Exceptionally high rate of star formation in the galaxy, formed a mere 700m years after the big bang, has baffled astronomers

Astronomers have spotted the most distant galaxy ever seen after a faint ray of light struck a telescope on a volcano in the middle of the Pacific.

The ancient group of stars lies 30bn light years from Earth, far beyond the handle of the Big Dipper that traces a celestial saucepan in the constellation of Ursa Major.

Researchers detected the galaxy with a new infrared instrument that was fitted last year to the Keck telescope that sits on the summit of Mauna Kea, a dormant volcano in Hawaii.

Analysis of light coming from the galaxy showed that it formed only 700m years after the big bang, or 13.1bn years ago, making it the oldest and most distant galaxy known.

"This is really a quest to understand our origins," said Steve Finkelstein, an astronomer at the University of Texas at Austin. "By trying to push further and further back in time, we are really studying the origins of our own Milky Way galaxy."

Because the universe is expanding, light from stars and other celestial objects is stretched out as it travels through space. This increases its wavelength. The effect is called redshift because it makes visible light look redder.

Finkelstein used the Mosfire (Multi-Object Spectrometer for Infra-red Exploration) instrument on the Keck telescope to survey 43 distant galaxies that had been glimpsed by the Hubble Space Telescope but never confirmed.

The device picked up light from only one, a galaxy that goes by the cumbersome name of z8_GND_5296, according to a report in the journal Nature.

The light coming from the galaxy was more redshifted than astronomers had seen before, making it 40m years older than the previous record holder. The colour of the galaxy suggested it was rich in metals.

Early measurements showed that the mass of the galaxy's stars was equivalent to 1bn suns, which is 40 to 50 times less than the Milky Way's stellar mass. What surprised astronomers most was the intense rate the galaxy was churning out stars, around 150 times faster than the Milky Way.

"We didn't think you could make galaxies with such intense star formation rates in the early universe. Star formation tends to be proportional to the mass of a galaxy, and the masses of galaxies in the early universe tend to be small," said Finkelstein.

The scientists have a couple of potential explanations for the galaxy's extraordinary rate of star creation. It may contain more gas than expected, which is used in the manufacture of stars. Or it may be drawing in gas much faster from the space between galaxies. Finkelstein hopes that follow-up observations will now answer the question.

The search for distant galaxies is driven by the aim to find, ultimately, the first ones to form in the universe. These galaxies could have been home to stars that produced the first batch of natural elements heavier than helium when they exploded at the end of their lives.

Astronomers may struggle to find more distant galaxies with telescopes operating today. But towards the end of the decade, Nasa expects to launch the James Webb Space Telescope, which has been designed to look further back into the history of the universe.

• This article was amended on 24 and 29 October 2013. The original stated that the newly measured galaxy was 40bn to 50bn times lighter than the Milky Way. This has been corrected to say that the mass of the galaxy's stars is 40 to 50 times less than the Milky Way's stellar mass.