Got a smartphone? Then you could be part of the largest telescope in the world, a planet-sized detector of cosmic rays that may help find out where in the universe they're coming from.

Two physicists at the University of California say they've created an app that could allow a million smartphone cameras to act together as a global scientific instrument.

High-energy cosmic rays, when they strike the Earth's atmosphere, can cause showers of other particles, but cosmic rays at such high energies are rare, making it hard to pinpoint where they originated in the universe

Michael Mulhearn at UC Davis and Daniel Whiteson of UC Irvine have led a team developing a smartphone app to detect these showers of particles.

Dubbed CRAYFIS, for Cosmic Rays Found in Smartphones, the app uses silicon-based sensors found in smartphone cameras that gather visible light and convert it into an image for your phone's screen.

The camera technology can also by used to detect high-energy particles, the researchers say, and their app records when a phone's camera senses them, and at what level, location and time.

"Whole square kilometers can be drenched in these particles for a few milliseconds," says Whiteson. "The mystery is nobody knows where these crazy, high-energy particles are coming from or what's making them so energetic. But they can be captured by technology in smartphones' cameras."

The CRAYFIS app, available for Android and iOS phones and tablets, runs automatically only when the phone is charging, so it won't impact battery life.

It will upload cosmic ray captures to a University of California server when the phone is connected to WiFi, its developers say.

To preserve a user's privacy, the app will know the difference between particle shower records and a user's photos and will never upload actual images, they say.

A thousand active smartphones covering a square kilometer could detect high-energy cosmic rays striking the atmosphere above them and the subsequent particle showers with efficiency, they say.

If sufficient devices get connected it would create a networked, global detector rivaling or exceeding the capabilities of huge, existing dedicated cosmic ray experiments, they say.

The researchers say they hope to create a user base of one million phones.

As an incentive for smartphone owners to participate, the UC team says if your data gathered by the app is used in subsequent analysis, you'll be listed as an author in a published paper.

Development of the app has taken nearly a year, the researchers said.