Astronomers have unveiled a novel approach to examine the energetic particles that incessantly strike Earth from the cosmos, known as cosmic rays. This innovative technique suggests a comprehensive analysis of the cascades of secondary particles produced when cosmic rays collide with Earth’s atmosphere, serving as a lens to deepen our understanding of these phenomena.
Tracking cosmic rays back to their origins is a challenge because the charged particles that form them are repeatedly deflected by the magnetic fields they encounter while hurtling through space at speeds nearing that of light. This results in their origins, typically situated beyond the Solar System, remaining largely enigmatic.
Potential sources of cosmic rays include supernovae; however, these particles appear too energetic to have originated solely from the explosions of massive stars. Other candidates consist of active galactic nuclei or quasars fueled by voracious supermassive black holes, gammaray bursts, or even unusual dark matter, yet astronomers have not yet uncovered definitive evidence linking them to these sources.
What is clearer is the aftermath when these charged cosmic particles collide with our atmosphere. Upon striking particles in our atmosphere, they generate a vast 'air shower' of secondary particles that descend to Earth’s surface. When thousands, millions, or even billions of these particles reach the ground, this phenomenon is termed an extensive air shower. In a recent study, researchers discovered how meticulous observations of these particle showers, captured by the Subaru Telescope perched atop the Mauna Kea volcano in Hawaii, could reveal more about them and the cosmic rays prompting them.
The luminous trails formed by extensive air showers as they move in front of telescopes can often interfere with astronomical observations, disrupting the view of the Solar System, the Milky Way, and beyond. Nevertheless, the research team opted to regard these beams of light as more than mere 'noise' cluttering their otherwise immaculate data.
The scientists scrutinized approximately 17,000 images taken from 2014 to 2020, identifying 13 images that featured extensive air showers. These images displayed a significantly higher count of particle tracks than anticipated, hinting at a potential method to unravel the enigma of cosmic rays.
"With traditional observational techniques, it’s tough to differentiate between the varieties of particles that make up extensive air showers," remarked team leader and Osaka Metropolitan University scientist Toshihiro Fujii. "Our approach, conversely, possesses the capability to ascertain the nature of individual particles."
Researchers suggest that cosmic rays are predominantly composed of protons, constituting around 90 percent of the atomic nuclei of hydrogen—the lightest element in the universe—alongside nine percent helium nuclei and one percent other particles, which includes electrons and peculiar atomic nuclei as dense as lead.
This new study could provide a superior methodology to uncover the particle composition of air showers, subsequently enhancing our understanding of cosmic rays and aiding in identifying their sources, according to team members. "By amalgamating our method with traditional techniques, we aspire to enrich our comprehension of extensive air showers,"
Fujii concluded. "This strategy may enable us to hunt for dark matter or other exotic particles, thereby granting us further insights into the universe's transition into a matter-dominated epoch."
--Bhautik Thummar
