‘Major’ feat by Chinese telescope as one of biggest cosmic blasts since big bang hits Earth
- Intense gamma-ray burst from distant galaxy more than 2 billion years ago is captured by Chinese observatory on Tibetan Plateau
- Detection by the Lhaaso observatory ‘a major scientific event’, says astrophysicist in Munich
Astronomers around the world have just witnessed one of the most powerful explosions in the universe since the big bang, and they are racing to decipher and reveal the details.
More than 2 billion years ago in the direction of the constellation Sagitta, a massive, dying star exploded and collapsed into a black hole, spewing a fiery jet of light into space.
The burst was so bright that it blinded the detectors of some telescopes and left them with completely white pixels, said HEBS chief scientist Xiong Shaolin, who is from the Institute of High Energy Physics at the Chinese Academy of Sciences in Beijing.
The record-breaking space event, named GRB 221009A, was at least 10 times brighter than previous gamma-ray bursts and released the amount of energy that would take thousands of suns their entire lifetimes to produce.
The explosion was soon confirmed by China’s Large High Altitude Air Shower Observatory (Lhaaso), located on the Tibetan Plateau in Sichuan province.
Lhaaso chief scientist Cao Zhen, who is also with the institute in Beijing, said that among the thousands of light particles detected by the cosmic ray observatory within the first 30 minutes, the most energetic one reached 18 tera-electron-volts (TeV), which was “totally unexpected and extraordinary”.
The maximum energy level not only shattered the previous record – detected by the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes in Spain in 2019 – by a factor of 10, but was also theoretically intriguing because high-energy particles are usually absorbed by starlight or stardust on their way to Earth.
For instance, a 1 TeV gamma light particle can interact with a 1 electron volt infrared light particle to produce an electron and its antiparticle, thus disappearing from the initial light beam, according to Razmik Mirzoyan at the Max Planck Institute of Physics in Munich, Germany.
Only about one out of 1,000 light particles with TeV-level energy could survive to reach the Earth after travelling through space for billions of years, he said.
“Lhaaso’s wide field of view, combined with its sensitivity, makes it a very powerful detector for measuring diverse classes of cosmic and gamma rays at very high energies,” said the astrophysicist and former spokesman for MAGIC.
Located 4,410 metres (about 14,470 feet) above sea level, Lhaaso consists of four types of detectors and spans 1.3 square km. When GRB 221009A first hit Earth on October 9, it fortunately fell right into Lhaaso’s field of view, Cao said.
Gamma-ray bursts are the most energetic outbursts in distant galaxies. They are believed to be produced during the collapse of massive stars, or when two space objects merge, such as black holes or neutron stars.
Scientists have detected thousands of gamma-ray bursts since the 1960s. Xiong said that when GRB 221009A was first spotted, it was so bright that astronomers mistook it for some explosion within the Milky Way.
Using optical telescopes, they were able to determine the distance between its source and Earth. “Actually it’s one of the closest gamma-ray bursts that has ever happened – something that only occurs every few decades or even once a century,” Xiong said.
He remembered working in the US on another bright and close gamma-ray burst, detected by Nasa’s Fermi telescope in 2013. Back then, China did not have any X-ray or gamma-ray detectors.
HEBS is still in the commissioning phase after entering orbit in July as an all-sky monitor of gamma-ray events on board a space technology demonstration satellite.
The Insight-HXMT, on the other hand, is China’s first X-ray astronomy satellite. Envisioned in the 1970s and launched in 2017, it has made a series of discoveries including measuring the strongest magnetic field in the universe.
Chinese astronomers and their international colleagues are working hard to better understand GRB 221009A, using observation data from both the explosion and the fading fireball that followed – known as the afterglow.
“In an event like this, a supernova is expected to show up about two weeks after the explosion,” said Bing Zhang from the University of Nevada, Las Vegas.
Many ground-based optical telescopes, including the Gemini South Telescope in Chile, are also scrambling to spot the supernova.
Astronomers are just really excited, Zhang said. The event’s proximity to Earth and the brightness of the energy burst could make it one of the most studied cosmic explosions in history.