This article explores how scientists captured an image of the sun at night using neutrinos detected by the Super-Kamiokande detector in Japan. It explains what neutrinos are, their elusive nature, how they travel through the sun and Earth, and the significance of detecting them for understanding solar processes and fundamental physics.
There is a fascinating image circulating on the internet that shows the sun seemingly captured at night. This might sound impossible at first—how can the sun be photographed at night on Earth? The answer lies not in visible light, but in detecting elusive particles called neutrinos.
The image was taken not with visible light, infrared, or any form of electromagnetic radiation, but through detecting neutrinos emitted by the sun. These particles can pass through the Earth and everything on it almost undisturbed, making it possible to detect the sun’s presence even when it is not visible in the sky.
Neutrinos are subatomic particles that are incredibly elusive. They interact very weakly with matter, which is why they are often called "ghost particles." Approximately 100 billion solar neutrinos pass through your thumbnail every second without you noticing.
Unlike photons (light particles), neutrinos barely interact with matter because they have very little mass—at least a million times less than an electron. In fact, it was only in 1998 that scientists discovered neutrinos have a tiny mass, a finding that won the Nobel Prize in 2015.
Neutrinos interact only with two of the four fundamental forces: gravity and the electroweak force. They do not interact with the electromagnetic or strong nuclear forces, which contributes to their ghostly nature.
Light produced in the core of the sun takes hundreds of thousands of years to reach the surface because it constantly interacts with dense matter inside the sun, bouncing around before escaping. After that, it takes about 8 minutes to travel from the sun’s surface to Earth.
Neutrinos, however, interact so little with matter that they escape the sun’s core almost immediately, taking only about 2.3 seconds to reach the surface and then 8 minutes to reach Earth. This means neutrinos provide a much more immediate signal of processes happening inside the sun.
The image of the sun at night was created using data from the Super-Kamiokande detector in Japan, a giant cylindrical tank about 40 meters by 40 meters filled with 50,000 tons of ultra-pure water and lined with sensitive light detectors.
When a neutrino interacts with an electron in the water, it produces a tiny flash of light. The detectors capture these flashes, allowing scientists to infer the direction and energy of the incoming neutrinos.
Despite trillions of neutrinos passing through every second, only about 30 neutrinos are detected each day due to their weak interactions. To create the image, scientists collected data over approximately 500 days, mostly underground about a kilometer deep to shield the detector from other particles.
Neutrinos provide a unique window into the sun’s core and other astrophysical phenomena. Because they escape the sun almost instantly, they can serve as an early warning system for solar events, such as solar flares or other catastrophic changes.
Moreover, studying neutrinos helps physicists explore fundamental questions about the universe, such as:
These questions remain open and are at the forefront of modern physics research.
The image created from neutrino detections dates back to the 1990s and represents a significant achievement in particle physics and astrophysics. It demonstrates the incredible sensitivity of detectors like Super-Kamiokande and the potential of neutrino astronomy.
Capturing an image of the sun at night using neutrinos is a remarkable feat that highlights the mysterious and fascinating nature of these ghostly particles. Neutrinos not only allow us to see the sun in a new way but also open doors to understanding the fundamental workings of the universe. As research continues, neutrinos may reveal even more secrets about the cosmos and the forces that govern it.
This breakthrough marks an exciting return to physics exploration and reminds us of the vast unknowns still waiting to be uncovered in the universe.
