REVIEW GUIDE FOR EXAM 2 ON MAY 4 2005 (ASTRO 301/ 46690) OVERVIEW --------- The exam on May 4, 2005 will be based mainly on in-class notes. It will cover some of the topics listed below. There may also be a few questions on topics which are not explicitly listed below, but which were discussed in class. Note that this exam will NOT follow the homeworks as closely as the first exam did. The questions will test *principles* similar to those addressed by the homework, but the questions may differ significantly. The extra credit earned by those who participated in class will be added to the exam grade or to the overall final grade for the semester. REVIEW TOPICS ------------- ===== Review questions on homeworks 4 to 8 and quizzes 2 to 6. ===== Properties, Formation, and Evolution of Stars -- Basic Properties of stars - The relation between flux, luminosity, and distance of a star - How does the Sun generate its luminosity ? - When 1 kg of hydrogen is fused to helium, does it generate more or less energy than when 1 kg of helium is fused to carbon? Why? - Why is there no energy generated if iron is fused? -- The H-R diagram - The relationship between luminosity, radius and temperature (L, R, T) for stars on the HR diagram. - The reason for the wide range in (L R T) on the H-R diagram. -- Thermal pressure, radiation pressure, and degeneracy pressure. The type of objects where each form of pressure is important. NOTE: Above issues were discussed in class on Fri Apr 8. -- How stars of low (M<=1 Msun), intermediate (M=2-8 Msun) , and high (M>8 Msun) mass differ in terms of the following properties: a) The type of fusion and the dominant form of pressure support in the stellar core when the star is still on the main sequence. b) The main sequence lifetime of the star. c) The evolution of the star as it leaves the main sequence. (The red giant, red supergiant, and blue supergiant phases) d) The most advanced stages of fusion that occur in the core. e) The nature and chemical composition of the end-products generated when the star dies. NOTE: The above issues were summarized in a short table (1.5 page) in class on Wed Apr 13. See also the 1-page powerpoint figures on Apr 4 and Apr 6 summarizing the evolution of a low and high mass star on the HR diagram. THIS TABLE AND THESE TWO FIGURES OUTLINE THE KEY IDEAS FROM 3 CHAPTERS OF THE BOOK. I STRONGLY RECOMMEND THAT YOU GET THEM. -- Why are we made of 'star stuff'? Why do need both high and low mass stars for life on Earth to exist? -- How do we use H-R diagrams to get the age of stellar clusters? How does the age estimate depends on metallicity assumed? What is the estimated age for the oldest cluster? NOTE: Above issues were discussed in class on Fri Apr 15. ===== Properties, Formation and Evolution of Galaxies -- Galaxy classification - Types of Galaxies according to their structure and morphology: spirals,ellipticals, irregulars, dwarfs, peculiar/interacting. - The Hubble Sequence and its limitation as a classification scheme. -- Mapping the distance to stars and galaxies - Distance ladder: Stellar parallax, Main sequence fits, Cepheid period-luminosity relation, Peak luminosity of white dwarf supernovae, Tully Fisher relation for spirals. - Using Hubble's law and Doppler redshift to get galaxy distances. -- Mapping stars (old and young) and gas (cold and hot) in galaxies via multi-wavelength observations: X-ray, UV, optical, IR, radio. -- Mapping dark matter in the Universe - How to map dark matter in spirals, elliptical, and galaxy clusters. - Candidates for baryonic dark matter (MACHOS), non-baryonic cold dark matter (e.g., WIMPS), hot dark matter (neutrinos) and current or future observations to detect them.. -- Galaxy Interactions - Major mergers and the Toomre sequence. Minor and intermediate mergers - Interactions of the Milky Way. - Interactions at early times, 12 billion years ago. -- How do we study the formation and evolution of galaxies? - The critical need for high resolution images and redshifts (distances). - What epochs and areas do different galaxy surveys, such as the Hubble Ultra Deep Field and GEMS cover? What have these surveys taught us? ===== The Universe: Its Beginning and its Possible Fates YOU WILL ONLY NEED TO KNOW THE (**) ITEMS -- Unifying Fundamental Forces as Electroweak, GUT, and Super forces -- The Beginning of Time: From 10-43 s to to the First Second - The Planck era , GUT era , and Electroweak era. - Inflation. (**) - Production of matter-antimatter pairs : emergence of matter (**) -- From the first second to the first billion years - The formation of basic elements: (H, He, Li) nuclei (**) - Universe transitions from radiation-dominated to matter dominated - Recombination epoch : Universe transitions from opaque to transparent (**) - The dark ages - The formation of the first luminous objects: stars and proto-galaxies, - The reionization era -- The cosmic microwave background : Its importance and how it is observed (**) -- Evidence for the Big Bang model and for Inflation. -- The critical density of the Universe and its fates MATH AND FORMULAS ----------------- You will not be asked to do any explicit calculations, and you will not need a calculator for this exam. However, I do expect you to know how important quantities relate to each other. For instance, I expect you to know that flux will decrease if the luminosity decreases or if the distance increases because flux is proportional to luminosity and inversely proportional to the square of distance. The only 4 relations you need to know are - The flux received from any object is proportional to (Luminosity of object)/Distance^2 - The luminosity of a star on HR diagram is proportional to (Radius)^2 (Surface Temperature)^4 - The main sequence lifetime of a star is proportional to 1/(Stellar Mass)^3 - Wien's Law: The wavelength where the intensity of a blackbody or thermal spectrum peaks is proportional to 1/(Surface Temperature)