The biggest explosions since the Big Bang set the universe in motion some 13 billion years ago produced even more energy than first thought, scientists said Wednesday.
In a study published in Nature, two international teams describe how they searched for the Gamma-ray Bursts (GRB) produced when neutron stars collide or giant suns collapse into a black hole, forming a supernova.
"Gamma-ray bursts are the most powerful explosions known in the Universe and typically release more energy in just a few seconds than our Sun during its entire lifetime," said David Berge, head of gamma-ray astronomy at Deutsches Elektronen-Synchrotron (DESY) in Hamburg, Germany.
GRBs can last anywhere from a few milliseconds to several hours and, while enormous in terms of energy, they are a relatively rare phenomenon.
They were first discovered by chance in the 1960s by satellites used to monitor compliance with the nuclear test ban on Earth.
Since then, astronomers have tracked them from above Earth's atmosphere, which absorbs gamma rays.
For this study they instead used ground-based telescopes to observe events billions of light years from our planet.
In mid-2018 and January 2019, the two teams -- alerted by NASA satellite observations -- detected gamma rays from two GRB events using the High-Energy Stereoscopic System (H.E.S.S.) in Namibia and then the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes on La Palma, Spain.
"We were able to point to the region of origin so quickly that we could start observing only 57 seconds after the initial detection of the explosion," Cosimo Nigro from the MAGIC group at DESY, said in a summary of the article.
The results showed "by far the highest energy photons ever discovered from a gamma-ray burst", said Elisa Bernardini, leader of the MAGIC group at DESY.
More scientists followed up quickly, targeting one event more than four billion light years away and another at six billion light years. This allowed scientists to get a better understanding of the mechanics of the phenomenon.
DESY researcher Konstancja Satalecka said the findings helped straighten out the "energy budget" involved.
"It turns out we were missing approximately half of their energy budget until now," she said.
"Our measurements show that the energy released in very-high-energy gamma-rays is comparable to the amount radiated at all lower energies taken together. That is remarkable!"
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