The Interstellar Medium (Lecture - 03) by Professor G Srinivasan

Summer course 2018 - A Random walk in astro-physics

Lecture - 03 : The Interstellar Medium
by Professor G Srinivasan, Raman Research Institute (Retired)

10.00 to 12.00 Wednesday, 16 May 2018
Madhava Lecture Hall, ICTS Bangalore

The range of densities, temperatures, magnetic fields, etc. that obtain in the Universe are staggering: from 10-27 g cm-3 to 1015 g cm-3, from 3K to 1010 K, from 10-6 G to 1015 G. Not surprisingly, the variety of physical phenomena one encounters during the study of celestial objects is truly impressive. This set of lectures is intended to illustrate the richness of Astrophysics. It will be a random walk in basic physics, with numerous illustrations from astronomy. The topics in physics that will be reviewed have been chosen on the basis of their importance in contemporary astronomy.

Topics:

Absorption and emission of radiation
Radiation from relativistic electrons
Compton scattering of radiation
Spontaneous and stimulated emission
Hyperfine splitting of energy levels
Molecular spectra
Astrophysical plasma.
Quantum tunnelling.
Nuclear matter
Neutrino Oscillation
Phase transitions and the early Universe
During this random walk in physics, one will encounter a range of astronomical objects and phenomena, such as, Solar wind, gaseous nebulae, interstellar hydrogen clouds, giant molecular clouds, neutron stars and pulsars, supernova remnants, radio galaxies and quasars, active galactic nuclei, the cosmic microwave background, etc.

https://www.icts.res.in/summercourse2018

Table of Contents (powered by https://videoken.com)
0:00:00 Summer course 2018 - A Random walk in astro-physics
0:00:10 The Interstellar Medium (Lecture-03)
0:01:15 The Interstellar Medium
0:03:43 Star cluster NGC 265
0:08:03 As we journey through the interstellar space, we will encounter spectacular gaseous nebula and remnants of supernovae.
0:08:24 The great nebula in Orion
0:08:31 The horse head nebula
0:08:38 Pillars of dust in the Eagle Nebula
0:09:02 Cassiopeia A, the expanding supernova remnant
0:09:33 X-ray image of the remnant of TYCHO's supernova of 1572
0:10:03 Discovery of 21 cm radiation from Hydrogen
0:23:12 Discovery of interstellar hydrogen was one of the greatest discoveries in the history of astronomy. It revolutionized astronomy
0:27:05 The "Doppler shifted frequencies" will be different for the three clouds
0:30:25 Modelling the distribution of neutral hydrogen in the Galaxy
0:31:54 Random motion of clouds superimposed on their systematic motion around the center of the Galaxy.
0:32:09 The distribution of the neutral hydrogen gas in the Milky Way.
0:45:53 Raisin pudding model of the Interstellar Medium
0:55:21 Interstellar Medium Molecular Gas
0:55:31 Molecular Spectra
0:57:40 Rotational spectrum: A rotating molecule will radiate only if it has a permanent electric dipole moment.
1:01:15 Spectral region of rotational transitions
1:04:46 Vibrational levels
1:08:51 Molecules in interstellar space
1:16:35 Giant Molecular Clouds
1:19:26 All or nothing
1:22:36 M 51 - Whirlpool Galaxy. Right is the visible image. The dark lanes trace the distribution of dust.
1:23:25 Distribution of molecular clouds is shown in blue
1:25:30 A star cluster in the Rosette Nebula. The wavelength of the recombination radiation will tell us about the composition of the gas.
1:26:15 Some 'compression wave' triggers a burst of star formation. A young star cluster is born.
1:29:57 Celestial Masers
1:30:18 The OH maser was the first celestial maser to be discovered in 1965.
1:32:57 Maser environment
1:33:40 Comet Schumaker-Levy hitting Jupiter (1994)
1:34:21 Extragalactic MEGA MASERS
1:38:03 Next Lecture: Radiation from Accelerated Charges
1:39:05 Q&A

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