ASTROPHYSICAL JETS - SCIENCE

ASTROPHYSICAL JETS - SCIENCE

News: 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.

 

What’s in the news?

  • 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

o    Jets are often formed in the regions surrounding accretion disks around black holes, neutron stars, or young stars.

o    Magnetic fields in the accretion disk play a crucial role in launching and collimating the jets.

  • Magnetohydrodynamic (MHD) Processes

o    Interaction between the magnetic fields and ionized plasma in the disk.

o    The twisting of magnetic field lines can create a magnetic spring that accelerates particles along the field lines, forming jets.

  • Radiation Pressure

o    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

o    Associated with supermassive black holes at the centers of galaxies.

o    Can extend for thousands to millions of light-years.

o    Example: The jet from the galaxy M87, famously imaged by the Event Horizon Telescope.

  • Microquasars

o    Stellar-mass black holes or neutron stars with jets.

o    Example: SS 433 and GRS 1915+105.

  • Young Stellar Objects (YSOs)

o    Protostars or young stars in the process of forming.

o    Example: Herbig-Haro objects, which are visible manifestations of jets from YSOs interacting with the surrounding medium.

  • Gamma-Ray Bursts (GRBs)

o    Highly energetic explosions thought to be associated with the collapse of massive stars or mergers of neutron stars.

o    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.

o    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.

 Source: https://pib.gov.in/PressReleseDetailm.aspx?PRID=2031586