Astronomers have spotted the most distant galaxy yet, one that was formed about 700 million years after the universe is thought to have come into existence.
The newly discovered galaxy, designated z8_GND_5296 by scientists, is located 30 billion light-years away, according to researchers who published their findings Wednesday in the journal Nature.
"We are learning so much about a region so far back in time, it's hard to comprehend," said Steven Finkelstein, the lead researcher and an assistant professor at the University of Texas at Austin. "This galaxy we're seeing is almost 13.1 billion years ago, and so this was something like 8 billion years before our sun was even born and, of course, much longer after that until life came around."
Researchers found the galaxy using the Hubble Space Telescope and Keck Observatory in Hawaii, both of which detected it in infrared light.
Surprisingly, out of a pool of 43 candidate distant galaxies, z8_GND_5296 was the only one that revealed the key chemical evidence needed to confirm its distance.
That left Finkelstein and colleagues wondering if they had uncovered a clue to a bigger mystery: How soon did light from the universe's first stars and galaxies pierce an obscuring veil of hydrogen gas that existed early in its history?
Scientists believe that at some point, high-energy ultraviolet radiation from exploded stars split intergalactic hydrogen atoms into electrons and protons. Once ionized, the hydrogen would be electrically conductive and no longer scatter light.
That may have happened about the time of z8_GND_5296's existence.
The galaxy, which is about a billion times as massive as the sun, has two unusual characteristics, which may determine why it is visible while potential sister galaxies are not.
First, z8_GND_5296 is forming stars at a very fast pace, producing about 100 times more stars than our Milky Way, so it may be brighter than the other candidate galaxies.
Second, it contains a surprisingly high percentage of elements heavier than hydrogen and helium.
Those elements are forged by nuclear fusion inside stars, so either the galaxy contains the exploded remains of lots of massive stars or it formed in a region of space that had been seeded with the remnants of a prior generation of stars, scientists said.
"It could be that this one galaxy lives in an overdense region of (ionized hydrogen) so we can see it ... but that's a little bit of conjecture," Finkelstein said. "For all we know, these other galaxies have just a lot more hydrogen gas within the galaxies themselves and that's why we can't see them."