There are tens, hundreds, or even 1000 times more bright galaxies at the edge of space-time (soon after the big bang) than astronomers had predicted, according to the James Webb Space Telescope, which has only been observing the sky for a few weeks.
“No one was expecting anything like this,” says Michael Boylan-Kolchin of the University of Texas, Austin. “Galaxies are exploding out of the woodwork,” says Rachel Somerville of the Flatiron Institute.
As gas clouds are believed to condense into stars and galaxies much more slowly than is suggested by Webb's galaxy-rich photos of the early universe, taken less than 500 million years after the big bang, galaxy formation models may now need to be revised.
Garth Illingworth of the University of California (UC), Santa Cruz, argues that this is "way outside the box" of what the models were forecasting.
Late in June, the NASA-led Webb orbiting observatory, which also received funding from the Canadian and European space agencies, started taking observations from its vantage position 1.5 million kilometers away from Earth.
It has spent most of its time up to this point working on demonstration projects like the Cosmic Evolution Early Release Science (CEERS) Survey. The Webb Space Telescope is intended to explore cosmic history more thoroughly than the Hubble Space Telescope.
|The James Webb Space Telescope captured this galaxy at a record distance.SOPHIE JEWELL/CLARA POLLOCK
Webb is more sensitive to such distant sources, whose light is stretched to longer, redder wavelengths by cosmic expansion, thanks to its 6.5-meter mirror, which has six times the area of Hubble's and operates at infrared wavelengths.
Within days of starting its observations, Webb discovered a candidate galaxy that would have been the farthest distant object ever observed if it had been visible when the universe was only 230 million years old or 1.7% of its present age.
Surveys conducted since then have revealed that the object is just one of a dazzling array of early galaxies, each of which is modest by modern standards but has a higher luminosity than anticipated.
According to photos of a small piece of sky, some scientists warn that the abundance may be a mirage. Boylan-Kolchin questions whether Webb simply "lucked out" and gazed into a massive cluster of galaxies that was denser than the rest of the early universe.
When CEERS expands its scope later this year and results from additional comprehensive surveys are available, that question will be answered.
A few of these posing galaxies have already been found by Webb's early scientific teams, as they report in a number of recent preprints. However, astronomers may have to fundamentally rethink galaxy formation or the dominant cosmology if the abundance of early galaxies is real.
According to Charlotte Mason of the Niels Bohr Institute, research using Hubble has revealed that star formation has been occurring at a comparatively consistent rate for up to 600 million years after the big bang. However, the Webb data suggest that in earlier eras, it was moving at a far faster rate—so quickly, that gas clouds were collapsing without any restraint from heat or supernovae.
In fact, Tommaso Treu of the University of California, Los Angeles, who is in charge of the GLASS Webb survey, claims that his team is observing these young galaxies "form stars like crazy." They look, he adds, “like giant balls of star formation and nothing else.”
James Webb is already breaking many astronomical records and we can't wait to see what's next.