Consumer Devices with CMOS camera image sensors
as Pocket-Sized Particle Detectors

Soramame: A Cosmic Ray Observation App for iOS and Android

Cosmic rays are important targets of observation that can provide insights into the origins of the universe and high-energy astrophysical phenomena. Traditionally, their detection has required specialized and expensive equipment. Focusing on the characteristics of CMOS image sensors installed in smartphones and tablets, we developed the app “Soramame”, which enables simplified cosmic ray detection using general consumer devices.

When high-energy charged particles from space strike the CMOS sensor, they generate tiny amounts of electrical charge. The Soramame app captures these signals as images and visualizes them in real time. The detected data is also transmitted to a cloud server, allowing users to view events detected by others via a shared web platform.

Because Soramame allows cosmic ray detection without specialized equipment, it is highly suitable for educational use. Since detection relies on rare and spontaneous events, long-term observation is important. We encourage the use of unused smartphones or tablets to enable continuous data collection.

From an educational perspective, the ability to detect and observe invisible cosmic rays with one's own hands deepens understanding of physical phenomena and fosters scientific curiosity. By altering conditions such as altitude, shielding, and time of day, students can collect and compare data, making the app suitable for inquiry-based learning and data-driven science education.

The app also includes a data sharing feature, allowing users to compare observations from different regions. This enables collaborative learning and supports citizen science activities. In the future, we plan to enhance detection accuracy, integrate more closely with educational curricula, and improve data analysis features to further increase the app's educational value.

Soramame is developed by the Hibino Laboratory, Department of Applied Physics, Faculty of Engineering, Kanagawa University. We hope it will serve as a tool that bridges research and education, and that it helps deepen public understanding and interest in science.

• Latest candidate images (Real time)
• Install App (iOS)
• Install App (Android)

Repurposing Unused Smartphones for Scientific Exploration

Globally, there are now over 19 billion internet-connected devices, including tablets, laptops, and smartphones. With new models released nearly every year, many devices are replaced within just a few years. But what happens to these devices once they are no longer in everyday use?

Despite their compact size, these devices are highly advanced computers, equipped with a range of valuable components. One of the most important is the camera sensor—found in nearly all smartphones and tablets. This silicon-based semiconductor, known as a CMOS image sensor, plays a key role in the development of the Soramame cosmic ray detection app.

Why not breathe new life into an old smartphone or tablet by using it for scientific discovery? With Soramame, you can contribute to cosmic ray observation and turn an unused device into a tool for space science exploration.

Android

iOS

Toward a Global Observation of Cosmic Rays Using 19 Billion CMOS Sensors Worldwide

Among cosmic rays, there exist particles with extremely high energies that far exceed what can be achieved by human-made accelerators on Earth. The most energetic cosmic rays are believed to possess energies over ten million times greater than those generated by artificial accelerators—an energy scale that remains one of the greatest unsolved mysteries in modern physics. How such particles are accelerated and where they originate are still open questions.

These ultra-high-energy cosmic rays are exceptionally rare, making their observation extremely challenging. Moreover, the installation and operation of detection equipment requires significant financial and technical resources. Nonetheless, researchers around the world continue to tackle this mystery through observation and data analysis. Multiple large-scale international collaborative projects are currently underway, deploying numerous detectors across vast areas measuring thousands of square meters to continuously monitor incoming particles from space.

To investigate the origin of cosmic rays, it is crucial to measure their arrival directions. However, in many cases, no prominent astronomical sources are found in the observed directions. This is because cosmic rays are charged particles, and their trajectories are bent by magnetic fields present throughout space, making it difficult to trace them back directly to their point of origin.

For this reason, determining the type of particle—specifically its electric charge—is of great importance. While it has long been believed that most cosmic rays consist primarily of protons (hydrogen nuclei), recent studies suggest that heavier nuclei, such as iron, may also be responsible for some events.

When cosmic rays enter the Earth's atmosphere, they collide with atmospheric nuclei such as nitrogen and oxygen, initiating a phenomenon known as an "air shower"—a cascade of secondary particles. These secondary particles are detected at ground level, and by analyzing their types and densities, researchers attempt to estimate whether the primary cosmic ray was a proton or a heavier nucleus.

At present, there have been very few attempts to observe air showers using CMOS image sensors, which are commonly used in cameras. The main reasons are the small area and thinness of CMOS sensors, as well as the difficulty in estimating the energy of the detected particles. However, we propose that CMOS sensors may offer new possibilities for observing the “core region” of air showers—a zone of particularly high particle density that is often difficult to measure using conventional detectors. Due to their small size and thinness, CMOS sensors are actually well-suited for capturing such high-density regions.

Furthermore, CMOS sensors may be capable of detecting low-energy charged particles that were previously considered as noise. This could enable high-resolution observation of subtle variations in particle density within air showers.

We are currently working to establish a completely new method for cosmic ray air shower observation using CMOS sensors. Through this endeavor, we aim to take on the challenge of uncovering the true nature of cosmic rays.

Updated: April 30, 2025

Contact: Wakiko Takano（r201970105fg_at_jindai.jp）
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