ASTRON 1F03 Lecture Notes - Lecture 25: Local Bubble, Molecular Cloud, Radiography
18 Dec 2015
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Document Summary
The sun resides in a local bubble of million-degree gas. Hydrogen heated and ionized by uv light from hot, luminous stars (o and b). At lower temperatures, hydrogen is in single, neutral atoms. Good for mapping the milky way primary way to get detailed rotation curves. This gas emits radio waves with = 21 cm. Some clouds can have masses as large as 10 million times that of the sun. Much of the gas is in cool interstellar clouds, with hotter intercloud gas between them. Molecular clouds: cold enough for hydrogen to exist as the h2 molecule. Cosmic rays form in supernova shocks relativistic particles near speed of light. Molecular clouds anchor milky way"s magnetic field. Cosmic rays high-energy, charged particles can be trapped. Ages of clusters come from main-sequence turnoff. Globular clusters (and other old star in the halo) can be > 10 billion years old. Open clusters (in the disk) are much younger!
