Ancient starlight, emitted by the first stars in the universe, has been detected using the Fermi Gamma-ray Space Telescope.
Marco Ajello, an astrophysicist at the University of California, Berkeley, and his colleagues report the finding in the current issue of the journal Science. Dr. Ajello conducted the research while working at Stanford University.
"These were probably the very first objects to form in our universe," he said. "They formed just about 500 million years after the Big Bang."
Scientists suggest that the Big Bang occurred about 13 billion years ago, resulting in the creation of our universe, which continues to expand.
The first stars in the universe were massive and primarily made up of hydrogen. They probably burned through the hydrogen quickly and exploded into supernovas early on. Although those original stars are long gone, the light from them is still traveling to us, Dr. Ajello said.
Measuring the ancient starlight directly was impossible because the light from our own galaxy is overpowering. So instead, the researchers used gamma rays. For this, they relied on blazars, faraway galaxies that emit gamma rays.
"They are like lighthouses farther and farther away from us," Dr. Ajello said. "They are located at different distances from us, and from them we are able to measure the amount of starlight in different epochs."
The researchers collected data on light in the universe 4 billion years, 8 billion years and 11 billion years after the Big Bang. In the future, Dr. Ajello hopes to take measurements at points even closer to the beginning of the universe.
"Since the universe is always expanding, the best way to measure is to go as early as possible in the history of the universe," he said. "Two billion or one billion years after the Big Bang will give us more accurate measurements."
This article originally appeared in The New York Times.