2004 ASTRONOMY & ASTROPHYSICS - Indian Academy of Sciences

CHAPTER 7
Theoretical Astrophysics
Theoretical astrophysics has a long tradition in
India, and has been actively pursued both at
university departments and, in more recent times,
at various research institutions. Since theoretical
astrophysics encompasses a very wide spectrum
of topics, it would not be possible to give a
detailed overview of the development of the
subject during the past 90 years or so. The
fundamental work of Saha and Chandrasekhar laid
the foundation on which much of the
superstructure of stellar astrophysics was built.
During the subsequent decades, theoretical
research in astrophysics included a wide range of
topics:
• Stars
• Internal structure and stability
• Stellar atmospheres and radiative transfer
• Stellar evolution
• The Sun and solar system objects
• Interstellar Medium
• HII regions
• Planetary nebulae
• Diffuse interstellar clouds
• Giant molecular clouds
• Supernova remnants, and their interaction
with the ISM
• Neutron Stars
• The origin and evolution of neutron stars
• The equation of state of neutron stars
• The magnetic fields of neutron stars and their
evolution
• The birth rate of pulsars
• Radio emission from pulsars
• Binary and millisecond pulsars
• Dynamics of stellar systems
• The composition, structure and
dynamics of galaxies
• Radio galaxies and quasars
• Gravitational lenses
• General relativity and gravitation
• Large-scale structures in the Universe
• Cosmology
Over the years there have been a number of quite
significant contributions in many of these topics.
Indeed, some of them have been acclaimed
internationally. A partial list of some of the
important results is given below.
• Pioneering studies of the roles played by
molecular energy bands in essential physical
processes in stellar atmospheres and giant
molecular clouds resolved long-standing
problems.
• A new class of recycled pulsars from accretiondriven
spin-up of neutron stars in binary
systems was proposed, and binary and
millisecond pulsars were identified as such
recycled pulsars.
• From statistical studies of the population of
pulsars and associated nebulae, evidence was
found of pulsars being born spinning slowly.
• Magnetic fields of neutron stars were shown to
decay mainly due to their interaction with
binary companions. A novel mechanism for this,
involving the superconducting - superfluid
interior, and ohmic processes in the crust, was
identified.
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