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Astro 10 Final Review This final review sheet is meant to be a fairly rough study guide for what I think are the important topics from Midterm 1 onward. I suggest using this review sheet as a way to gauging how well you understand the material. I also STRONGLY recommend going over the practice final on page 121 of the course reader and the multiple choice review questions at the back of each chapter of the book (solutions are on bspace). I would also suggest going over the homework and the midterms as a way to review past material. The final tends to be fairly tough so study hard! Good luck! True or False 1) A star which appears blue is hotter than a red star because of the Doppler shift. 2) For two stars in a binary orbit, the center of mass will be closer to the more massive one. 3) If the distance between the Sun and the Earth increased by a factor of 2, the Sun’s luminosity would decrease by a factor of 4. 4) Pre-main sequence stars release energy by nuclear reactions which turn hydrogen into helium. 5) Astronomers can determine the age of clusters by looking at the distribution of stars on the main sequence. 6) A brown dwarf is a type of dark matter called a WIMP. 7) Our Sun will one day end up a white dwarf. 8) Supernova 1987A was a Type II core collapse supernova which was the result of the collapse of a black hole. 9) All neutrons stars with magnetic fields will form pulsars. 10) It is possible for light to orbit a black hole inside the black hole’s Schwarzschild radius. 11) Your best bet in surviving a black hole would be to approach a really really large black hole. 12) Harlow Shapley used open clusters in our galaxy to determine that our Solar System of not the center of the galaxy. 13) Our galaxy’s flat rotation curve implies the existence of dark energy in the form of elementary particles called WIMPs. 14) Quasars are galaxies which emit huge amounts of energy in a small amount of space through nuclear fusion. 15) The expansion of the universe implies the distance between the Earth and the Moon is increasing. 16) Gravitational lensing of very distant galaxies by galaxy clusters has been used as evidence for the existence of dark energy. The Sun and Stars 1) Draw an HR diagram with the main sequence. Be sure to label axes. 2) What is hydrostatic equilibrium? 3) Where in the star does fusion take place? (Hint: Where in a star do you think it is the hottest?) 4) List the spectral types from hottest to coolest. What type of star is the Sun? This usually shows up in the exam in some form or another. 5) How does one determine the age of clusters? 6) Star Mark Walberg is 16 times as luminous as Star Donny Walberg. How much older is Donny? Assume both are main sequence stars. Recall L ∝ M 4 . 7) What is the main fusion reaction that powers stars while on the main sequence? 8) What is a red giant? Will the Sun ever become one? What will we observe from Earth? 9) You observe a star with a parallax of .200 . How far away is this star? 10) There are basically two different type of supernovae (SNe): Type Ia and core collapse (which includes both Type II and Type Ib/c). In each case, what is the progenitor star, what produces the SN, and what is left after the explosion. 11) What are sunspots? Why do they appear dark? 12) What is the period of the sunspot cycle? 13) What is the photosphere? The chromosphere? Galaxies, Crazy Quasars, and Black Holes 1) Are you more likely to see a Type II supernova in a spiral galaxy or an elliptical galaxy? What about a Type Ia? 2) Where would you find open clusters in a spiral galaxy? Globular clusters? 3) How did pipe enthusiast and astronomer Edwin Hubble determine the distance to other galaxies? What relationship did he find when he looked at his data? Does this relationship change with time? 4) How are quasars related to active galactic nuclei (AGN)? 5) How can quasars be used to probe the material between us and the quasar? 6) What is the ”photon sphere” of a black hole? How is it different than the event horizon? 7) Stanfurd sucks. Say you were to throw a stanfurd student wearing a red jacket into a black hole and watch the spectacle from a safe distance away. Would you be able to see him fall into the blackhole? What color would his jacket appear as he got closer to the event horizon? 8) If Edwin Hubble were to have based his conclusions of the expansion of the universe off of observations of the Andromeda galaxy, what would he have concluded? Cosmology 1) If light traveled at an infinite speed, what would the night sky look like? 2) What is Olber’s Paradox? What is its solution? 3) What is the cosmological principle? 4) A not so smart stanfurd student (will they ever learn?) claims that the universe had no beginning and that it will have no ending. She believes that in the steady-state universe hypothesized by Fred Hoyle. What evidence could you use from Astro 10 to prove this ignoramus wrong? Come us with at least two pieces of evidence. 5) What properties of type Ia supernovae have made them of particular importance to cosmology? How were type Ia supernovae used to conclude that the universe is accelerating? How is this acceleration explained? 6) What is the Cosmic Background Radiation (CBR)? Why can’t we see any other electromagnetic radiation before the CBR? Why do we detect temperature fluctuations in the CBR? 7) Oh the Universes you will see... I strongly encourage everyone to look over problem 2 on the cosmology worksheet to get an idea of the possible geometries for the universe depending on the value of Ω. Now imagine an Astro C10 student falls through a worm hole that amazingly transports said student to a 2-dimensional universe. Wanting to make the most of her new universe, she decides to explore her new home universe. After walking for a few hours she finds that she ended up at her starting point! If she were to draw a triangle in her universe, what would the angles add up to? What type of universe does she live in? 8) What are two problems with the original big-bang model? What theory has been proposed to explain these problems and how does it do so? 9) What is the significance of the Planck time (∼ 10−43 s) in the context of the Big Bang? In other words, what was the universe like before it and after it?