Did you know your smartphone might be good for something besides spamming out duck-lip pics of yourself? Did you know your phone might be a valuable scientific tool to help us understand the cosmos? Are you reading this on your phone right now? Hey! Get off the phone! You could be using this time to collect data on Ultra High Energy Cosmic Rays.
Cosmic rays (a generic term for high energy protons and atomic nuclei) come from the Sun, other stars, galaxies, etc. are constantly pelting our planet.
A lot of these particles get deflected by our magnetosphere, but some have so much energy they make it through and hit our atmosphere. Collisions between cosmic rays and other molecules in our atmosphere result in showers of high energy particles.
Cosmic rays can have energies ranging from 109 eV to 1020 eV, but there are orders of magnitude fewer of the really high energy particles. Ultra High Energy Cosmic Rays (UHECR), those particles with energies above 1018 eV are hard to detect since there are so few and the instruments built to detect them need to be enormous! The Pierre Auger Observatory is an array of detectors in Argentina covers an area of 1,200 mi2
That might sound like a lot of area but it’s really only a tiny Luxembourg-sized fraction of the globe so detection of UHECR are still far and few between. Well, some researchers have an idea that might increase the likelihood of detecting UHECR by using smartphones as distributed detectors.
When a single UHECR hits the atmosphere enormous showers of muons, protons, and electrons rain down on us at nearly the speed of light. This ionizing radiation is actually detectable by the CMOS (complementary metal-oxide semiconductor) sensor that is a part of cameras in smartphones. During normal use these sensors are busy turning visible photons into current through absorption on silicon photodiode pixels (taking pictures)…
but these sensors are good enough though that they can detect higher-energy photons! So right now your phone is picking up any particles from a UHECR collision and all we need to do is collect and track that data.
Luckily, yes, there’s an app for that.
Daniel Whiteson and Michael Mulhearn have developed an app that will tap into your phones CMOS sensor anytime the smartphone is plugged in and camera face down. If the sensor detects a high-energy photon it will tag that particle with your phones geolocation and send that information to the researchers via a wifi connection. It happens without you knowing about it, doesn’t cost you anything and doesn’t even use up battery!
Sounds easy so maybe now you’re wondering why we care about collecting and counting UHECR. First of all, we don’t actually know where it comes from and we don’t really know how it’s made. UHECRs are produced by synchrotron radiation. Synchrotron radiation are the result of energized particles produced when charged particles are accelerated in a curved path at non-relativistic speeds. There are a number of synchrotrons here on Earth…
but there are lots of them out there in space too! Supernovae, active galactic nuclei and gamma-ray bursts might all produce UHECRs but we don’t really know what is accelerating those particles, how these celestial objects are acting like synchrotrons. By counting UHECRs and knowing where in the sky they came from we can unravel the mystery of their formation.
So get off the phone already! Download the app, plug in, and start making science! If Whiteson and Mulhearn can get 1,000 phones per km2 together we can rival the $50 million observatory in Argentina. That might sound like a lot but with 1.5 BILLION phones out there in the world the detectors have been deployed and we just need to record the data.
This is something we can actually do!