A hot cluster of stars whose light began travelling to Earth just 700 million years after the Big Bang has been confirmed as the most distant galaxy ever detected.
The galaxy, code named z8-GND-5296, emitted the light detected by astronomers when the universe was only about 5% of its current age of 13.8 billion years.
Analysis of the light shows that the galaxy is rich in metal, and generating a surprising number of new stars. Scientists estimate its star formation rate to be hundreds of times faster than that of our own galaxy, the Milky Way.
The research, published in the journal Nature, is based on measurements of "red shift" - the way light waves from a fast-moving object are stretched towards the red end of the spectrum as its distance increases.
A similar phenomenon causes the pitch of a police car siren to fall as its speeds away. In the expanding universe, very distant objects are receding at a rapid rate, causing their colour spectrum to shift dramatically.
Astronomers first spotted the galaxy in a survey of distant objects conducted with the Hubble Space Telescope.
A highly sensitive instrument at the Keck observatory in Hawaii, designed to detect infrared light, confirmed the galaxy's distance. It showed the the object to have a redshift of 7.5, beating the previous record of 7.2.
Lead scientist Professor Bahram Mobasher, from the University of California at Riverside, US, said: "By observing a galaxy that far back in time, we can study the earliest formation of galaxies. By comparing properties of galaxies at different distances, we can explore the evolution of galaxies throughout the age of the universe.
"With the construction and commissioning of larger ground-based telescopes... by the end of this decade we should expect to find many more such galaxies at even larger distances, allowing us to witness the process of galaxy formation as it happens."