Astronomers have found a galaxy 13.1 billion light-years from Earth, making it officially the most distant object ever detected.
A faint, infrared speck of light from this ancient galaxy, called z8_GND_5296, was spotted using the Hubble Space Telescope and one of the world's largest ground-based telescopes, a ten-meter telescope at Keck Observatory at the summit of Mauna Kea, Hawaii.
Light from this baby galaxy began its journey when the universe was about 700 million years old and just emerging from the cosmic mist left over from its birth, said Casey Papovich, one of the lead authors of the study and an astronomer at Texas A&M University in College Station.
The former record holder is a fellow youngster, an ultra-faint galaxy about 100 million light-years closer to Earth.
Past claims of galaxies at these extreme distances were mined from deep field images taken by the Hubble Space Telescope. But many of these would-be candidates turned out to be much closer than previously thought, according to Papovich.
"Some of our candidates have turned out to be very cold stars—brown dwarfs—in our own galaxy," he explained.
The only way to confirm a galaxy's true distance, however, is to do follow-up measurements analyzing the spectrum of light emitted. This can enable astronomers to determine a candidate's redshift—how far its light is shifted into the red part of the spectrum—and thereby its distance.
Redshift occurs because wavelengths of light stretch out as galaxies move away from observers on Earth. So the higher the redshift number, the more distant the object from Earth.
Papovich's team found this faint galaxy's redshift was 7.5, compared with the previous record holder's 7.2.
"Until you have a redshift, there is always some doubt about the exact nature of the galaxy," said Papovich.
"All the other objects out there with claimed 'most distant galaxy' in their titles are candidates selected using only imaging, and no spectroscopic confirmation like what we have done here."
The find, described in a study published this week in the journal Nature, is expected to help researchers better understand the so-called era of reionization, when newborn hot, massive stars and their galaxies transformed the opaque hydrogen fog—which filled the cosmos in the first billion years after the Big Bang—into the transparent intergalactic space we see today.
"The galaxies themselves [in this era of the universe] would be filled with the newly formed, massive stars, many of which could be a thousand times the mass of our own sun," Papovich explained.
"We have yet to identify any conclusive evidence that these 'first-generation' stars exist in even this distant galaxy."
How Far Back Can We Go?
Can we push the record back even further, closer to the Big Bang?
Richard Ellis, an astronomer not connected to the study, says it is definitely possible. But we do not yet have telescopes powerful enough to do the job.
"We have the capability, in principle, to push to redshifts of ten and beyond, corresponding to a time when the universe was only 350 million years old, or only 3 percent of its present age," said Ellis, an astronomer at the California Institute of Technology in Pasadena.
The conundrum for researchers is that looking at larger distances means looking further back in time. That means galaxies become ever fainter as we push closer to the birth of the universe and the Big Bang.
"For most of the early galaxies being seen by Hubble, there's little hope of confirming their distances with spectroscopy until we get powerful new facilities such as the James Webb Space Telescope and the Thirty Meter Telescope," said Ellis.
"Ultimately, to chart the universe in detail at these early times, we need the next-generation facilities."