Back in the day of GN-z11, galaxies were made of stronger stuff and it just doesn’t understand young whipper-snappers like the Milky Way. Such is the life of older galaxies. In this case, the oldest that we know of. So distant, in fact, it defines the very boundary of the observable universe itself.
Professor Nobunari Kashikawa from the Department of Astronomy at the University of Tokyo sought the most distant galaxy one can observe in order to find out how and when it came to be. In his quest, he and his team were able to more accurately find the distance to the aging galaxy.
While it has been known for a while that GN-z11 was the oldest known galaxy, measuring the distance to it turned out to be quite the challenge.
“From previous studies, the galaxy GN-z11 seems to be the farthest detectable galaxy from us, at 13.4 billion light years, or 134 nonillion kilometers (that’s 134 followed by 30 zeros),” said Kashikawa. “But measuring and verifying such a distance is not an easy task.”
In order to measure the distance, Kashikawa measured the redshift, or how much light has shifted toward the red end of the spectrum as galaxies move away from each other with the universal expansion. The farther away the galaxy is, the more redshift. Using the Keck I telescope, the astronomers were able to get a decent fix on GN-z11.
“We looked at ultraviolet light specifically, as that is the area of the electromagnetic spectrum we expected to find the redshifted chemical signatures,” said Kashikawa. “The Hubble Space Telescope detected the signature multiple times in the spectrum of GN-z11. However, even the Hubble cannot resolve ultraviolet emission lines to the degree we needed. So we turned to a more up-to-date ground-based spectrograph, an instrument to measure emission lines, called MOSFIRE.”
When working with distances at these enormous scales, it just isn’t sensible to use our familiar units of kilometers and miles, or even multiples of them. Instead, astronomers use a value known as the redshift number denoted by z.
Using MOSFIRE (Multi-Object Spectrometer For Infra-Red Exploration), the team captured the emission lines from GN-z11 in detail, which allowed them to make a much better estimation on its distance than was possible from previous data, confirming the galaxy’s ‘farthest’ status.
The study was published in the journal Nature Astronomy on December 14.