GRAPES-3 experiment, conducted in Ooty, India discovered a new feature in the cosmic-ray proton spectrum. Read the article below for further details.
In a pioneering finding, the GRAPES-3 experiment conducted in GRAPES-3 observatory Ooty, India has uncovered a surprising new feature in the cosmic-ray proton energy spectrum.
This landmark discovery has the potential to reshape our understanding of cosmic ray sources, acceleration mechanisms, and how these ultra-energetic particles propagate throughout the Milky Way galaxy.
What are Cosmic Rays?
Cosmic rays are subatomic particles that constantly bombard the Earth from all directions in space.
First discovered over a century ago, they represent some of the most energetic particles in the known universe.
- They consist primarily of protons and atomic nuclei but also include electrons and positrons.
- These particles can have energies ranging from a few million electron volts (MeV) to over 10^20 electron volts (eV), making some of them the most energetic particles known in the universe.
- The study of cosmic rays is a crucial aspect of astrophysics, as it helps scientists understand the most energetic processes and objects in the cosmos, including supernovae, black holes, and possibly the remnants of the Big Bang.
Cosmic rays are believed to originate from various sources both within our galaxy, the Milky Way, and beyond (extragalactic). The sources include:
- Supernova Remnants: The shock waves from supernovae (the explosive deaths of stars) are thought to be responsible for accelerating the majority of galactic cosmic rays.
- Active Galactic Nuclei: Supermassive black holes at the centres of galaxies can emit jets of charged particles at high energies.
- Pulsars: Highly magnetized, rotating neutron stars can also accelerate particles to high energies.
- Gamma-Ray Bursts: These are extremely energetic explosions observed in distant galaxies, thought to be associated with the collapse of massive stars or the merging of neutron stars.
Importance of Studying Cosmic Rays
Let’s understand the importance of studying cosmic rays:
- When cosmic rays collide with Earth’s atmosphere, they create showers of secondary particles like electrons, photons, muons, protons, and neutrons.
- Scientists study these particle showers to learn about the original cosmic rays that caused them.
- This helps unveil the secrets of where cosmic rays come from, how they gain such immense energy, and how they travel across vast cosmic distances.
- There is ongoing research into the effects of cosmic rays on biological tissues, especially for astronauts on long-duration space missions outside the protective shield of the Earth’s magnetic field and atmosphere.
About the GRAPES-3 Experiment
Details of the GRAPES-3 Experiment are as follows:
- GRAPES-3 stands for Gamma Ray Astronomy PeV EnergieS phase-3. It is a major scientific experiment observatory located in Ooty, India, at an altitude of 2200 meters.
- It is operated by the renowned Tata Institute of Fundamental Research in Mumbai.
- GRAPES-3 uses advanced particle detectors and sensors to precisely measure cosmic rays and study their properties.
Objectives of GRAPES-3 Experiment
Objectives of the GRAPES-3 Experiment are:
- The key objectives of GRAPES-3 are to investigate the origin, acceleration, and propagation of cosmic rays above 10^14 electronvolts (eV) within our galaxy and beyond.
- Confirm the existence of the “knee” – a strange change in the energy pattern of cosmic rays around 3-5 peta-electronvolts (10^15 eV).
- Study the production and acceleration of the highest energy cosmic rays in the universe, around 10^20 electronvolts.
- Perform advanced gamma-ray astronomy of neutron stars, black holes, and other exotic cosmic objects in the multi-TeV energy range.
The Discovery
Recently, GRAPES-3 scientists made an amazing discovery about cosmic rays.
- In their latest finding, the GRAPES-3 collaboration has reported the discovery of an anomalous feature in the cosmic-ray proton energy spectrum at around 166 tera-electronvolt (TeV) or 10^14 eV.
- This was observed while thoroughly mapping the proton spectrum over an energy range spanning 50 TeV to just over 1 peta-electronvolt (PeV) or 10^15 eV.
- Typically, the cosmic ray energy spectrum follows a smoothly declining power law distribution as the energy increases.
However, the newly spotted feature differs from this conventional single power-law model, hinting at underlying processes that have been overlooked until now.
Significance of the Finding
Cosmic rays normally follow a smooth, predictable pattern of decreasing intensity as their energy increases, like a sloping line on a graph.
- However, the newly found feature shows a deviation from this standard pattern, hinting at unknown processes influencing cosmic rays.
- This irregularity lies above 100 TeV but below the well-known “knee” region around 3-5 PeV, making it highly significant.
- The knee has been the focus of intense research for decades, as scientists have sought to understand if it represents a transition between different populations of cosmic ray sources or indicates changing acceleration and propagation dynamics.
Implications and Analysis
This discovery means that the scientific community needs to re-evaluate their current models and theories about cosmic rays.
- Existing ideas may be incomplete in explaining the production of cosmic rays, how they gain tremendous energies, and what happens during their long journey through the galaxy.
- Cosmic rays at these ultra-high energies likely originate from violent cosmic events like supernova explosions and environments around neutron stars and black holes.
- The particles gain tremendous energies through mechanisms like shock acceleration in the expanding debris clouds from supernovae or the extreme electromagnetic fields and jet outflows around spinning neutron stars and black holes.
- As cosmic rays traverse through the turbulent interstellar medium within galaxies, they can undergo significant interactions with magnetic fields and clouds of gas and dust.
- These can alter their energies and trajectories in complex ways.
The GRAPES-3 discovery suggests that current theoretical models may be incomplete in accounting for all the relevant astrophysical processes that shape the cosmic-ray energy spectrum as observed on Earth.
According to the GRAPES-3 researchers, their findings necessitate a comprehensive re-examination of our understanding of cosmic ray sources, the efficiency of their acceleration mechanisms, as well as the roles played by magnetic field configurations and interactions with the interstellar medium during the particles’ galactic propagation.
Also read: Life Cycle of a Star
Way Forward
Incorporating GRAPES-3 data into current models may provide important new insights into specific local phenomena or processes happening across the entire galaxy.
It may help pinpoint specific local phenomena or source populations that contribute to the observed spectral feature.
Alternatively, it could reveal more universal processes at play on a galactic scale that the current theoretical framework has not accounted for sufficiently.
More research from GRAPES-3, other cosmic ray observatories, and multi-messenger astronomy (combining data from cosmic rays, gamma rays, neutrinos, and gravitational waves) is awaited.
Complementary multi-messenger observations combining cosmic, gamma, neutrinos, and gravitational waves could shed further light on the astrophysical engines producing these extremely energetic particles.
Conclusion
As scientists get deeper into unravelling the mysteries highlighted by the GRAPES-3 discovery, we move closer toward an advanced comprehension of the high-energy processes that sculpt our dynamic, particle-bathed universe.
The epic journey of cosmic ray research, which has spanned more than a century since its inception, takes an electrifying new turn with this landmark finding from the highlands of southern India.
Related Articles:
- Square Kilometer Array Observatory
- Major Atmospheric Cherenkov Experiment Telescope (MACE)
- Gamma-ray Bursts (GRBs)
- South Atlantic Anomaly
Article Written By: Priti Raj
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