ASTROPHYSICAL JETS

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Context

• Scientists have investigated how the composition of plasma affects the dynamics of astrophysical jets, which are outflows of ionized matter emitted as beams from celestial bodies like black holes, neutron stars, and pulsars.

Details

• The exact composition of astrophysical jets is unknown; they may consist of electrons, protons, and/or positrons (positively charged electrons).
• Understanding jet composition is crucial for pinpointing the physical processes occurring near black holes and neutron stars.
• The equation of state (EOS) describes the relationship between thermodynamic quantities like mass density, energy density, and pressure, without considering jet composition.
• A new relativistic EOS, partly proposed by scientists from ARIES, incorporates the composition of relativistic plasma and its impact on jet dynamics

Astrophysical jets

• Astrophysical jets are highly energetic, narrow beams of matter and energy that are ejected from the regions surrounding certain types of astronomical objects, such as black holes, neutron stars, and young stellar objects.
• These jets can travel at speeds close to the speed of light and extend across vast distances in space.

Types of Astrophysical Jets

• Relativistic Jets
  • Origin: Usually associated with black holes in active galactic nuclei (AGN), quasars, and microquasars.
  • Speed: Close to the speed of light.
  • Features: Highly collimated, often exhibit Doppler boosting and relativistic beaming.
• Non-relativistic Jets
  • Origin: Typically found in young stellar objects, protostars, and certain types of binary star systems.
  • Speed: Significantly slower than the speed of light, often a few hundred km/s.
  • Features: Less collimated compared to relativistic jets, can be observed in various wavelengths such as infrared and radio.

Formation Mechanisms

• Accretion Disks
  • Jets are often formed in the regions surrounding accretion disks around black holes, neutron stars, or young stars.
  • Magnetic fields in the accretion disk play a crucial role in launching and collimating the jets.
• Magnetohydrodynamic (MHD) Processes
  • Interaction between the magnetic fields and ionized plasma in the disk.
  • The twisting of magnetic field lines can create a magnetic spring that accelerates particles along the field lines, forming jets.
• Radiation Pressure
  • In some cases, radiation pressure from the central object can help drive the outflow of matter in the form of jets.

Examples of Astrophysical Jets

• Active Galactic Nuclei (AGN) Jets
  • Associated with supermassive black holes at the centers of galaxies.
  • Can extend for thousands to millions of light-years.
  • Example: The jet from the galaxy M87, famously imaged by the Event Horizon Telescope.
• Microquasars
  • Stellar-mass black holes or neutron stars with jets.
  • Example: SS 433 and GRS 1915+105.
• Young Stellar Objects (YSOs)
  • Protostars or young stars in the process of forming.
  • Example: Herbig-Haro objects, which are visible manifestations of jets from YSOs interacting with the surrounding medium.
• Gamma-Ray Bursts (GRBs)
  • Highly energetic explosions thought to be associated with the collapse of massive stars or mergers of neutron stars.
  • Jets in GRBs are responsible for the intense gamma-ray emissions observed.

Significance in Astrophysics

• Jets provide insights into high-energy processes and the behavior of matter under extreme conditions.
• Study of jets helps understand the physics of accretion, magnetic fields, and relativistic flows.
• Jets can influence the evolution of galaxies by regulating star formation and heating the interstellar medium.
  • AGN jets, in particular, play a role in the feedback processes that affect galaxy formation and evolution.
• Observations of jets in distant quasars help probe the early universe and the growth of supermassive black holes.

BLACK HOLES, NEUTRON STARS, AND PULSARS Black Holes A black hole is a region in space where the gravitational pull is so strong that nothing, not even light, can escape from it.  It is formed from the remnants of a massive star that has ended its life cycle. Characteristics: Event Horizon: The boundary surrounding a black hole beyond which nothing can escape. The radius of the event horizon is known as the Schwarzschild radius. Singularity: The core of a black hole, where matter is thought to be infinitely dense and the laws of physics as we know them cease to apply. Accretion Disk: A disk of gas and dust that spirals into the black hole, heating up and emitting radiation due to the intense gravitational forces. Types: Stellar Black Holes: Formed from the collapse of a massive star, typically with masses ranging from about 3 to 20 times that of the sun. Supermassive Black Holes: Found at the centers of galaxies, including the Milky Way. They have masses ranging from millions to billions of solar masses. Intermediate Black Holes: With masses between stellar and supermassive black holes, their formation process is less understood. Primordial Black Holes: Hypothetical black holes formed during the early universe, with masses ranging from very small to large Neutron Stars A neutron star is the collapsed core of a massive star that underwent a supernova explosion. It is incredibly dense, composed almost entirely of neutrons. Characteristics: Density and Size: A typical neutron star has a mass about 1.4 times that of the sun but a radius of only about 10 kilometers, making it extremely dense. Magnetic Field: Neutron stars have extremely strong magnetic fields, up to a trillion times stronger than Earth's. Rotation: Neutron stars rotate very rapidly, sometimes hundreds of times per second. Types: Standard Neutron Stars: Exhibit the basic characteristics described above. Magnetars: Neutron stars with extraordinarily strong magnetic fields, which can cause high-energy electromagnetic radiation emissions. Pulsars: A type of neutron star that emits regular pulses of radiation, typically in the radio spectrum, due to its rapid rotation and strong magnetic field. Pulsars Pulsars are highly magnetized, rotating neutron stars that emit beams of electromagnetic radiation out of their magnetic poles. These beams sweep across the Earth at regular intervals, observed as pulses of radiation. Characteristics: Regular Pulses: Pulsars emit pulses with precise regularity, making them highly accurate cosmic clocks. Lighthouse Effect: The pulses are due to the lighthouse effect, where the radiation beams sweep across space as the neutron star rotates. Spin Rate: Can range from milliseconds to seconds. Millisecond pulsars are thought to have been spun up by accreting matter from a companion star. Types: Radio Pulsars: Emit mainly in the radio spectrum and are the most commonly observed type. X-Ray Pulsars: Emit X-rays, often due to accretion from a companion star. Gamma-Ray Pulsars: Emit gamma rays, detected by space-based telescopes.

Summary

Feature	Black Holes	Neutron Stars	Pulsars
Formation	Collapse of a massive star	Supernova explosion of a massive star	Rapidly rotating neutron stars
Mass	Varies: 3-20 solar masses (stellar), millions-billions (supermassive)	About 1.4 solar masses	Typically 1.4 solar masses
Size	Schwarzschild radius varies	Radius of about 10 km	Same as neutron stars
Density	Infinitely dense singularity	Extremely dense, primarily neutrons	Extremely dense, primarily neutrons
Magnetic Field	Extremely strong, especially in accretion disks	Extremely strong, up to a trillion times Earth's	Exceptionally strong, especially in magnetars
Rotation	N/A (event horizon has no physical surface)	Can rotate rapidly	Extremely rapid, from milliseconds to seconds
Radiation Emission	X-rays, gamma rays, radio waves (from accretion disk and jets)	X-rays, gamma rays (hot surface or accretion)	Radio waves, X-rays, gamma rays (pulsed emission)
Observation	X-ray telescopes, gravitational wave detectors, EHT	X-ray, gamma-ray, and radio telescopes	Radio telescopes, X-ray and gamma-ray telescopes

Plasma

• Plasma is often referred to as the fourth state of matter, distinct from solids, liquids, and gases.
• It consists of a collection of free-moving electrons and ions (atoms that have lost electrons). Plasmas are found naturally in stars, including the sun, and are also created in various industrial and scientific applications.

Characteristics of Plasma

• Ionization
  • Plasma is formed when a gas is ionized, meaning some of the electrons are stripped away from their atoms.
  • This ionization can be achieved through heating or by applying a strong electromagnetic field.
• Conductivity: Plasmas are highly conductive because they contain free electrons and ions that can move independently.
• Collective Behavior: Particles in a plasma interact with each other through electromagnetic forces, leading to collective behavior that is different from that of gases.
• Temperature: Plasma temperatures can range from relatively low (in the case of plasmas in fluorescent lights) to extremely high (such as in stars).
• Electric and Magnetic Fields: Plasmas are affected by electric and magnetic fields, which can influence their behavior and structure.

Types of Plasma

• Thermal Plasma: Both electrons and ions are at thermal equilibrium, meaning they have roughly the same temperature. Examples: Stars, lightning, and arc welding.
• Non-Thermal Plasma: Electrons are at a much higher temperature than the ions and neutral particles. Examples: Fluorescent lights, plasma TVs, and cold plasma used in medical treatments.

Applications of Plasma

• Industrial Applications
  • Plasma Cutting:Uses a jet of hot plasma to cut through metals.
  • Plasma Etching:Used in semiconductor manufacturing to etch fine patterns.
  • Surface Modification:Plasmas can alter the surface properties of materials, such as making them more hydrophilic or hydrophobic.
• Medical Applications
  • Plasma Medicine:Uses non-thermal plasmas for sterilization, wound healing, and cancer treatment.
  • Plasma Coating:Applies biocompatible coatings to medical implants.
• Environmental Applications
  • Waste Treatment:Plasma technology can break down hazardous waste into less harmful substances.
  • Water Purification:Plasma can be used to remove contaminants from water.

Plasma in Nature

• Astrophysical Plasmas
  • Stars:The core of stars is a hot plasma where nuclear fusion occurs.
  • Solar Wind:A stream of plasma released from the upper atmosphere of the sun.
  • Nebulae:Clouds of ionized gas in space.
• Terrestrial Plasmas
  • Lightning:A natural plasma created by the discharge of electricity during a thunderstorm.
  • Auroras:Natural light displays in the Earth's polar regions caused by the interaction of the solar wind with the Earth's magnetosphere.

Summary of the forms of matter

State of Matter	Structure and Particles	Properties	Examples
Solid	Particles are closely packed in a fixed, orderly arrangement.	Definite shape and volume; particles vibrate but do not move freely.	Ice, iron, diamond
Liquid	Particles are closely packed but not in a fixed arrangement, allowing them to flow past one another.	Definite volume but no definite shape; takes the shape of the container; particles move more freely.	Water, oil, alcohol
Gas	Particles are widely spaced and move independently of one another.	No definite shape or volume; expands to fill the container; particles move rapidly and randomly.	Air, helium, carbon dioxide
Plasma	Consists of free electrons and ions (charged particles); ionized gas.	Highly conductive; affected by magnetic and electric fields; emits light when electrons recombine with ions.	Stars, lightning, neon signs
Bose-Einstein Condensate (BEC)	Atoms cooled to near absolute zero, causing them to occupy the same space and quantum state, behaving as a single quantum entity.	Very low temperature; particles are in the lowest quantum state; exhibits superfluidity and coherence.	Supercooled rubidium atoms, helium-4 at very low temperatures
Fermionic Condensate	Similar to BEC but formed with fermions; pairs of fermions act like bosons at very low temperatures.	Very low temperature; fermion pairs exhibit superfluidity; complex quantum behavior.	Lithium-6 atoms at ultra-low temperatures
Quark-Gluon Plasma	Consists of quarks and gluons, fundamental particles that make up protons and neutrons; occurs at extremely high temperatures and densities.	Exists at extremely high energy levels; quarks and gluons are free from their usual confinement within protons and neutrons.	Conditions shortly after the Big Bang, created in particle accelerators like the Large Hadron Collider

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PIB

PRACTICE QUESTION Q: Consider the following statements regarding Astro Jets: Astro jets are high-speed jets of gas and dust ejected from the polar regions of young stars and active galactic nuclei. Astro jets are powered by magnetic fields generated by the rotating accretion disk surrounding the star or black hole. The presence of astro jets is often an indicator of ongoing star formation or active galactic nuclei in a galaxy. Which of the statements given above is/are correct? a) 1 and 2 only b) 2 and 3 only c) 1 and 3 only d) 1, 2, and 3 Answer: d)