23.6 The Mystery of the Gamma-Ray Bursts
3 min read•june 12, 2024
are cosmic explosions that release intense bursts of high-energy radiation. Discovered in the 1960s, these events have captivated astronomers with their immense power and mysterious origins. They come in short and long varieties, each with distinct causes and characteristics.
Scientists now believe stem from the collapse of massive stars or the merger of dense stellar remnants. By studying these fleeting flashes, researchers gain insights into the early universe, star formation, and the deaths of the most massive stars.
Discovery and Characteristics of Gamma-Ray Bursts
Discovery of gamma-ray bursts
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- Gamma-ray bursts (GRBs) first discovered in late 1960s by designed to monitor compliance with Nuclear Test Ban Treaty
- (CGRO) launched in 1991 with (BATSE) onboard detected over 2,700 GRBs
- launched in 1996 provided accurate positions of GRBs enabling follow-up observations at other wavelengths (optical, radio)
- launched in 2004 detects and provides rapid localization of GRBs for follow-up observations
- launched in 2008 provides high-energy gamma-ray observations of GRBs
Beamed energy in bursts
- GRBs emit energy in form of which are narrow beams of energy focused in specific direction ()
- reduces total energy output required to produce observed luminosity as actual energy released is less than if emission were spherical
- Beaming angle affects observed properties of GRBs
- Observers located within beam observe more luminous burst
- Observers outside beam may not detect GRB at all
Physical Processes and Types of Gamma-Ray Bursts
Radiation process and afterglows
- GRBs thought to originate from collapse of massive stars () or merger of compact objects (neutron stars, black holes)
- Initial burst of gamma-rays produced by internal shocks within relativistic jet caused by collisions between shells of material moving at different velocities
- emission occurs as jet interacts with surrounding medium
- External shocks between jet and interstellar medium produce longer-wavelength emission observed in X-ray, optical, and radio wavelengths
- is primary emission mechanism in GRB where electrons spiraling in magnetic fields produce synchrotron emission
Short vs long-duration bursts
- GRBs classified into two main categories based on duration
- last less than 2 seconds
- last more than 2 seconds
- Short-duration GRBs thought to originate from merger of compact objects like binary neutron stars or neutron star and black hole ()
- Long-duration GRBs associated with collapse of massive stars more than 25 times mass of Sun in
- Short and long-duration GRBs differ in host galaxies and locations within galaxies
- Short GRBs found in both old and young stellar populations, often in galaxy outskirts
- Long GRBs typically found in star-forming regions of young, low-metallicity galaxies
Bursts and early universe insights
- GRBs are most luminous events known in universe and can be detected from very high corresponding to early universe
- Long-duration GRBs associated with deaths of massive stars provide insight into star formation rates and metallicity in early universe
- GRBs can be used as probes of as absorption features in GRB afterglow spectra reveal composition and evolution of intergalactic medium
- GRBs may contribute to of universe as high-energy radiation from GRBs could have helped ionize neutral hydrogen in early universe
Multi-messenger astronomy and GRBs
- GRBs play a crucial role in multi-messenger astronomy, combining electromagnetic observations with other forms of information
- from compact object mergers can be detected in conjunction with short GRBs, providing new insights into these events
- GRBs serve as standard candles for measuring cosmic distances, contributing to our understanding of the
Key Terms to Review (33)
Afterglow: Afterglow is the emission that follows a gamma-ray burst (GRB) and can be observed across various wavelengths, including X-rays, optical, and radio. It provides crucial information about the environment surrounding the GRB and the mechanisms driving these powerful cosmic events.
Afterglows: Afterglows refer to the long-lasting, fading emissions of electromagnetic radiation that are observed following the initial, brief bursts of gamma-ray radiation known as gamma-ray bursts (GRBs). These afterglows provide crucial insights into the nature and origins of these enigmatic cosmic events.
Beaming: Beaming, in the context of gamma-ray bursts, refers to the directional emission of intense gamma-ray radiation from a compact source, such as a black hole or a neutron star. This phenomenon is characterized by the focused and highly collimated nature of the gamma-ray beam, which can be observed from Earth as a brief, intense flash of gamma-ray radiation.
BeppoSAX: BeppoSAX was an Italian-Dutch satellite for X-ray astronomy, operational from 1996 to 2002. It significantly contributed to the study of gamma-ray bursts by providing precise locations for these events.
BeppoSAX Satellite: The BeppoSAX satellite was an Italian-Dutch X-ray astronomy mission that made significant contributions to the understanding of gamma-ray bursts, a mysterious and powerful cosmic phenomenon. Launched in 1996, it played a crucial role in the study and observation of these elusive events.
Burst and Transient Source Experiment: The Burst and Transient Source Experiment (BATSE) was a gamma-ray burst detection instrument that was part of the Compton Gamma Ray Observatory (CGRO) satellite. It was designed to study the mysterious phenomenon of gamma-ray bursts, which are brief, intense flashes of high-energy radiation that occur randomly throughout the universe.
Collimated Jets: Collimated jets refer to highly focused, narrow beams of material ejected at high velocities from the vicinity of compact objects, such as black holes or neutron stars. These jets are characterized by their tightly confined, parallel flow of material, which is in contrast to the more diffuse and isotropic outflows observed in other astrophysical phenomena.
Compact Object Mergers: Compact object mergers refer to the collision and fusion of extremely dense celestial bodies, such as neutron stars or black holes, which can produce some of the most energetic and luminous events in the universe, including gravitational waves and gamma-ray bursts.
Compton Gamma-Ray Observatory: The Compton Gamma-Ray Observatory was a major space-based observatory that operated from 1991 to 2000, making groundbreaking observations of gamma-ray sources in the universe. It was launched to study the high-energy processes that produce gamma rays, including the mysterious gamma-ray bursts.
Core-Collapse Supernovae: Core-collapse supernovae are a type of supernova that occur when the core of a massive star collapses under its own gravity, leading to a catastrophic explosion. This process is a crucial part of the life cycle of certain stars and has significant implications for the study of gamma-ray bursts, which are often associated with these events.
Cosmological Distance Scale: The cosmological distance scale is a hierarchical system used to measure distances to astronomical objects, ranging from the nearest stars to the most distant galaxies in the observable universe. It serves as a crucial framework for understanding the large-scale structure and evolution of the cosmos.
Fermi Gamma-ray Space Telescope: The Fermi Gamma-ray Space Telescope is a space observatory launched by NASA in 2008 to study the most energetic and explosive phenomena in the universe, including gamma-ray bursts, active galactic nuclei, and pulsars. It is a powerful tool for exploring the high-energy universe and has made significant contributions to our understanding of various cosmic phenomena.
Gamma-ray burst: A gamma-ray burst (GRB) is an extremely energetic explosion observable in distant galaxies, emitting intense gamma radiation. They are the brightest electromagnetic events known to occur in the universe, lasting from milliseconds to several minutes.
Gamma-ray bursts: Gamma-ray bursts (GRBs) are extremely energetic explosions observed in distant galaxies, emitting intense gamma radiation. They are the brightest electromagnetic events known to occur in the universe.
Gamma-Ray Bursts: Gamma-ray bursts (GRBs) are intense flashes of gamma radiation that occur randomly and briefly in distant regions of the universe. They are the most luminous electromagnetic events known to occur in the universe, releasing as much energy in a few seconds as the Sun does in millions of years.
Gravitational waves: Gravitational waves are ripples in spacetime caused by accelerating massive objects, such as colliding black holes or neutron stars. These waves propagate at the speed of light and carry energy away from their source.
Gravitational Waves: Gravitational waves are disturbances in the fabric of spacetime, caused by the acceleration of massive objects, that propagate outward at the speed of light. These waves are a prediction of Einstein's general theory of relativity and have been observed directly, providing experimental evidence for this fundamental aspect of our understanding of gravity.
Intergalactic Medium: The intergalactic medium (IGM) refers to the diffuse gas and plasma that fills the space between galaxies within a galaxy cluster or the larger-scale structure of the universe. It is the matter that exists outside of galaxies and stars, permeating the vast empty spaces between them.
Long-duration gamma-ray burst: Long-duration gamma-ray bursts (GRBs) are intense bursts of gamma radiation lasting more than two seconds, often associated with the death of massive stars. They are among the most energetic events in the universe, indicating the collapse of a star into a black hole or neutron star.
Long-Duration GRBs: Long-duration gamma-ray bursts (long-duration GRBs) are a class of gamma-ray bursts that last for more than 2 seconds, in contrast to short-duration GRBs which last less than 2 seconds. These long-duration GRBs are thought to be associated with the deaths of massive stars and the formation of black holes.
Progenitor Stars: Progenitor stars are the precursor stars that give rise to certain astronomical phenomena, such as gamma-ray bursts. These stars are massive, short-lived, and often end their lives in dramatic explosions that can produce some of the most energetic events in the universe.
Redshifts: Redshift is a phenomenon in which the wavelength of light from a distant object appears to be shifted towards longer, redder wavelengths. This shift is caused by the expansion of the universe and the Doppler effect, and it provides important information about the properties and dynamics of celestial objects and the universe as a whole.
Reionization: Reionization is a critical phase in the early history of the universe when the neutral hydrogen that permeated the cosmos after the Big Bang was re-ionized, transforming the universe from a neutral, opaque state to a transparent, ionized state. This process had far-reaching implications for the formation and evolution of the first stars, galaxies, and large-scale structures in the universe.
Relativistic Jets: Relativistic jets are narrow, high-speed streams of plasma that are ejected from the vicinity of supermassive black holes at the centers of active galaxies, such as quasars and active galactic nuclei. These jets travel at a significant fraction of the speed of light, exhibiting relativistic effects.
ROTSE: ROTSE, or the Robotic Optical Transient Search Experiment, is a system of telescopes designed to detect optical transients such as gamma-ray bursts (GRBs). It operates autonomously to capture transient phenomena in real-time.
Short-duration gamma-ray burst: Short-duration gamma-ray bursts (SGRBs) are intense bursts of gamma-ray light lasting less than two seconds. They are believed to result from the merger of binary neutron stars or a neutron star and a black hole.
Short-Duration GRBs: Short-duration gamma-ray bursts (short-duration GRBs) are intense flashes of gamma radiation that last less than 2 seconds. They are one of the most energetic and mysterious events in the universe, releasing more energy in a fraction of a second than the Sun will in its entire lifetime.
Swift: Swift is a space telescope launched by NASA in 2004 to detect gamma-ray bursts (GRBs). It is equipped with instruments that allow it to observe and rapidly pinpoint the location of these high-energy events across multiple wavelengths.
Swift Gamma-Ray Burst Mission: The Swift Gamma-Ray Burst Mission is a NASA space observatory dedicated to the study of gamma-ray bursts, which are brief and extremely energetic explosions of light in the universe. It was launched in 2004 and continues to provide valuable data and insights about these mysterious cosmic events.
Synchrotron radiation: Synchrotron radiation is electromagnetic radiation emitted when charged particles travel at near-light speeds in curved paths. This phenomenon is often observed in the magnetospheres of giant planets due to their strong magnetic fields.
Synchrotron Radiation: Synchrotron radiation is a type of electromagnetic radiation emitted by charged particles, typically electrons, when they are accelerated in a curved path by a strong magnetic field. This radiation is observed in various astrophysical phenomena, including gamma-ray bursts, supermassive black holes in quasars, and active galactic nuclei.
Type Ic supernova: A type Ic supernova is a stellar explosion resulting from the collapse of a massive star that has lost its outer layers of hydrogen and helium. These events are significant sources of gamma-ray bursts and heavy elements in the universe.
Vela Satellites: The Vela satellites were a series of American military satellites launched during the Cold War era to detect nuclear explosions in space. They played a crucial role in monitoring compliance with the Partial Nuclear Test Ban Treaty and were instrumental in the discovery of gamma-ray bursts, one of the most energetic and mysterious phenomena in the universe.