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A star is torn to shreds after approaching a black hole. Scientists have detected for the first time a neutrino – the “ghost particle” – of such an event.
DESY, Scientific communication laboratory
On October 1, 2019, Earth was struck by an invisible, high-energy cosmic ball traveling at almost the speed of light. Billions of these intergalactic bullets pass through our bodies every second without our even knowing it, there is therefore no great concern for the planet. But this particular projectile was special. Deep in the world, the ghostly particle has met its end after colliding with an ice molecule. Fortunately, it did so right next to an extremely sensitive detector built into the South Pole.
The detection triggered an intergalactic hunt for the Celestial Gunner. What had fired the bullet?
In new research, published Monday in the journal Nature Astronomy, scientists detail the detection of a subatomic particle – known as a neutrino – at the IceCube Neutrino Observatory in Antarctica. Using data from the Zwicky Transient Facility at California’s Palomar Observatory, researchers were able to trace the origins of the subatomic bullet to an extreme event around 700 million years ago: the cataclysmic destruction of a star as she was torn apart by a black hole.
This is the first time that such an event has been linked to a detection of neutrinos.
Neutrinos are often described as “ghost particles” because they have no electric charge and have extremely small masses. Like light, they travel essentially in a straight line from their destination. Other charged particles are at the mercy of magnetic fields, but neutrinos only traverse the cosmos unimpeded. We know that they are pouring out of the sun’s core in enormous quantities, and on Earth we can create them in nuclear reactors and particle accelerators.
In April 2019, the Zwicky installation detected a bright glow around a black hole about 700 million light years away. The burst of light was produced when a star moved too close to the black hole, which is about 30 million times more massive than the sun. The immense gravity of the black hole stretched the star and finally it has been spaghetti, torn apart by extreme forces. This is known as a “tidal disturbance event” or TDE.
The star’s violent end is a bright start for astronomers. They were able to link the TDE to the detection of the neutrino by IceCube. Researchers theorize that TDE threw around half of the shattered star into space while the rest settled around the black hole in a gigantic “accretion disk” of hot dust, gas and debris. and shiny. The wild energies around the black hole in the disk cause huge jets of matter to be thrown out of the system. These jets can last for hundreds of days and could explain the small amount of time between the sight of the TDE and the detection of the neutrino at IceCube.
Astrophysicists explain that this shows the existence of a “central motor” which functions as a Natural particle accelerator and can create high energy neutrinos, some of which can collide with Earth.
“The neutrino appeared relatively late, six months after the start of the Star Festival,” said Walter Winter, theoretical astrophysicist of the German electron synchrotron, or DESY. “Our model explains this timing naturally.”
Winter and her co-author Cecilia Lunardini published their modeling in the same issue of Nature Astronomy on Monday.
This is what the accretion disk looks like around a supermassive black hole. The jets flow from the central black hole. The light above the black hole is actually on the opposite side of the hole – the black hole bends space-time to make it appear as if it is surrounded by light.
DESY, Scientific communication laboratory
The discovery of a neutrino emanating from a TDE is a breakthrough for astronomers who hope to understand the universe in a new way. Scientists could only trace a neutrino to its source once before. It was IceCube who also made this detection. In 2017, researchers from the observatory detected the revealing signature of a neutrino and alerted astronomers to the phenomenon. Telescopes were able to trace the source of the neutrino to a distant galaxy that housed a “blazar” – a huge black hole surrounded by an accretion disk with a directed jet directly at the observer.
The two detections both show that black holes are intergalactic guns, shooting ghost particles from deep space across the universe. It could help astronomers better understand the processes that occur near a black hole, and could even begin to solve a mystery that has haunted astrophysics since the 1960s: where the very high-energy cosmic rays come from. sometimes crash into the earth’s atmosphere?
Researchers have detected a number of TDEs since the Zwicky transient facility began surveying the sky, and in the future, more sensitive telescopes may be able to further link these high-energy particles to events. IceCube will also be essential in improving our understanding. The observatory is expected to be upgraded during the 2022 and 2023 Antarctic seasons, notwithstanding the pandemic, which is expected to increase the number of neutrino detections by 10 times.
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