Massive blue stars that formed the first chemical elements necessary for life likely occupy a bright, distant galaxy studied by astronomers using the Keck Observatory on Mauna Kea.

The galaxy, named Cosmos Redshift 7, or CR7, is also extremely young, only 800 million years old, meaning its light has traveled nearly 13 billion light-years to reach the Keck spectrographs.

"We confirmed that the galaxy is more than 12 billion light-years from us," said Bahram Mobasher, a professor of physics and astronomy at the University of California at Riverside, in a statement Wednesday. 

"Combining these with other observations, the UCR team successfully identified the presence of ions from elements that could only be produced through intense radiation."

Astronomers have long theorized the existence of a first generation of stars born out of the primordial material from the big bang. All the heavier chemical elements — including oxygen, nitrogen, carbon and iron, which are essential to life — were forged in these stellar crucibles.

This means that the first stars must have formed out of the only elements to exist before stars: hydrogen, helium and trace amounts of lithium.

"These elements are responsible for forming stars and galaxies and for originating life," Mobasher said. "Discovery of light from these stars confirms the long-standing theoretical predictions regarding the existence of such stars early in the history of the universe."

Such stars could have been hundreds or thousands of times as massive as the sun, according to calculations, and burning brightly and dying quickly, only 200 million years after the universe began. Their explosions would have spewed into space the elements that started the chain of thermonuclear reactions by which subsequent generations of stars have gradually enriched the cosmos with elements like oxygen, carbon and iron.

Mobasher worked with graduate students Behnam Darvish and Shoubaneh Hemmati, while other astronomers, led by David Sobral of the University of Lisbon, Portugal, worked with the European Southern Observatory’s Very Large Telescope, the Hubble Space Telescope and the Subaru Observatory on Mauna Kea.

The research paper has been accepted for publication in the Astrophysical Journal.

Spotting the older stars in action is one of the prime missions of the James Webb Space Telescope, to be launched by NASA in 2018. The discovery of such stars "would be wonderful," James Peebles, a Princeton professor and one of the fathers of modern cosmology, said recently.

Galaxy CR7 is three times as luminous as any previously found from that time, the authors said. Within it is a bright blue cloud that seems to contain only hydrogen and helium.

In an email, Sobral called this the first direct evidence of the stars "that ultimately allowed us all to be here by fabricating heavy elements and changing the composition of the universe."

In a statement from the European Southern Observatory, he said, "It doesn’t really get any more exciting than this."

Garth Illingworth, an astronomer at the University of California, Santa Cruz, and a veteran of the search for early galaxies, pointed out, however, that these stars were appearing far later in cosmic history than theory had predicted.

Sobral and his colleagues were using the Very Large Telescope of the Southern Observatory in Chile and Keck, among other big telescopes, to build on an earlier search for glowing clouds of hydrogen that might represent very early galaxies. Galaxy CR7 stood out.

In an expanding universe, the farther away or back in time an object is, the faster it is receding, which causes the wavelength of light from it to lengthen, the way the pitch of a siren sounds lower after it passes. In astronomy this lengthening is known as redshifting.

The galaxy’s name, Sobral said, was also inspired by the great Portuguese soccer player Cristiano Ronaldo, aka CR7.

As in much of astronomy, the nomenclature of these star generations is awkwardly rooted in history and Earth-centered. Modern stars like the sun, with healthy abundances of so-called metals (anything heavier than helium), are now called Population I, mainly because they were the first known. They mostly inhabit the spiral arms and younger parts of galaxies like the Milky Way.

In the middle of the 20th century, however, astronomer Walter Baade noticed that the stars in older parts of the galaxy, like its core or globular clusters, are older and have fewer metals. He called them Population II.

The advent of the big-bang theory of the origin of the universe forced astronomers to realize that the first stars must have had no metals at all; those are known as Population III.

Stars of both Population II and Population III are probably present in CR7, Sobral and his team report. While the blue cloud is metal-free, according to spectral measurements, the color of the rest of the galaxy is consistent with more evolved stars making up most of its mass. This suggests, they write, that the Population III stars there are late bloomers of a sort, forming from leftover clouds of pristine material as the galaxy was sending out its light 12.9 billion years ago.

The only alternative explanation, Sobral said, is something so spectacular and unlikely that astronomers do not know whether it has ever happened, namely a primordial cloud bypassing the star stage and collapsing directly into a black hole. That, he noted, is impossible to rule out because nobody really knows what it should look like.

Further observations with the Hubble Space Telescope and the James Webb could help resolve the issue.