PHY121 Ch 9-11 Vocab

PHY121 Ch 9-11 Vocab - Chapter 9: Interstellar medium the...

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Chapter 9: Interstellar medium – the gas and dust distributed between the stars Nebula – a glowing cloud of gas or a cloud of dust reflecting the light of nearby stars Emission nebulae – a cloud of glowing gas excited by ultraviolet radiation from hot stars HII regions – a region of ionized hydrogen around a hot star Reflection nebulae – a nebula produced by starlight reflecting off dust particles in the interstellar medium Interstellar dust – microscopic solid grains in the interstellar medium Interstellar reddening – the process in which dust scatters blue light out of starlight and makes the star look redder Molecular clouds – a dense interstellar gas cloud in which atoms are able to link together to form molecules such as H 2 and CO Shock wave – a sudden change in pressure that travels as an intense sound wave Protostar – a collapsing cloud of gas and dust destined to become a star Star cluster – a group of stars that formed together and orbit a common center of mass Association – group of widely scattered stars (10 to 100) moving together through space. Not gravitationally bound into clusters Evolutionary track – the path a star follows in the H-R diagram as it gradually changes its surface temperature and luminosity Birth line – in the H-R diagram, the line above the main sequence where protostars first become visible T Tauri stars – a young star surrounded by gas and dust, believed to be contracting toward the main sequence Bok globules – small, dark cloud only about 1ly in diameter that contains 10 to 1000 solar masses of gas and dust, believed to be related to star formation Bipolar flows – jets of gas flowing away from a central object in opposite directions. A term usually applied to protostars Herbig-Haro objects – a small nebula that varies irregularity in brightness, believed to be associated with star formation Star formation pillars – the column of gas produced when a dense core of gas protects the
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PHY121 Ch 9-11 Vocab - Chapter 9: Interstellar medium the...

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