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Pitt ASTRON 0089 - Types of Nebulae, 21 cm Radiation, Star Evolution, Star Clusters

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a. Interstellar gas emits low-energy radiation, due to a transition in the H atomi. The spin has a direction, proton and electron have same spin pointing in same direction which is higher in E than if they two had opposite spinsii. When they are opposite, they emit a photon at a wavelength of 21 cm.b. Another way of probing the interstellar media (using radio telescopes)c. The densest clouds are also very cold, around 20 Ka. Stage 1: interstellar stars starts to contract; shock causes fragmentationb. Stage 2: individual cloud fragments begin to collapse; once the DENSITY is high enough, there is no further fragmentation (no more splitting up into pieces)c. Stage 3: interior of each fragment gets higher in density, and therefore hotter in temperature (more and more particles are jostling for space)i. Core is about 10,000 Kii. Surface Temp about 300 Kd. Stage 4: protostar forms. NOT a star yet. Protostar = T Tauri star (synonymous)i. Core is about 150,000, when core begins to have nuclear fusion reactions that is when it will be considered a star (when it can generate its own energy)ii. Surface Temp about 4500 Kiii. Protostar makes its first appearance on the H-R diagram; this means it has an L and a T that are within the range of this plotiv. It is getting its own energy from GRAVITY1. Gravitational potential energy becomes converted to heat and lighte. Stage 5: Planetary formation has begun, but the protostar is till not in equilibrium – all heating comes from the gravitational collapsef. Stage 6: the core reaches 10 million K, and nuclear fusion begins. The protostar has become a star.i. Star has now reached the main sequence and will remain there as long as it fuses Hydrogeng. Stage 7: the star is in equilibriumi. Core Temp: 15 milliona. Generates its own energy in its core! (Thermonuclear reactions)b. Has to be massive enoughi. Must have .08 Mass of the Sun (80 times the mass of Jupiter) in order to become DENSE AND HOT enough that fusion can begin1. If mass is not up to par, it is considered a “failed star” = brown dwarfa. Clusters of stars are useful because they share: age, composition, and same distance from usASTRON 89 1nd Edition Lecture 22Outline of Last Lecture I. Stellar MassesII. Correlations and Relationships Important to Stellar MassesIII. The Interstellar Medium Outline of Current Lecture I. The Interstellar Medium: Consists Gas and DustII. Types of NebulaeIII. 21 cm radiationIV. Star EvolutionV. Requirements for a stellar object to be called a star:VI. Star clusters all form at approximately the same time, because when one star forms it triggers the formation of others. VII. Tripe alpha processCurrent LectureI. The Interstellar Medium: Consists Gas and Dusta. Stars form from the contents in the interstellar mediumb. It contains a lot of dust i. Dust adds up and can add up and hide star; it clumps together, reddening the lightc. Dust affects light in two ways: i. Scatters light; light is diminished so it becomes DIMMER1. Extinction phenomenon ii. Light is REDDENED 1. Reddening phenomenon II. Types of Nebulaea. Emission nebulae:i. HII Regions ii. The Rosette Nebula iii. Light is being emitted by the gas (ionized gas)iv. Red due to Hydrogen emission v. Made of hot, thin gas, which exhibits distinct emission lines These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. Reflection nebulae:i. The Pleiades ii. Blue is reflection of starlight off dust iii. Dust scatters light away from the source; smearing light (reflecting starlightc. Dark nebula: i. Horsehead nebula 1. One of the most famous dark dust clouds ii. Very dense III. 21 cm radiationa. Interstellar gas emits low-energy radiation, due to a transition in the H atom i. The spin has a direction, proton and electron have same spin pointing in same direction which is higher in E than if they two had opposite spins ii. When they are opposite, they emit a photon at a wavelength of 21 cm.b. Another way of probing the interstellar media (using radio telescopes)c. The densest clouds are also very cold, around 20 K d. These clouds tend to contain molecules rather than atoms IV. Star Evolution a. Stage 1: interstellar stars starts to contract; shock causes fragmentation b. Stage 2: individual cloud fragments begin to collapse; once the DENSITY is high enough, there is no further fragmentation (no more splitting up into pieces)c. Stage 3: interior of each fragment gets higher in density, and therefore hotter in temperature (more and more particles are jostling for space) i. Core is about 10,000 Kii. Surface Temp about 300 Kd. Stage 4: protostar forms. NOT a star yet. Protostar = T Tauri star (synonymous)i. Core is about 150,000, when core begins to have nuclear fusion reactions that is when it will be considered a star (when it can generate its own energy) ii. Surface Temp about 4500 K iii. Protostar makes its first appearance on the H-R diagram; this means it hasan L and a T that are within the range of this plot iv. It is getting its own energy from GRAVITY 1. Gravitational potential energy becomes converted to heat and light e. Stage 5: Planetary formation has begun, but the protostar is till not in equilibrium– all heating comes from the gravitational collapse f. Stage 6: the core reaches 10 million K, and nuclear fusion begins. The protostar has become a star. i. Star has now reached the main sequence and will remain there as long as it fuses Hydrogen g. Stage 7: the star is in equilibriumi. Core Temp: 15 million h. T surface: 5,8000 Ki. Once the star reaches the main sequence, it DOES NOT MOVE, it stays there until it runs out of fuel i. The pre – main sequence evolution is called the Hayashi Track V. Requirements for a stellar object to be called a star:a. Generates its own energy in its core! (Thermonuclear reactions)b. Has to be massive enoughi. Must have .08 Mass of the Sun (80 times the mass of Jupiter) in order to become DENSE AND HOT enough that fusion can begin1. If mass is not up to par, it is considered a “failed star” = brown dwarfVI. Star clusters all form at approximately the same time, because when one star forms it triggers the formation of others.a. Clusters of stars are useful because they share: age, composition, and same distance from usb. Which is important for inverse square law, which tells us their relative LUMINOSITIES, because if they’re all the same distance, then


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Pitt ASTRON 0089 - Types of Nebulae, 21 cm Radiation, Star Evolution, Star Clusters

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