ASTRONOMICAL TRANSIENTS

Source: HINDU

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Context

• Shrinivas Kulkarni, a prominent Indian-American astronomer, was recently honored with the 2024 Shaw Prize for Astronomy for his pioneering work on the physics of these transients.

Details

• Astronomical transients are objects or events in the sky that change in brightness, position, or both, over relatively short timescales, ranging from milliseconds to years.

SHAW PRIZE The Shaw Prize refers to three annual awards presented by the Shaw Prize Foundation in the fields of astronomy, medicine and life sciences, and mathematical sciences. Established in 2002 in Hong Kong by Hong Kong entertainment mogul and philanthropist Run Run Shaw, the awards honour "individuals who are currently active in their respective fields and who have recently achieved distinguished and significant advances, who have made outstanding contributions in academic and scientific research or applications, or who in other domains have achieved excellence." The prize has been described as the "Nobel of the East.

Astronomical Transients

• Astronomical transients are classified based on their duration, luminosity, and underlying physical mechanisms.
• They provide valuable information about extreme astrophysical processes and are often associated with high-energy phenomena such as supernovae, gamma-ray bursts, and neutron star mergers.

Supernovae

Supernovae are explosive events marking the end of a star's life cycle, resulting in a significant increase in brightness.

• Type Ia Supernovae:
  • Caused by the thermonuclear explosion of a white dwarf in a binary system.
  • Serve as standard candles for measuring cosmic distances.
• Core-Collapse Supernovae:
  • Occur when massive stars exhaust their nuclear fuel and their cores collapse under gravity.
  • Subtypes include Type II, Type Ib, and Type Ic.

Gamma-Ray Bursts (GRBs)

GRBs are intense bursts of gamma radiation originating from distant galaxies.

• Long GRBs:
  • Lasting more than 2 seconds.
  • Associated with the collapse of massive stars (hypernovae).
• Short GRBs:
  • Lasting less than 2 seconds.
  • Linked to the mergers of compact objects such as neutron stars.

Fast Radio Bursts (FRBs)

FRBs are brief, intense bursts of radio waves, lasting milliseconds.

• Origin: Still largely unknown, but potential sources include magnetars and neutron star mergers.
• Significance: Probes of the intergalactic medium and dark matter.

Tidal Disruption Events (TDEs)

TDEs occur when a star gets too close to a supermassive black hole and is torn apart by tidal forces.

• Observations: Emission in ultraviolet, X-rays, and sometimes radio waves.
• Importance: Provides insights into black hole properties and accretion processes.

Novae

Novae are eruptions on the surface of a white dwarf in a binary system, caused by accretion of hydrogen from a companion star.

• Classical Novae: Single explosive event.
• Recurrent Novae: Multiple eruptions over time.

Observation Techniques and Instruments

Optical Telescopes

• Ground-based: E.g., Keck Observatory, Very Large Telescope (VLT).
• Space-based: E.g., Hubble Space Telescope (HST).

Radio Telescopes

• Examples: Arecibo Observatory, Very Large Array (VLA), Square Kilometre Array (SKA).

X-ray and Gamma-ray Observatories

• Examples: Chandra X-ray Observatory, XMM-Newton, Fermi Gamma-ray Space Telescope.

Gravitational Wave Detectors

• Examples: LIGO, Virgo, KAGRA.

Scientific Implications

Cosmology

• Standard Candles: Type Ia supernovae for measuring cosmic distances and the expansion rate of the universe.
• Dark Energy and Dark Matter: Constraints from transient observations.

Stellar Evolution

• Life Cycles of Stars: Insights into the final stages of stellar evolution from supernovae and novae.
• Stellar Remnants: Formation of neutron stars, black holes, and white dwarfs.

High-Energy Astrophysics

• Extreme Physics: Understanding high-energy processes and particle acceleration mechanisms.
• Magnetic Fields: Study of magnetars and the role of magnetic fields in transients.

Sources:

HINDU

PRACTICE QUESTION Q.  Astronomical transients are key to understanding a wide range of astrophysical phenomena. Comment. (250 Words)