James Webb Spots the Farthest Galaxy Humans Have Ever Seen, Near the Dawn of Time

Scientists think they have discovered the most distant—and potentially oldest—galaxy ever seen in the universe using new observations from the James Webb Space Telescope (JWST), the most powerful observatory ever launched, according to a study posted on the preprint server arXiv on Tuesday. 

It has only been a week since the release of the first public images from JWST, which is a collaboration between NASA, the European Space Agency, and the Canadian Space Agency, but astronomers have already produced a deluge of new research about much-anticipated data from the telescope.

Among the wealth of new findings is a study led by Rohan Naidu, a graduate student in astronomy at Harvard University, announcing the discovery of a galaxy called GLASS-z13 that appears to exist just 300 million years after the Big Bang, according to the research. 

That potentially makes it much farther and older than other recent record-holders for the earliest known galaxy, including GLASS-z11, which was spotted about 400 million years after the Big Bang by NASA’s Hubble Space Telescope in 2016, reports New Scientist. Another galaxy, called HD-1, was also recently discovered at just 330 million light years after the Big Bang.

Since these are preliminary findings, the researchers still refer to the galaxies as “candidates” and caution that more research will be needed to confirm that GLASS-z13 really is the farthest and earliest known galaxy. They note that “JWST is a completely new facility for which calibration is still ongoing” which inevitably leads to uncertainties, according to the study. 

“It is potentially the most distant galaxy ever, but we can't tell if it is the oldest,” Naidu said in an email. “Specifically, we might be observing it as it was ~300 [million years] after the Big Bang. It could have just formed recently, or could have formed even farther back—we can't quite tell yet.”

“We would like to confirm it as the *most distant* known galaxy via spectroscopy,” referring to the chemical lines in the galaxy’s light that contain clues about its distance from Earth, Naidu added.

JWST glimpsed GLASS-z11 and GLASS-z13 at such an early stage in their formation that they only measure about 2,000 light years across, which is minuscule compared to the 100,000-light-year diameter of our own mature galaxy, the Milky Way. Likewise, these galactic elders are about one billion times as massive as the Sun, whereas the Milky Way has accumulated a mass of about 1.5 trillion Suns over more than 13 billion years.

While the galaxies are small compared to modern galaxies, they are unexpectedly large considering the early era they are in. 

“The most surprising thing is how massive and bright these galaxies have gotten so fast—billion solar galaxies, so early in the Universe, are expected by several leading models of galaxy formations to be rather rare!” Naidu said. “But our search is showing, perhaps not…”

Naidu and his colleagues also describe the galaxies as “remarkably luminous” in the study, which will help astronomers extract important details about their features, as well as the broader mysteries of galactic evolution in the early universe. 

“These two objects already place novel constraints on galaxy evolution in the cosmic dawn epoch,” the team said in the study. “They indicate that the discovery of GNz11 was not simply a matter of good fortune, but that there is likely a population of [ultraviolet] luminous sources with very high star-formation efficiencies.”

Indeed, GLASS-z11 and GLASS-z13 probably belong to a much larger population of galaxies that has remained out of view, but that JWST could spot at the edge of space and time.   

“If these candidates are confirmed spectroscopically,” the study concluded “it is clear that JWST will prove highly successful in pushing the cosmic frontier all the way to the brink of the Big Bang.”