1,000m underground, Japan's Super-Kamiokande detector - a vast cavern filled with 50,000 tons of ultra-pure water and 13,000 photomultiplier tubes - detects particles originating from supernovae on the other side of the universe...
Mystery particle
Elementary particles are the smallest known building blocks of all matter in the universe. One of these has eluded scientists for decades - the neutrino. While some of its basic characteristics, like its mass, are still a mystery, scientists think it may be the key to unravelling the mysteries of supernovae and the Big Bang, which gave birth to the universe.
Cloud chamber capturing invisible radiationMiraikan – The National Museum of Emerging Science and Innovation
Scientists have long researched the composition of the universe.
This cloud chamber captures radiation and helped facilitate the discovery of elementary particles.
The neutrino’s existence was predicted a long time before being discovered.
Neutrinos from spaceMiraikan – The National Museum of Emerging Science and Innovation
Neutrinos are created in various ways - inside supernovae, in the center of the sun and many were made during the Big Bang - at the birth of the universe.
In fact, hundreds of trillions of neutrinos pass through our bodies every second.
The neutrino is nicknamed the ‘ghost particle’ because it rarely reacts with other particles, and is so hard to catch.
The beginning of the universe and its historyMiraikan – The National Museum of Emerging Science and Innovation
Scientists think that if they can trap ghost particles they may reveal new insights into some of the mysteries of the universe and of elementary particles, such as how the universe came into existence.
Seeing ghosts
The Super-Kamiokande is a particle detector built to observe ghost particles - neutrinos. Built in 1996, the 40-meter tank incorporates the latest technology and scientific knowledge.
Overall sketch of Super-Kamiokande (1996)Miraikan – The National Museum of Emerging Science and Innovation
Neutrinos rarely react with other substances.
But to increase the chances of detecting one, the Super-Kamiokande tank is filled with 50,000 tons of ultra-pure water, inside the Kamioka mine in Gifu, Japan.
Photomultiplier tubes lined up inside the tank (Miraikan exhibition)Miraikan – The National Museum of Emerging Science and Innovation
When water molecules react with neutrinos, a weak light is created known as ‘Cherenkov light’.
The Super-Kamiokande detector senses the presence of neutrinos using a photomultiplier tube installed in the walls of the detector.
Photomultiplier tube (1981) by Hamamatsu Photonics K.K.Miraikan – The National Museum of Emerging Science and Innovation
When water molecules react with neutrinos, the photomultiplier tube converts the photon particles released by the reaction.
This photomultiplier tube is the largest and very sensitive in the world - enabling very high-precision measurements.
Internal photograph of Super-Kamiokande (1996)Miraikan – The National Museum of Emerging Science and Innovation
The tube has 11129 light sensors at 70cm intervals, each tuned to detect Cherenkov light.
Data observed by Super-Kamiokande (1996)Miraikan – The National Museum of Emerging Science and Innovation
Cherenkov light is released in a conical shape from the point at which water molecules react with neutrinos, creating a circular mark on the walls of the detector.
The strength and timing of the marking tell scientists what kind of particle was released, and in which direction.
Permanent Exhibition of Miraikan "Neutrino Observations"Miraikan – The National Museum of Emerging Science and Innovation
This exhibition shows the Super-Kamiokande at 1/10 scale, and demonstrates how Cherenkov light hits the wall.
Super-KamiokandeMiraikan – The National Museum of Emerging Science and Innovation
Two major discoveries have been made using the detector, which have sent shockwaves through the physics community.
Each of these discoveries was awarded a Nobel prize.
Dr. Masatoshi KoshibaMiraikan – The National Museum of Emerging Science and Innovation
Dr. Masatoshi Koshiba
Creator of the Super-Kamiokande, Dr. Koshiba succeeded in capturing a neutrino using the predecessor to the Super Kamiokande, the Kamiokande.
In doing so, he won the Nobel prize in physics.
170,000 years ago, inside the Large Magellanic Cloud - a galaxy near the Milky Way - a supernova took place.
This generated a large number of neutrinos that were sent hurtling out into space.
Some of these reached Earth in February 1987, and 11 of them were captured by Kamiokande.
Dr. Takaaki KajitaMiraikan – The National Museum of Emerging Science and Innovation
Dr. Takaaki Kajita
Dr. Kajita studied atmospheric neutrinos born in collisions between cosmic rays and the atmosphere using the Super-Kamiokande, and received the Nobel Prize in Physics.
The research team that Dr Kajita led proved the fact that atmosphere neutrinos oscillate for the first time.
The fact that the neutrino spins indicates that its properties change periodically. In other words, it means that the neutrino has mass.
It is a phenomenon which cannot be explained by the knowledge of physics so far.
At the end of the universeMiraikan – The National Museum of Emerging Science and Innovation
The Super-Kamiokande has already helped answer big questions about the universe.
As research progresses, further mysteries surrounding the beginnings of the universe and the origins of life may eventually be unraveled.
Miraikan CafeMiraikan – The National Museum of Emerging Science and Innovation
However, there are still many mysteries yet to be elucidated.
By uncovering the mysteries of the universe, the understanding of this world and ourselves will gradually deepen, leading to the development of new discoveries and technologies.
Miraikan － The National Museum of Emerging Science and Innovation
Kamioka Observatory, ICRR(Institute for Cosmic Ray Research), The University of Tokyo
NASA
NASA/JPL-Caltech/University of Wisconsin
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