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The Interstellar Medium

The Interstellar Medium. ISM Properties - 99% is gas, mostly H, He - about 1 atom/cm 3 - 1% is dust grains, mostly C, ices of water, ammonia, methane - 10 -6 meters in diameter - about 1 grain/100m 3. ISM Properties (continued) - Temps between 5K to 10,000K near hot stars

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The Interstellar Medium

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  1. The Interstellar Medium

  2. ISM Properties - 99% is gas, mostly H, He - about 1 atom/cm3 - 1% is dust grains, mostly C, ices of water, ammonia, methane - 10-6 meters in diameter - about 1 grain/100m3

  3. ISM Properties (continued) - Temps between 5K to 10,000K near hot stars - About 10% of the mass of our Galaxy is ISM

  4. HII regions - ionized regions around hot stars Ionized H (HII) Hot O,B star

  5. 30 Doradus (Trantula Nebula)

  6. The ISM absorbs short wavelengths more than long ones -> the ISM reddens and dims starlight

  7. 21-cm Radiation H-Atom Low energy High Energy 21 cm photon

  8. Nebulae (clouds) - Concentrations in the ISM (1,000’s of atoms/cm3) - The building blocks of the Stars

  9. Dark Nebulae - lots of Dust Horsehead Nebula

  10. Keyhole Nebula

  11. Reflection Nebulae - shine by reflected light from nearby stars Witch Head Nebula

  12. Orion Nebula

  13. Trifid Nebula

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