Explore the fascinating world of the interstellar medium in this comprehensive 2-hour lecture by Professor G Srinivasan from the Raman Research Institute. Delve into the staggering range of densities, temperatures, and magnetic fields found in the universe, from 10-27 g cm-3 to 1015 g cm-3 and 3K to 1010 K. Discover the richness of astrophysics through topics such as absorption and emission of radiation, Compton scattering, spontaneous and stimulated emission, molecular spectra, and astrophysical plasma. Encounter a variety of astronomical objects including solar wind, gaseous nebulae, interstellar hydrogen clouds, neutron stars, pulsars, and active galactic nuclei. Learn about the groundbreaking discovery of 21 cm radiation from hydrogen and its impact on astronomy. Explore the distribution of neutral hydrogen in the Galaxy, molecular gas in the interstellar medium, and the formation of giant molecular clouds. Gain insights into celestial masers, including the first OH maser discovery in 1965 and extragalactic mega masers. Conclude with a Q&A session and a preview of the next lecture on radiation from accelerated charges.
The Interstellar Medium by Professor G Srinivasan
International Centre for Theoretical Sciences via YouTube
Overview
Syllabus
Summer course 2018 - A Random walk in astro-physics
The Interstellar Medium Lecture-03
The Interstellar Medium
Star cluster NGC 265
As we journey through the interstellar space, we will encounter spectacular gaseous nebula and remnants of supernovae.
The great nebula in Orion
The horse head nebula
Pillars of dust in the Eagle Nebula
Cassiopeia A, the expanding supernova remnant
X-ray image of the remnant of TYCHO's supernova of 1572
Discovery of 21 cm radiation from Hydrogen
Discovery of interstellar hydrogen was one of the greatest discoveries in the history of astronomy. It revolutionized astronomy
The "Doppler shifted frequencies" will be different for the three clouds
Modelling the distribution of neutral hydrogen in the Galaxy
Random motion of clouds superimposed on their systematic motion around the center of the Galaxy.
The distribution of the neutral hydrogen gas in the Milky Way.
Raisin pudding model of the Interstellar Medium
Interstellar Medium Molecular Gas
Molecular Spectra
Rotational spectrum: A rotating molecule will radiate only if it has a permanent electric dipole moment.
Spectral region of rotational transitions
Vibrational levels
Molecules in interstellar space
Giant Molecular Clouds
All or nothing
M 51 - Whirlpool Galaxy. Right is the visible image. The dark lanes trace the distribution of dust.
Distribution of molecular clouds is shown in blue
A star cluster in the Rosette Nebula. The wavelength of the recombination radiation will tell us about the composition of the gas.
Some 'compression wave' triggers a burst of star formation. A young star cluster is born.
Celestial Masers
The OH maser was the first celestial maser to be discovered in 1965.
Maser environment
Comet Schumaker-Levy hitting Jupiter 1994
Extragalactic MEGA MASERS
Next Lecture: Radiation from Accelerated Charges
Q&A
Taught by
International Centre for Theoretical Sciences
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