scientists just announced They’ve detected what may have been the first galaxies to form in the universe, a tantalizing discovery thanks to NASA’s new flagship James Webb Space Telescope.
“This is the first large sample of candidate galaxies not detectable by the Hubble Space Telescope,” its predecessor, Haojing Yan, an astronomer at the University of Missouri who led the newly published study, said during a news conference at a meeting of the American Astronomical Society yesterday. . in Seattle. Because the more sensitive JWST can see farther into the depths of space than Hubble, it can essentially see farther back in time. In a new catalog of 87 galaxies discovered by astronomers, some date back to about 13.6 billion years ago, or just 200 million years after the Big Bang. That’s when galaxies emitted the light we see today — though those systems of stars, gas and dust, if they still exist, have changed dramatically since then.
While scientists have studied other distant galaxies where the universe is still young, Yan and his colleagues’ findings could break those records by a few hundred million years or so. But at this point, they’re still considered “candidate galaxies,” meaning their birth dates still need to be confirmed.
Determining the age of a galaxy can be a challenging business: It involves measuring its “redshift,” the degree to which the light it emits is stretched to longer red wavelengths, which tells astronomers how fast How fast the galaxy is moving away from us in the expanding universe. That, in turn, tells astronomers its distance from Earth—or, more precisely, how far photons from its star must travel at the speed of light before reaching space telescopes like JWST near Earth. The light from the stars in the most distant galaxies in this collection may have been emitted 13.6 billion years ago, likely shortly after the young galaxies gathered.
These new estimates of galaxy distances had to be confirmed spectroscopically, meaning measuring the light they emit across the electromagnetic spectrum and pinpointing their unique signatures. Still, Yan hopes that many of them will be traced correctly to the early days of the universe: “I’d bet $20 and a mug of beer that the success rate would be better than 50 percent,” he says.
Yan’s team imaged them at six near-infrared wavelengths using JWST’s NIRCam. To estimate their distances, astronomers used a standard “dropout” technique: The hydrogen gas surrounding galaxies absorbs specific wavelengths of light, so the wavelengths at which an object is visible or invisible limits how far away it might become. Most of these 87 candidate galaxies look like blobs that can only be detected in the longer (and therefore redder) near-infrared wavelengths detectable by NIRCam, which could mean they are very distant and therefore very old.
However, some of them may be much more recent than expected—meaning they aren’t that old after all. For example, their light may be too faint to be detected at certain wavelengths. Until Yan collects more detailed data, he can’t be sure.
