GRAPES-3 experiment

• Researchers at GRAPES-3 have identified a distinctive characteristic in the cosmic-ray proton spectrum, particularly at an energy level of approximately 166 tera-electron-volt (TeV).
• This revelation spans a measurement range from 50 TeV to slightly over one peta-electron-volt (PeV), sparking potential shifts in our comprehension of cosmic ray origins, their acceleration processes, and their movement within the Milky Way.

ABOUT COSMIC RAYS

• Cosmic rays, first discovered over a century ago, constitute the most energetic particles in the universe.
• These particles uniformly bombard Earth from all directions, penetrating the atmosphere and generating a cascade of secondary particles such as electrons, photons, muons, protons, and neutrons, which reach the ground at nearly light speed.

ABOUT GRAPES-3 EXPERIMENT

• The GRAPES-3 experiment is located at Ooty, Tamil Nadu.
• It started as a collaboration of the Tata Institute of Fundamental Research, Mumbai, India and the Osaka City University, Osaka, Japan.
• At present many institutions from India and Japan are in collaboration.
• GRAPES-3 (Gamma Ray Astronomy PeV EnergieS phase-3) is designed to study cosmic rays with an array of air shower detectors and a large area muon detector.
• It aims to probe acceleration of cosmic rays in the following four astrophysical settings. These include acceleration of particles to,
  • ~100 MeV in atmospheric electric fields through muons,
  • ~10 GeV in Solar system through muons,
  • ~1 PeV in our galaxy through nuclear composition of cosmic rays,
  • ~100 EeV in nearby universe through measurement of diffuse γ-ray flux.

• Objectives of the GRAPES-3 Experiment- Study of
  • The origin, acceleration and propagation of >1014 eV cosmic rays in the galaxy and beyond.
  • Existence of “Knee” in the energy spectrum of cosmic rays.
  • Production and/or acceleration of highest energy (~1020 eV) cosmic rays in the universe.
  • Astronomy of multi-TeV γ-rays from neutron stars and other compact object.
  • Sun the closest astrophysical object, accelerator of energetic particles and its effects on the Earth.