Scientists just announced They’ve discovered what may be some of the first galaxies to form in the universe, a tantalizing discovery made thanks to NASA’s new James Webb Space Telescope.
“This is the first large sample of candidate galaxies beyond the reach of the Hubble Space Telescope,” astronomer Haojing Yan said yesterday at a news conference at the American Astronomical Society meeting in Seattle. Yan, who works at the University of Missouri, led the newly published study. Because the more sensitive JWST telescope can see further into deep space than its predecessors, the Hubble, it is essentially seeing more time in the past. In the new catalog of 87 galaxies astronomers have discovered using them, some of them may date back about 13.6 billion years, just 200 million years after the Big Bang. That’s when the galaxies emitted the light we see today – although those systems of stars, gas and dust would have changed dramatically since then, if they still existed at all.
While scientists have studied other distant galaxies dating back to when the universe was still young, Yan and his colleagues’ discoveries could shatter those records by a few hundred million years or so. But at this point, they’re still considered “candidate galaxies,” which means their birthdates still need to be confirmed.
Determining a galaxy’s history can be tricky: it involves measuring its “redshift,” the amount of light it emits that stretches toward longer red wavelengths, which tells astronomers how fast the galaxy is moving away from us in the rapidly expanding universe. This, in turn, tells astronomers the galaxy’s distance from Earth — or more specifically, the distance photons from its stars must travel at the speed of light before they reach a near-Earth space telescope, such as JWST. The light from stars in the most distant galaxy in this cluster may have been emitted 13.6 billion years ago, likely shortly after the young galaxy consolidated.
These newly estimated distances must be confirmed using spectra, which means measuring the light that galaxies emit across the electromagnetic spectrum and identifying their unique signatures. Still, Yan expects many of them to be properly dated to the early days of the universe: “I’ll bet 20 dollars and a tall beer that the success rate will be above 50 percent,” he said.
Yan’s team imaged these galaxies with JWST’s NIRCam in six near-infrared wavelengths. To estimate their distances, astronomers used the standard “leakage” technique: hydrogen gas surrounding galaxies absorbs light at a specific wavelength, so the wavelengths at which an object can or cannot be seen put a limit on how likely it is. To be. These 87 candidate galaxies mostly look like blobs that can only be detected in the longer (and therefore redder) near-infrared wavelengths that can be detected by NIRCam, which could mean that they are very far away, and therefore very old.
However, it is possible that some of them are much closer than expected – which means they are not so old after all. For example, their light can be too dim to be detected at some wavelengths. Until Yan can collect more detailed data, he won’t know for sure.
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