legible name _____________________________________ Astro 203, Section 1, spring 2001, FINAL EXAM Olszewski and Bailin Please ensure that your name is on this paper, the SCANTRON, and on your ``cheatsheet''. The cheatsheet needs to be handed in with the exam. We have staplers. There is one best answer for each question. The context of each question is this Astro 203 class. The use of context is a good thing. There are 60 questions on 9 pages. Please ensure that you have a complete exam. Look on the blackboard for corrections as they might appear. You may raise you hand to ask questions of clarification. We will answer them if we can. 1) Approximately what year did we realize that stars are shining because of nuclear fusion? a) 1630 b) 1730 c) 1830 d) 1930 2) Approximately what year did we realize that stars have created most of the elements? a) 1650 b) 1750 c) 1850 d) 1950 3) Approximately what year did we measure the first parallax of a star? a) 300BC b) 170AD c) 1609 d) 1840 e) 1950 4) How do we know the luminosities of ``nearby'' stars? a) Doppler shift b) Parallax c) Emission lines d) Gravitational Redshift 5) A first magnitude star is xxx times as bright as a 6th magnitude star? a) xxx = 100 b) xxx = 1/100 c) xxx = 5 d) xxx = 1/5 6) One of these types of stars actually can be seen to evolve by humans (ie, in one human lifetime or less) a) Massive main sequence star b) Low mass main sequence star c) Red giant d) Supernova 7) How do you weigh stars? (actually make the measurement) a) Orbital characteristics of a binary star b) Strengths of spectral lines c) Proper motion d) Kirchoff's laws e) Parallax 8) Why does the Sun NOT get very much of its energy from the CNO cycle? a) it's still collapsing b) it's not hot enough c) it doesn't have any C, N, or O d) too much hydrogen 9) Think of a simple 3-level atom. the electron can be in the lowest energy state, or 10 energy units above the lowest state, or 15 energy units above the lowest state. The gas is cold, so all of the electrons are in the lowest orbit. We shine light of energy ``10 energy units'' into a gas of these atoms. Does this light get absorbed? a) yes b) no 10) Same as question 10 except we shine light of 12 energy units onto it. Does this light get absorbed? a) yes b) no 11) There is a way to make elements called the R-Process. In what sort of stars does the R-Process operate? a) Main Sequence stars b) Red Giants c) Supernovae d) White dwarfs e) Pulsars 12) There is a way to make elements called the S-Process. In what sort of stars does the S-Process operate? a) Main Sequence stars b) Red Giants c) Supernovae d) White dwarfs e) Pulsars 13) What would be the analogy to the ``Chandrasekhar limit'' for neutron stars (as opposed to the real Chandrasekhar limit for white dwarfs)? a) the mass limit at which no fusion happens b) the mass limit at which a neutron star cannot be a pulsar c) the mass limit at which a remnant would become a black hole d) the mass limit at which radiation pressure destroys a main-sequence star 14) Imagine a white dwarf right at the Chandrasekhar limit. Now imagine a neutron star a teeny bit above the Chandrasekhar limit. The white dwarf is made of up protons and neutrons and electrons. The neutron star is made up of neutrons, with few electrons and protons. Where did all of the electrons and protons go? a) Mass loss spewed electrons out into the universe. b) More fusion got rid of the protons c) The electrons were forced into the atomic nuclei where they combined with protons to make more neutrons d) The electrons fused together to make helium 15) If you want to see a star early in the process of forming (protostar), what sort of light should you collect, and why? a) optical; all stars give off optical light b) ultraviolet; higher energy light penetrates the gas and dust better c) infrared and radio; this light is less affected by dust absorption d) xray; xrays can look inside of humans, right? 16) A black hole gives off no light (ignore the accretion disk). A planet gives off no light (that's not completely true, but it's not bad). So, if you're monitoring the wavelengths of spectral lines in a star that's orbiting one of these two objects at a distance of 5AU, how do you tell whether the regular star is orbiting a black hole or a planet? a) It must be a planet. If the star is orbiting a black hole it would get sucked into the black hole and destroyed. b) It must be a black hole. We can't find extrasolar planets. c) A star orbiting a black hole at a distance of 5AU will be orbiting much more quickly than a star orbiting a planet at a distance of 5AU. d) We simply cannot tell the difference. 17) Why haven't we found any extra-Solar Earths orbiting other stars? a) The technology simply isn't yet good enough. b) We have proven by our discoveries of extra-Solar planets that extra-Solar Earths simply don't exist. c) The Earth's oxygen and carbon dioxide absorbs all of the light. d) The Earth is a rocky planet, not a gaseous planet. 18) Why does the Earth's atmosphere have little Carbon Dioxide? a) It's all hidden in the oceans and in rocks. b) It all escaped because of the Earth's low gravity. c) It was all converted into rust. d) Our carbon dioxide now resides in Venus. 19) Why is it so interesting that Mars might still have some liquid water occasionally on its surface? a) Mars must have once been a moon of Jupiter. b) If Mars doesn't have water, then the Earth shouldn't. c) If there ever were life on Mars, it might still exist. d) Water is needed to preserve fossils. 20) There is a sketch of an H-R diagram on the screen. Which letter corresponds to a T-Tauri star and why? a) A or B. T-Tauri stars are cooler and more luminous than the main-sequence star that they will become. But they aren't super-red because they've lost their dust shrouds. b) C. The T-Tauri phase refers to the beginning of stable hydrogen burning. c) D. T-Tauri stars are intrinsically very faint. d) E. T-Tauri stars are hotter than main seqeunce stars because of Kelvin- Helmholtz contraction. e) F. T T-Tauri stars are very luminous. 21) There is a sketch of an H-R diagram on the screen. Which letter corresponds to a red giant and why? a) A or B. Red giants have changed their original main-sequence structure and are now redder and more luminous than the star from which they evolved. b) C. Red giants fall somewhere on the DCF line. c) D. Red giants are red, which means to the right of this diagram. d) E. Red giants are luminous. Hot stars are luminous and they're to the left in this diagram. e) F. Red giants are luminous, and high luminosity is up in this diagram. 22) Think about objects that radiate like blackbodies. Bluer objects are hotter than redder objects. This fact is quantitatively dealt with in a law called xxx. a) xxx = Doppler effect. b) xxx = Redshift c) xxx = Stefan-Boltzman law d) xxx = Wien's Law e) xxx = Chandrasekhar limit 23) We don't see pulsars in the center of all supernova remnants. Why not? a) Not all pulsars have their beams pointing at Earth. b) Not all supernovae leave behind compact remnants. c) Some supernovae leave behind white dwarfs. d) Some of those ``supernova remnants'' are really star-forming regions. e) a and b 24) In protostellar evolution, the collapse of the central object slows down for a while due to which fusion reaction? a) Hydrogen burning (the proton-proton cycle) b) the CNO cycle c) the R Process d) the S Process e) Deuterium burning 25) What is the ultimate Holy Grail for the proposed Terrestrial Planet Finder spacecraft, due to be launched in about 10-15 years? a) to find an Earthlike planet. b) to find an Earthlike planet in the habitable zone of its star. c) to find oxygen lines in the spectrum of an Earthlike planet in its habitable zone. d) to find planets orbiting pulsars. e) to find life on Mars. 26) If you're inside an ``elevator'', can you tell if you're sitting quietly on the surface of the Earth, or if you're in space being accelerated ``upwards''? a) yes b) no 27) As you get closer and closer to the event horizon of a black hole, you... a) Notice no change because the event horizon is not a physical surface. b) Notice (at least while you're still alive) that you're being stretched from head to toe, and compressed perpendicular to that. c) Notice that not all of the clocks in your rocketship are keeping the same time. d) Discover that you are travelling backwards in time. e) Notice that you're emitting vast amounts of Hawking radiation. 28) If the Sun were magically replaced by a 1-solar-mass black hole, what would happen to the Earth's orbit? a) The Earth would spiral into the black hole and disappear. b) The orbit would change because a black hole is not the same size as a star. c) The orbit would not change because we are still being tugged on by a 1-solar-mass object 93 million miles away. d) The orbit would change because black holes tug harder on other matter than do stars. 29) What's the easiest way to find a black hole, a neutron star (not a pulsar), or a white dwarf? a) Look with your naked eye. They're all bright. b) Look at the catalog of nearest stars. There are no faraway black holes, neutron stars, or white dwarfs. c) Look at variable x-ray sources. They are possibly black holes or neutron stars or white dwarfs in orbit about normal main sequence stars or red giants. d) Look at empty places in the night sky. 30) Why don't we notice, in everyday life, that General Relativity is needed to describe nature? a) Newton's Laws work just fine except when gravity is very strong. b) We use General Relativity all the time. We just call it by a different name. c) General Relativity only applies in freely falling elevators. d) General Relativity has to do with atoms. We can't see atoms. e) The Heisenberg Uncertainty Principle washes out the effects of General Relativity on 1cm scales. 31) Imagine light from a distant star passing very close to the surface of the Sun. According to General Relativity AND to observation, what happens to this light? a) It travels in a straight line just like all light. b) It follows a curved path when it's near the Sun. c) It vanishes because of the Schwarzschild radius of the Sun. d) It becomes blue shifted. 32) What object lights up a planetary nebula? a) external stars b) neutron star ``core'' of the original star c) white dwarf ``core'' of the original star d) fusion of the hydrogen in the planetary nebula. 33) We asked you to read Jocelyn Bell's recollections. What did she say about NOT getting a Nobel Prize for the discovery of pulsars while her dissertation advisor did? [this might be different from what Dr Olszewski said HE thought.] a) She said that she had the prize stolen from her. b) She said that she didn't think that students should get Nobel Prizes except under the most special circumstances. c) She said that someday, when someone actually does get a Nobel Prize for pulsars, that she was sure she'd get one. d) She said that since pulsars were white dwarfs, she'd discovered nothing especially new. e) She said that the Nobel Prize Committee couldn't track her down because she changed her last name when she got married. 34) What is a ``shooting star?'' a) A real star suddenly brightening and then fading away. b) A piece of comet dust crashing into the Earth's atmosphere and burning up because of friction. c) A black hole vanishing because of Hawking rdiation. d) A comet ``sweeping across the sky.'' 35) Why do we think Halley's comet is in its current 76-year orbit? a) Gravitational interactions with the big planets has changed its orbit. b) It's always been in that orbit. c) It crashed into the Sun once. d) Collision with another comet. 36) Even though a main sequence star is ``pretty darn stable'' over its lifetime, why does it actually slowly change its luminosity during its main sequence lifetime? a) Collisions with other stars. b) It cleared out the disk out of which the planets were made. c) The fusion reactions that turn H --> He reduce the number of particles in the core. To keep the same pressure the temperature must go up in the core. d) As the star ages, the outer layers of the star push inwards harder. 37) What's the difference between ``luminosity'' and ``apparent brightness''? a) Apparent Brightness is how much light leaves the star every second. Luminosity is what we measure here on Earth. b) Luminosity is how much light leaves the star every second. Apparent Brightness is what we measure here on Earth. c) Luminosity has to do with the color of the star while apparent brightness has to do with the total energy leaving the star. d) None. Both of these measure what ``hits our eyeballs'' here on Earth. 38) If we had a telescope on Jupiter (ignore that Jupiter doesn't have a solid surface), would we measure a larger or smaller parallax for star X than we do using telescopes confined to Earth? a) Larger. The baseline (size) of Jupiter's orbit is larger. b) Smaller. The baseline of Jupiter's orbit is larger. c) Neither. Parallax is proportional to distance and the distance hasn't changed. d) It's hard to figure out because Jupiter is much closer to star X than the Earth is. 39) ABOUT how many AUs away is the nearest star? a) 1 b) 100 c) 5000 d) 250000 e) many million 40) What is the Fermi Hypothesis for intelligent life in the Universe? a) If a civilzation chose to colonize the Milky Way, they could do it in a small amount of time compared to the age of the Milky Way. So where are they? b) Civilizations don't live for long because they blow themselves up. c) Not all stars have planets in the habitable zone. d) Not all species develop ``radio telescopes''. e) If an intelligent civilization were to tap the energy stored in a black hole, then they could colonize the Milky Way very quickly. 41) What is the context from Astro 203 in which we diverted ourselves to a discussion of Tuvan Throat Singing? a) We never discussed such a concept. b) Intelligent Life- it'll probably be hard to understand an alien civilization. c) Helioseismology- the Sun rings like a bell so we can derive its structure from how it rings. d) Black holes- this is how Hawking Radiation works. 42) There is a special place in the sky called THE ECLIPTIC. What is it? a) The apparent path of the Milky Way in the sky. b) The apparent path of all stars in the sky. c) The apparent path of the Sun and Moon and planets in the sky. d) The apparent path of comets in the sky. 43) Why are the lengths of a siderial day and a solar day different? a) Light from the stars takes a long time to get to the Earth, making a siderial day longer than a solar day. b) The Moon's orbit confuses this whole picture. c) Because the Earth is going around the Sun it has to rotate a bit more than 360 degrees to line up with the Sun each day, making the solar day longer than the siderial day. d) Precession of the equinoxes changes the length of the days. 44) What's special, perhaps even magic, about the constellations of the zodiac? a) They control your life. b) Nothing. they're just star patterns aligned with the plane of the Solar System. c) The Moon is always the same phase in the same constellation. d) They are all in the plane of the Earth's equator. 45) Why would several cultures have adopted the idea of a LUNAR ZODIAC? a) They wouldn't. The constellations are not human constructs, but are actual important places in the heavens. b) The moon is more important to life than is the Sun. c) Why would they? The moon doesn't follow the zodiac anyway. d) Why not make 28 constellations along the ecliptc to track the nightly motion of the Moon? 46) What was Aristotle's best argument that the Earth could not possibly go around the Sun? a) If the Earth were moving it would always be windy. b) He didn't see stellar parallax. c) What could ever have set the Earth in motion? d) Water always flows in rivers to the south. 47) Which of the following names is a Bayer name? a) 51 Peg b) Alpha Centauri c) HD 122563 d) QSO J005109-4226.5 48) Which of the following are NOT electromagnetic waves? a) Visible light b) X-Rays c) Gamma Rays d) Microwaves e) They all are! 49) What causes an absorption line in the spectrum of a star? a) The continuous spectrum made by the hot, dense interior of a star passes through a cooler, thinner gas which absorbs some of the light. b) It has to do with the light made in the fusion reactions in the core. c) The S-Process. d) The escape of neutrinos. 50) Why did Tycho's careful observations of a supernova help to overthrow the Ptolemaic system as interpreted by the Catholic Church? a) The heavens were shown to change. b) Supernovae (Tycho didn't know what they were) were shown to be orbiting the Sun, not the Earth. c) Kepler used these observations of the supernovae to derive what are now known as Kepler's Laws. d) He killed someone, who didn't believe in supernovae but did believe in the Ptolemaic view, in a duel. 51) If we scale the Sun so that it's the size of a grapefruit, how far away is the nearest star? a) 2000 miles b) 50 feet c) 5 feet d) 0.5 feet 52) We think [correctly] of the Cepheid Period-Luminosity relation as saying, ``the longer it takes a Cepheid to pulsate, the brighter it is intrinsically.'' The person who discovered the P-L relation actually might have said something like ``for Magellanic Cloud Cepheids, the longer it takes to pulsate, the brighter it is as seen from Earth.'' How can we reconcile these two quotations? a) Henrietta Leavitt was simply wrong. The second quotation has errors of fact. b) All of the Cepheids she measured were at the same distance from Earth, so an instrinsically brighter star is also apparently brighter. c) There are actually two P-L relations for Cepheids, one for the Magellanic Clouds and one for everywhere else. d) She didn't measure Cepheids, she measured the brightness changes of Mira variables. 53) Was the center of the Sun hot before fusion started? Why/why not? a) No. Fusion provides the energy to heat the core. b) Yes. The center of the Sun must be hot to hold it up against gravity. c) No. Fusion starts at low temperature, then creates high temperatures. d) Yes. Any spinning object is hot. 54) When you measure the age of Moon rocks and of meteorites, you get about 4.5 billion years. Why would we care about this number in a course called ``STARS''? a) All of the stars in the sky must be about this age. b) No stars in the sky can be older than the Sun. c) It tells us how many years must pass, from today, till the Sun becomes a red giant. d) We need to explain how the Sun has had its luminosity for such a long period of time. 55) Why is the fact that massive main sequence stars live only 1-10 million years interesting in the context of this class? a) One million years is a tiny fraction of the age of the Sun. Stars must therefore be born even now. b) We can calculate how many years are left until stars can no longer be born. c) It allows us to calculate the spin-down rate of pulsars. d) It explains when the Sun was born. 56) Why did we discuss ``the drunkard's walk'' in the context of energy loss by radiation in the Sun? a) It's how a star ``moves'' on the HR diagram. b) It's how convection works. c) Photons created in the center of the Sun are absorbed and reradiated countless times before they make it to the surface of the Sun. d) As uranium particles are split apart they emit neutrons which go off in random directions. 57) If we want to understand energy generation in the core of a star, why might we want to look at the surface abundances of the elements in a cool star with a very deep surface convection layer? a) They explain the mass-luminosity relation. b) Those stars bring the products of fusion to the surface layers of the star. c) Energy generation cannot take place without convection. d) The elements in the surfaces of all stars are made in the interiors of those same stars. 58) A few years back the Quebec hydroelectric system collapsed for eight hours, costing more than 100 million dollars, because of... a) a supernova. b) a nova. c) a solar storm. d) a volcano. e) the equinox. 59) Wouldn't it be nice to be able to see sunspot cycles in other stars? Well, we can. How? a) Young stars spin fast. b) Changes in the Earth's atmosphere by such cycles in other stars. c) Certain spectral lines are enhanced in sunspots. d) We have sent picture-taking satellites to other stars. 60) What is the Main Sequence? a) The evolutionary path of a single star. b) A sequence of core helium burning stars. c) The locus of core hydrogen burning stars. d) White dwarfs.