Physicists have detected the highest-energy light ever recorded, coming from the Crab Nebula, the remains of a supernova, around 6,500 light years from the Earth.
Researchers in Tibet used enormous detectors to pick out the particle showers created by these gamma rays as they hit particles in the Earth’s atmosphere.
With energies of 100–450 trillion electron volts, the photons are around 69 times more energetic than the highest-powered particles in the Large Hadron Collider.
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Physicists have detected the highest-energy light ever recorded, coming from the remains of a supernova — the Crab Nebula, pictured — that lies around 6,500 light years from the Earth
The high-energy gamma ray photons from the Crab Nebula were detected using the Tibet AS-gamma experiment, a so-called air shower observation array based in Yangbajain, in western China.
The experiment uses nearly 600 particle detectors, distributed over around 700,000 square feet (65,000 square metres) to detect the particle showers created when the high-energy photons hit Earth’s atmosphere.
Each of the photons they detected had energies in excess of 100 trillion electron volts, the previously-detected record, with some as high as 4.5 times that.
For comparison, visible light photons have energies of around a few electron volts, while the Large Hadron Collider — the most powerful particle accelerator built by man — can only reach energies of around 6.5 trillion electron volts.
Located around 6,500 light years away, the Crab Nebula was formed after a star exploded in a supernova that was spotted by Chinese astronomers in 1054.
This explosion created the conditions that can generate extremely high-energy photons.
First, charged particles like electrons were driven up to high energies by the shock-wave and the magnetic forces generated by the supernova explosion.
When these high-energy electrons in the Crab Nebula collide with low-energy photons, they transfer their energy, making the photons high-energy instead.
These photons travel off through space and some may even arrive at the Earth.
When one of these high-energy photons interacts with particles in the Earth’s atmosphere, they create showers of other subatomic particles — electrons and positrons — which can be detected by instruments located on the Earth’s surface.
The challenge, however, is to distinguish the particle showers caused by high energy photons hitting the atmosphere with those that are also created by cosmic rays, which are much more common.
Researchers in Tibet used enormous detectors to pick out the particle showers created by these gamma rays from the Crab Nebula, pictured, as they hit the Earth’s atmosphere
To do this, experts used underground detectors to exclude any event that created muons — elementary particle that are essentially the heavier relatives of electrons — as these particles are created in showers from cosmic rays but not photons.
After ruling out as many of the muon-generating shower events as they could, researchers were left with 24 particle showers, detected across a 3-year-period, that may have been triggered by photons with energies above 100 trillion electron volts.
Some of the shower events even appeared to have been triggered by photons with energies in excess of 450 trillion electron volts.
The researchers do caution that six of the events they detected could have potentially been caused by cosmic rays, rather than high-energy photons, due to uncertainties in the muon-based exclusion process.
‘This energy regime has not been accessible before,’ astrophysicist Petra Huentemeyer of the Michigan Technological University in Houghton, who was not involved in the study, told Science News.
‘It’s an exciting time’ for physicists who study gamma rays, she added.
By searching for photons with even higher energies, researchers could find out exactly how the particles are given their energy boosts.
‘There has to be a limit to how high the energy of the photons can go,’ said physicist David Hanna of McGill University, Montreal, who was also not involved in this study.
Determining this maximum possible energy would allow experts to refine their theories.
The full findings of the study have been accepted for publication in the journal Physical Review Letters.
WHAT IS A SUPERNOVA AND HOW DOES IT FORM?
A supernova occurs when a star explodes, shooting debris and particles into space.
A supernova burns for only a short period of time, but it can tell scientists a lot about how the universe began.
One kind of supernova has shown scientists that we live in an expanding universe, one that is growing at an ever increasing rate.
Scientists have also determined that supernovas play a key role in distributing elements throughout the universe.
In 1987, astronomers spotted a ‘titanic supernova’ in a nearby galaxy blazing with the power of over 100 million suns (pictured)
There are two known types of supernova.
The first type occurs in binary star systems when one of the two stars, a carbon-oxygen white dwarf, steals matter from its companion star.
Eventually, the white dwarf accumulates too much matter, causing the star to explode, resulting in a supernova.
The second type of supernova occurs at the end of a single star’s lifetime.
As the star runs out of nuclear fuel, some of its mass flows into its core.
Eventually, the core is so heavy it can’t stand its own gravitational force and the core collapses, resulting in another giant explosion.
Many elements found on Earth are made in the core of stars and these elements travel on to form new stars, planets and everything else in the universe.
