Astronomers have detected one of the most powerful cosmic rays ever observed – and it was beamed at Earth from a mysterious part of deep space.
The cosmic phenomenon carried the 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.
As well as being one of the most powerful cosmic rays ever observed, Amaterasu may have originated from an invisible corridor, or ‘void… in the universe’.
Scientists used the Telescope Array in Utah to track the ultrahigh-energy cosmic ray’s direction by recording which detectors lit up and in what order. The problem is they still don’t know where it came from
Cosmic rays are or clusters of tiny, high-energy particles that move through space at nearly the speed of light.
They are frequently detected by instruments on earth and are commonly the result of solar flares or explosions on the sun.
But scientists say Amaterasu could only have been borne out of the most powerful of 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 this ultra-high-energy cosmic ray, I thought there must have been a mistake, as it showed an energy level unprecedented in the last three decades.
‘No promising astronomical object matching the direction from which the cosmic ray arrived has been identified, suggesting possibilities of unknown astronomical phenomena and novel physical origins beyond the Standard Model.’
John Matthews, a research professor at University of Utah’s department of physics and astronomy in the US, said: ‘Things that people think of as energetic, like supernova, are nowhere near energetic enough for this.
‘You need huge amounts of energy, really high magnetic fields to confine the particle while it gets accelerated.’
At 240 quintillion electron volts (EeV), Amaterasu particle has an energy second only to the Oh-My-God particle, another ultra-high-energy cosmic ray which was detected in 1991, possessing 320 EeV of energy.
When ultra-high-energy cosmic rays hit Earth’s atmosphere, they initiate a cascade of secondary particles and electromagnetic radiation in what is known as an extensive 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 specialised instruments.
One such instrument is the Telescope Array observatory in Utah, US, which found the Amaterasu particle.
This mysterious event appeared to emerge from the Local Void, an empty area of space bordering 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 high-energy particle physics.
Professor Matthews said: ‘The particles are so high energy, they shouldn’t be affected by galactic and extra-galactic magnetic fields.
‘You should be able to point to where they come from in the sky.
‘But in the case of the Oh-My-God particle and this new particle, you trace its trajectory to its source and there’s nothing high energy enough to have produced it.
‘That’s the mystery of this – what the heck is going on?’
They hope that the Amaterasu particle will pave the way for further investigations that could help shed light on ultra high-energy cosmic rays and where the come from.
John Belz, a professor at University of Utah’s department of physics and astronomy, said: ‘These events seem like they’re coming from completely different places in the sky.
‘It’s not like there’s one mysterious source.
‘It could be defects in the structure of spacetime, colliding cosmic strings.
‘I mean, I’m just spit-balling crazy ideas that people are coming up with because there’s not a conventional explanation.’
The Telescope Array is a land-based observatory that covers about 700 square kilometers of desert in Utah.
UHECRs only fall about once per century per square kilometer, so it takes an instrument this big to detect even one.
The study appeared on Thursday in the journal Science.
