A team of expert astronomers has rigorously analyzed GN-z11, long recognized as the earliest detected galaxy. Their precise observations confirm it as the most distant galaxy ever observed from Earth.
Discovered about four years ago in the constellation Ursa Major, GN-z11 was immediately hailed as the most distant and oldest galaxy in the observable universe. Hubble Space Telescope data indicated it formed roughly 13.4 billion years ago—mere 400 million years after the Big Bang.
In a groundbreaking study, Nobunari Kashikawa from the University of Tokyo and his team refined these estimates using the redshift technique, a cornerstone of modern cosmology.
As light from distant objects travels through expanding space, its wavelengths stretch toward the red end of the spectrum. The greater the distance, the more pronounced this redshift. By quantifying it, astronomers pinpoint a galaxy's distance with remarkable accuracy.
Published in Nature Astronomy, the research honed in on emission lines—distinct chemical signatures in the light from far-off galaxies. Measuring their stretch revealed precisely how far the light had traveled from GN-z11.
“We targeted ultraviolet light, where we anticipated finding these redshifted signatures,” explains Nobunari Kashikawa.
Using the MOSFIRE spectrograph on the WM Keck Observatory in Hawaii, the team measured GN-z11's redshift at z = 10.957 with 100 times greater precision. This solidifies its status as humanity's most distant observed object, formed when the universe was just 3% of its current age, 13.4 billion years ago.
Collaborating with Linhua Jiang's team from Peking University, the researchers noted that the key photons stemmed from a brief, intense flash. GN-z11 briefly flared hundreds of times brighter for under three minutes—likely the afterglow of a gamma-ray burst from a massive star's collapse.
