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Radio Waves Interaction With Interstellar Matter

Dive into the interaction of radio waves with interstellar matter, exploring the cosmic realm brought to you by McGourty-Rideout. Understand the interstellar medium, from gaseous hydrogen to ionized hydrogen near hot stars, and the significance of the 21-cm line radiation. Discover how the energy state of electrons influences hydrogen atoms emitting radio energy and the uses of the 21cm line in mapping the galaxy's structure. Witness how waves are transformed in space, affected by interstellar gas, plasma, molecules, and gravitational fields, showcasing the wonders of the universe.

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Radio Waves Interaction With Interstellar Matter

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  1. Radio Waves Interaction With Interstellar Matter A cosmic journey brought to you by McGourty-Rideout

  2. Interstellar Medium • Gaseous - almost all hydrogen • H I- neutral hydrogen one proton and one electron( most) • H II ionized hydrogen- - no electron just a proton - near hot stars • Dust – C, N, and silicates

  3. 21-cm line Radiation • Radio emission from hydrogen when an electron “flips its spin” • H I gas emits a particular wavelength of radio energy from an energy change in the hydrogen atoms. The wavelength is 21.1cm (frequency = 1420.4 MHz) • called 21-cm line radiation • Temperatures between 100 K to about 3000 K

  4. 21-cm line Radiation • An electron moving about a proton can have a spin in the same direction as the proton or in the opposite direction • The energy state of an electron spinning opposite is slightly lower than the energy state when both are in the same direction

  5. 21-cm line Radiation • Atoms always want to be in the lowest energy state • If the spins are in the same direction, the electron will eventually flip to the opposite spin direction • The energy difference is very small, so a hydrogen atom may wait a few million years before it undergoes this transition

  6. Uses of 21cm Line • The Milky Way alone has about 3 billion solar masses of H I gas so enough hydrogen atoms are emitting the 21-cm line radiation to be easily detected with radio telescopes • Not blocked by dust • Best way to map the structure of the galaxy • Radio emission leads to penetration

  7. Waves Transformed in Space • Slowed down & refracted by interstellar gas and plasma • Spectral lines absorbed by interstellar molecules & atoms • Doppler shifted by moving sources

  8. Waves Transformed in Space • Slowed down & refracted by strong gravitational fields • Red shifted by gravitational sources • Polarization rotated by magnetic fields

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