Astronomy 1001/1005 Midterm (00 points) Name: Instructions: Mark your answers on this test AND your bubble sheet You will NOT get your bubble sheet back One page of notes and calculators are allowed Use a # pencil on the bubble sheet. Make your bubbles dark and neat. There are 30 multiple choice problems, quantitative questions, and short answer questions with point values given for each. Multiple Choice (4 points each) 1) Who first found irrefutable observational evidence that disproved the theological idea that all heavenly bodies must be perfect and spherical? d a) Kepler b) Aristotle c) Aristarchus d) Galileo e) Copernicus ) An astronomical unit (AU) is: a) the Moon s average distance from Earth b) any large astronomical distance. c) Earth s average distance from the Sun. d) any planet s average distance from the Sun. e) None of the above c 3) The frost line is: a) In the Oort cloud. b) In the Kuiper belt. c) Between Saturn and Uranus. d) Between Mars and Jupiter. e) None of the above. d
4) Differentiation is responsible for: b a) magnetic fields b) heavier elements sinking to the cores of terrestrial planets c) the difference between asteroids and comets d) the creation of the two very different types of planets e) None of the above 5) When we see Jupiter going through a period of apparent retrograde motion, it means: b a) Jupiter is temporarily moving backward in its orbit. b) Earth is passing Jupiter in its orbit, with both planets on the same side of the Sun. c) Jupiter and Earth must be on opposite sides of the Sun d) Jupiter must be on epicycles e) Jupiter cannot have formed like the other Jovian planets 6) Earth is closer to the Sun in January that in July. Therefore, according to Kepler s second law, a) Earth travels faster in its orbit around the Sun in July than in January. b) Earth travels faster in its orbit around the Sun in January than in July. c) It is summer in January and winter in July. d) Earth travels the same speed all year e) F=ma b 7) If you drop a feather and a bowling ball at the same time in a vacuum, which will hit the ground first? a) the bowling ball b) the feather c) they will hit at the same time d) neither will hit the ground e) It depends on the gravity of the planet on which you conduct the experiment
8) The Moon s phases are due to: d a) the Moon rotating b) the Moon growing and shrinking each month c) shadows cast by the Earth on the surface of the Moon d) the amount of sunlight reflected from the Moon s surface to Earth, depending on the Moon s position in its orbit around Earth e) none of the above 9) Compared to its angular momentum when it is farthest from the Sun, Earth s angular momentum when it is nearest to the Sun is c a) a lot greater. b) a little greater. c) the same. d) a little less. e) a lot less. 10) A star whose spectrum peaks in the infrared is a) hotter than our Sun. b) cooler than our Sun. c) larger than our Sun. d) more massive than our Sun. e) just like our Sun b 11) The set of spectral lines that we see in a star s spectrum depends on the star s a) atomic structure. b) temperature. c) mass. d) chemical composition. e) rotation rate. d
1) About how old is the solar system? a) 4.5 thousand years b) 4.5 million years c) 4.5 billion years d) 4.5 trillion years e) as old as the Universe 13) In general, what kind of terrestrial planet would you expect to have the thickest lithosphere? d a) a planet close to the Sun b) a planet far away from the Sun c) a large planet d) a small planet e) Only Jovian planets have lithospheres 14) What do we conclude if a planet has a lot of impact craters? a) The planet is currently being bombarded by asteroids or comets. b) It has no atmosphere. c) It must be from outside our solar system. d) It is not geologically active. e) It must not have a strong magnetic field. d 15) Why is Jupiter denser than Saturn? a) They are the same mass, but Jupiter has a smaller radius. b) Jupiter is made of heavier material than Saturn. c) Jupiter is more compressed by the Sun s gravity. d) Saturn is puffed up by tidal interactions. e) Jupiter s higher mass and gravity compress its interior more. e
16) Why does Neptune appear blue and Jupiter red? a) Neptune is covered with liquid water. b) Neptune is hotter, which gives bluer thermal emission. c) Methane in Neptune s atmosphere reflects blue light. d) Methane in Neptune s atmosphere reflects red light. e) Neptune s air molecules scatter blue light, much like Earth s atmosphere. 17) Jupiter nudges the asteroids in the asteroid belt through the influence of a) tidal forces. b) Jupiter s unusually eccentric orbit. c) orbital resonances. d) the Jovian wind. e) magnetic fields. 18) Why do sunspots appear darker that their surroundings? a) They block some of the sunlight from the photosphere. b) They emit only X-Rays. c) They are too hot and got burned. d) They do not emit any light. e) They are cooler than their surroundings. e 19) The sky on Earth is blue because: a) the sky reflects the color of the ocean. b) the atmosphere emits blue light. c) blue light scatters more easily than red light. d) the atmosphere absorbs all of the colors except blue. e) none of the above
0) Which have the most elliptical and tilted orbits? e a) Terrestrial planets b) Asteroids c) Jovian planets d) Kuiper belt comets e) Oort cloud comets 1) Red light: a) has a shorter wavelength than orange light. b) has more energy than blue light. c) travels faster than yellow light. d) has a higher frequency than green light. e) none of the above e ) Which of the following worlds has the most substantial atmosphere? a) Mercury b) Venus c) Earth d) Moon e) Mars b 3) If we observe the spectral lines of a galaxy moving toward us, the lines will: a) look brighter than usual. b) look dimmer than usual. c) look redder than usual. d) look bluer than usual. e) be unchanged. d
4) Which of the following is NOT an acceleration? a) a greyhound running around a track at a constant 35 km/hr b) you slowing down your car at a stop sign c) sliding across frictionless ice in a straight line d) a bowl of soup falling to the floor e) the Moon orbiting around the Earth 5) The color of the stripes on Jupiter can tell us what about the stripe? a) its temperature b) its altitude c) its composition d) all of the above e) none of the above d 6) Why is Io more volcanically active than our own Moon? a) Our own Moon was cooled by impacting the Earth. b) Io is larger than our Moon. c) Io is tidally heated by Jupiter. d) Io has more radioactive metals. e) Io isn t volcanically active. c 7) Why isn t Pluto defined as a planet? a) It is too small. b) It is not round. c) It has not cleared its orbit of debris. d) It is too far from the Sun. e) Scientists are mean.
8) How do asteroids differ from comets? d a) Asteroids are made of mostly icy material while comets are made of rocky material. b) Asteroids and comets are both made of rocky and icy material, but asteroids are larger. c) Asteroids and comets are both made of rocky and icy material, but comets are larger. d) Asteroids are made or rocky material, and comets are made of mostly icy material. e) Asteroids are made of metals while comets are made of mostly rocky material. 9) What two forces are balanced in gravitational (hydrostatic) equilibrium? a) The electromagnetic force and gravity b) Outward pressure and the strong force c) Outward pressure and gravity d) The strong force and kinetic energy e) The strong force and gravity 30) By what process do stars generate energy? a) Nuclear fission b) Nuclear fusion c) Chemical reactions d) Gravitational contraction e) Burning coal b
Quantitative Questions (0 points each) The comet Hale-Bopp has an aphelion distance of 371 AU and a perihelion distance of 1 AU; therefore, Hale-Bopp s average distance from the sun is 186 AU. Using Kepler s third law, find the orbital period of Hale-Bopp? p a p a 3 3/ 186 3/ 536.7 yrs Using Newton s version of Kepler s third law and the orbital period and average distance of Hale-Bopp, calculate the mass of the Sun. (Hint: be careful with units: m, kg, sec) a = 186 AU = 186 AU * 1.5*10 11 m/au =.79*10 13 m p = 536.7 years = 8*10 10 sec p 4 G( M M Sun HB a ) 3 M Sun +M HB M Sun M Sun 3 4 a 4 (.7910 11 3 1 Gp (6.67 10 m kg s 3 m) )(8 10 13 10 s) 41 3 8.6 10 m 11 3 4.7 10 m kg 1 10 30 M Sun
Short Answer Questions (0 points each) Describe the two most important properties of a telescope. Explain what they mean and why they are important. The most important property of a telescope is its collecting area or the size of its objective lens. The only information we get in astronomy comes from light, so the more light we can collect the better, and a bigger lens allows us to collect more light. The second most important property is its angular resolution. The angular resolution is the smallest angular separation that two point-like objects can have and still be seen as distinct objects rather than one smeared-together-looking object. Smaller is better. Please explain how the greenhouse effect works. Use words and a diagram. The sun emits visible light, which has no trouble passing right through the greenhouse gasses in the atmosphere. The visible light reaches the ground, providing energy and heating it up. Everything with thermal energy emits light, so the ground, which is heated to about 300K, emits IR light. The greenhouse gasses trap the IR light in the atmosphere. The atmosphere then reradiates that light, much of which comes back to the surface, heating it a little further. The constant incoming visible light and the trapped IR light combine to continually heat the surface.