Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1 Announcements: -Extra Credit opportunity this Friday Evergreen Valley College 7PM-10:30 check website for weather information maps available online Pick up copy of handout: required for credit!!
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 2 The H-R diagram Figure 12.16
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 3 Stellar luminosity classes ISupergiants IIBright Giants (not widely used) IIIGiants IVSubgiants VDwarfs (Main Sequence Stars) White Dwarfs
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 4 H-R diagram showing where stars of a given radius will lie Figure 12.18
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 5 L~M 3 Mass and Luminosity of Main Sequence Stars
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 6 Chapter 13
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 7 Introduction Where do stars come from? How do they age (evolve) What is their fate?
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 8 Where do Stars Come From?
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 9 infra-red detectors allow us to see inside of giant molecular clouds where stars are currently forming. we see groups of relatively young stars the galaxy is still full of the raw materials from which stars form (Interstellar clouds) How do we know new stars are forming in our galaxy right now?
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 10 Interstellar Gas Clouds: General Characteristics Gas: hydrogen (71%), Helium (27%), othersGas: hydrogen (71%), Helium (27%), others Hydrogen is in molecular form (H 2 )Hydrogen is in molecular form (H 2 ) Dust: microscopic particles of silicates, carbon, and ironDust: microscopic particles of silicates, carbon, and iron Temperature: Around 10 KTemperature: Around 10 K Densities: grams/ccDensities: grams/cc
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 11 The Eagle Nebula Hubble Space Telescope image Giant Molecular Clouds
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 12 Dense Globules Unveiled Revealing a Stellar Nursery
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 13 How do stars form?
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 15 1.Giant Molecular Cloud breaks up into smaller clumps that collapse under their own gravity. 2.Rotation becomes more and more important as clump contracts. 3.Disk forms 4.Bi-polar jets are created; Cloud clears away
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 16 Protostar: When cloud becomes dense enough and hot enough that it radiates as a blackbody.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17 Characteristics of Protostars Temperature: About 1500 K Shine at infrared and radio wavelengths Low temperature and obscuring dust prevents visible detection May be found in “Bok globules”, dark blobs LY across with masses of up to 200 solar masses
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 18 Photo of an interstellar cloud Figure 7.7 Bok Globule
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 20 Vocabulary List Interstellar Medium Giant Molecular Cloud Bok Globule Protostar