxy to shift redder, giving the illusion of being more lightyears away and thus further back in time.
The galaxy data came from the Cosmic Evolution Early Release Science Survey (CEERS), a JWST collaboration led by UT Austin astronomer Steven Finkelstein.
COSMOS-Web, a collaborative JWST project co-led by UT Austin’s Caitlin Casey, may be involved with spectroscopy and shedding more light on the findings to help resolve the quandary. COSMOS-Web will discover thousands of galaxies over an area roughly 50 times larger than CEERS.
“It will be ideal for discovering the rarest, most massive galaxies at early times, which will tell us how the biggest galaxies and black holes in the early universe arose so quickly,” said Boylan-Kolchin.
The initial discovery and estimates of the six galaxy candidates’ masses and redshifts were published in Nature in February by a team led by Swinburne University of Technology in Australia.
