Scientists on the hunt for the first galaxies formed after the universe’s creation have a new milestone -- an unexpectedly active galaxy that existed just 700 million years after the Big Bang.
The long-distance champ, known by its catalog number z8_GND_5296, first revealed itself in the Hubble Space Telescope’s infrared camera. Follow-up investigations with a new infrared light-splitting spectrograph at the Keck Observatory confirmed the galaxy’s location.
“If you tried to look at these really distant galaxies with a visible light telescope you would see nothing. Literally, they’re invisible. All that visible and optical light has been shifted into the near-infrared,” astronomer Steven Finkelstein, with the University of Texas at Austin, told Discovery News.
The shift, known as the Dopper effect, is due to the expansion of the universe and the speed at which the galaxies are moving away. It is similar to the shifting sound of an approaching train.
Oddly, z8_GND_5296 was the only one of 43 galaxy candidates that clearly radiated the telltale chemical fingerprint of a particular hydrogen emission astronomers needed for their celestial measuring sticks.
That in and of itself is fodder for a host of questions about the universe’s early years, particularly when and how quickly photons of light from the first galaxies could navigate intergalactic hydrogen gas without being scattered.
For light to be detected, the hydrogen needs to be ionized, a phenomenon that, somewhat paradoxically, is believed to have been triggered by the first generation of galaxies.
“To look at galaxies that are very distant is particularly interesting because light travels at a finite speed, so essentially the more distant a galaxy is the more time the light takes to get toward us. This means that by looking at distant galaxies we can probe the past history of the universe. We essentially see the galaxy at the point in time when the light was emitted,” astronomer Dominik Riechers, with Cornell University, told Discovery News.
“This galaxy is so far away that any light we receive from it travels for 13.1 billion years before it reaches us. What we’re really seeing is the universe as it looked like 13.1 billion years ago, which is only 700 million years of the Big Bang,” he said.
Aside from confirming z8_GND_5296’s extreme distance, the galaxy turned out to be producing stars at prodigious rate, pumping out the equivalent of 330 masses the size of the sun every year. That is more than 100 times the rate of star formation of the Milky Way galaxy.
“The early universe may harbor a larger number of intense sites of star formation that expected,” Finkelstein wrote in a paper published in this week’s Nature.
He and colleagues also were surprised by the galaxy’s unexpectedly high percentage of oxygen and other so-called metals -- elements heavier than hydrogen and helium.