Astronomers have detected one of the most powerful cosmic rays ever observed – and it was beamed towards Earth from a mysterious part of deep space.
The cosmic phenomenon had an energy of 240 quintillion electron volts – that’s 240 billion billion (followed by 18 zeros).
For comparison, a typical lightning bolt is about 300 million volts.
The cosmic ray – named Amaterasu, after the sun goddess in Japanese mythology – was detected by a telescope system in Utah in May 2021 by scientists who described it as “unprecedented” in modern times.
In addition to being one of the most powerful cosmic rays ever observed, Amaterasu may also come from an invisible corridor, or “void… in the universe.”
Scientists used the Telescope Array in Utah to track the direction of the ultra-high energy cosmic rays by recording which detectors lit up and in what order. The problem is that they still don’t know where it comes from
Cosmic rays are clusters of small, high-energy particles that move through space at nearly the speed of light.
They are often detected by instruments on Earth and usually result from solar flares or explosions on the Sun.
But scientists say Amaterasu could only have emerged from the most powerful celestial events – much bigger than a star explosion.
Professor Toshihiro Fujii of Osaka Metropolitan University in Japan, who observed the phenomenon captured by the Telescope Array experiment in Utah.
He said: ‘When I first discovered these ultra-high energy cosmic rays, I thought there must have been a mistake as it showed an energy level unprecedented in the past thirty years.
‘No promising astronomical object has been identified that matches the direction from which the cosmic rays came, suggesting possibilities of unknown astronomical phenomena and new physical origins beyond the Standard Model.’
John Matthews, research professor at the Department of Physics and Astronomy at the University of Utah in the US, said: ‘Things that people consider energetic, such as a supernova, are not nearly energetic enough for this.
‘You need enormous amounts of energy, very high magnetic fields to trap the particle while it is accelerated.’
At 240 quintillion electron volts (EeV), the Amaterasu particle has an energy second only to the Oh-My-God particle, another ultra-high energy cosmic ray detected in 1991 that possessed 320 EeV of energy.
When ultra-high energy cosmic rays hit Earth’s atmosphere, they cause a cascade of secondary particles and electromagnetic radiation in what is known as an extended air shower.
Some charged particles in the air shower travel faster than the speed of light, producing a type of electromagnetic radiation that can be detected by specialized instruments.
One such instrument is the Telescope Array Observatory in Utah, USA, which found the Amaterasu particle.
This mysterious event seemed to arise from the Local Void, an empty region at the edge of the Milky Way Galaxy.
The experts suggest this could indicate a much larger magnetic deflection than predicted, an unidentified source in the local void, or an incomplete understanding of the physics of high-energy particles.
Professor Matthews said: ‘The particles have such high energy that they should not be affected by galactic and extragalactic magnetic fields.
‘You should be able to point in the air where they come from.
“But in the case of the Oh-My-God particle and this new particle, you trace its trajectory to its source and there is nothing with enough energy to have produced it.
“That’s the mystery of this – what the hell is going on?”
They hope the Amaterasu particle will pave the way for further research that could shed light on ultra-high-energy cosmic rays and where they come from.
John Belz, a professor at the University of Utah’s department of physics and astronomy, said, “It seems like these events are coming from completely different places in the sky.
‘It’s not that there is one mysterious source.
‘They could be defects in the structure of spacetime, clashing cosmic strings.
“I mean, I just spit out crazy ideas that people come up with because there’s no conventional explanation for them.”
The telescope array is a observatory on land that covers about 700 square miles of desert in Utah.
UHECRs only occur about once per century per square kilometer, so an instrument of this size is needed to detect even one.
The research appeared in the journal on Thursday Science.
