PHYS 190 Lecture Notes - Lecture 10: Main Sequence, Faraday Cage, Star Formation
27 Nov 2020
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Recall: colour index & temperature: simplest estimates use two filters: blue and green (visual, mb-mv < 0 : bluer, mb-mv > 0 : redder, mb-mv approx. Interstellar medium (ism): incubator of new stars: 99% gas and 1% dust* by mass, *not unlike smoke grains. Ism chemical composition similar to the sun: 75% hydrogen, 25% helium (approx, by mass, trace of heavier elements. Ism is generally closer to a vacuum than in any lab: dust blocks visible light from beyond a few thousand light years. Ism and interstellar reddening: long wavelength red, infrared and radio light can partially get around dust particles, while blue light gets scattered. Star formation: cold dense pockets of ism, but warm enough to support own weight, gravitational collapse can be triggered by a shock wave" generated by nearby exploding star, or a passing star. 1 light-year wide fragments of larger clouds: as fragments collapse, centres warms to thousands of degree: protostar.
