The AS-gamma experiment site in the Tibet autonomous region. [Image: China Daily]

Scientists from China and Japan have spotted the highest-energy light particle ever observed on Earth, and they believed it came from one of the most mesmerizing celestial objects that has captivated poets and physicists alike since the 11th century - the Crab Nebula.

Capturing and studying these speedy space photons can help shed light on their mysterious origin and acceleration mechanism, leading to new revelations about the，extreme conditions of the universe, scientists said.

The Tibet AS-gamma experiment, a China-Japan joint research project located about 4.3 kilometers above sea level in the Tibet autonomous region, has discovered 24 photons with energies above 100 trillion electron volts (TeV), one of which even registered a staggering 450 TeV.

These findings represent the first detection of high energy photons over 100 TeV and the highest ever recorded. “It is a milestone for super-high-energy gamma-ray astronomy,” said Huang Jing, a spokeswoman for the project and a researcher from the Institute of High Energy Physics of the Chinese Academy of Sciences.

The previous record energy level was 75 TeV, observed by the HEGRA Cherenkov telescope.

Huang said they believe these photons originated from the Crab Nebula, the remnant of a supernova that was observed in 1054 AD, around 6,500 light years away from Earth.

The research results will be published later this month in the journal Physical Review Letters.

The stellar event that led to the Crab Nebula was recorded in official histories of the Song Dynasty (960-1279) in ancient China, as well as in Meigetsuki, a literary diary by 12th century Japanese poet Fujiwara no Teika.

In 2005, NASA’s Hubble Telescope released the most detailed optical view of the entire nebula, calling it “the most interesting and well-studied object in astronomy”.

However, since the discovery of cosmic rays - energetic, subatomic particles from space - in 1912, scientists have been baffled by how the universe can accelerate particles to close to the speed of light and make them travel for hundreds, if not millions of light years through space.

Scientists hypothesized that the highenergy cosmic rays might have generated from massive stellar explosions or black holes. “But one thing is now certain, and that is the Crab Nebula is the most powerful natural electron accelerator currently known in our galaxy,” Huang said.“The recent discoveries open a new window for the exploration of the extreme universe and are key to understanding the fundamental physics in extreme conditions,” she added.

In 1991, scientists from the United States discovered the highest energy particle to ever reach Earth, a proton with 300 million TeV. They dubbed it the “Oh- My-God” particle for its mind-boggling speed and energy.

Visible light, for comparison, has just a few electron volts of energy. The Large Hadron Collider, the world’s most powerful particle smasher, only has a maximum designed collision energy of 14 TeV.

While the Earth is being constantly bombarded with cosmic rays, it is still very difficult to detect a high-energy particle given interferences from Earth’s atmosphere and other disturbances.

As a result, the Tibet AS-gamma experiment, jointly operated by China and Japan since 1990, built an observatory across an area of more than 65,000 square meters in high altitudes to reduce noise and improve sensitivity.

In 2014, scientists from China and Japan added new underground detectors that can suppress 99.92 percent of the cosmic-ray background noises. That addition, along with other innovative upgrades, led scientists to finally discover the high-energy photon they were looking for, Huang said.

Chen Yang, a professor of astronomy from Nanjing University, said with a deeper understanding of cosmic rays, scientists can increase the efficiency for space breeding, the process of improving crop species via mutations caused by exposure to extreme conditions in space.

Source: China Daily