What is the GRAPES-3 experiment?

About GRAPES-3 experiment: 

• Gamma Ray Astronomy PeV EnergieS phase-3 (GRAPES-3) is designed to studycosmic rays with an array of air shower detectors and a large area muon detector.
• Location: It is located in Ooty, India.
• It is operated by the Tata Institute of Fundamental Research.
• It aims to probe acceleration of cosmic rays in different astrophysical settings.
• Its objectives are to study

o The origin, acceleration and propagation of >1014 eV cosmic rays in the galaxy and beyond.

o Existence of “Knee” in the energy spectrum of cosmic rays.

o  Production and/or acceleration of highest energy (~1020 eV) cosmic rays in the universe.

o Astronomy of multi-TeV γ-rays from neutron stars and other compact object.

o Sun the closest astrophysical object, accelerator of energetic particles and its effects on the Earth.

Key facts about Cosmic rays

• These rays were discovered more than a century ago.
• They are considered to be the most energetic particles in the universe.
• Our planet is constantly bombarded by them from outer space almost uniformly from all directions at a constant rate.
• They enter into Earth's atmosphere and induce a shower of particles that travel to the ground almost at the speed of light.
• The shower particles constitute electrons, photons, muons, protons, neutrons etc.
• They have been observed over a remarkably wide energy range (108 to 1020 eV). 

Q1: What are Muons?

Muons are subatomic particles raining from space. The muon was discovered as a constituent of cosmic-ray particle “showers” in 1936 by the American physicists Carl D. Andersonand Seth Neddermeyer. They are created when the particles in Earth’s atmosphere collide with cosmic rays — clusters of high-energy particles that move through space at just below the speed of light.

Source:A new kink in the proton spectrum to enhance our knowledge of cosmic ray origin