ASTR1070_ModuleExamII_FormA

Form A ASTR:1070 Stars, Galaxies and the Universe Module II Exam Prof. Casey DeRoo Nov. 1 st , 2023 1:30 – 2:20 pm

1.) The “main sequence turnoff” of a cluster can be used to determine: a. The distance to the cluster b. The total mass of the cluster c. The total luminosity of the cluster d. The chemical composition of the cluster e. The age of the cluster 2.) Which of is NOT a fundamental characteristic of a black hole? a. Electric charge b. Chemical composition c. Mass d. Angular momentum / spin e. This question is wrong -- these are all fundamental characteristics of black holes 3.) When measuring stellar parallax, how can we maximize the observed change in angle of the star relative to the background of fixed (i.e., very distant) stars? a. Measure the position of the star multiple times over the course of a single night b. “Crowdsource” measurements of the same star from all of over the globe c. Measure the same star at different wavelengths d. Measure the star in opposite seasons (e.g., summer/winter) e. Measure the star on the same calendar day for millennia 4.) Fill in the blank: massive stars on the main sequence are ________ in color and ________ our Sun. a. Redder; more luminous than b. Redder; about the same luminosity as c. Bluer; more luminous than d. Bluer; less luminous than e. More colorful; more luminous than 5.) What is the primary characteristic that makes Cepheid variable stars important in astronomy? a. They are the smallest stars in the universe b. They have highly eccentric orbits c. They are the most common type of star in our Milky Way galaxy d. They exhibit a regular and predictable variation in their brightness which is related to their luminosity e. They are the hottest stars, emitting intense ultraviolet radiation and creating HII regions 6.) A molecular cloud fragments as it collapses because: a. the density increases fastest in the center of the cloud b. density variations from place to place grow larger as the cloud collapses c. the interstellar wind is stronger in some places than others d. the rotation of the cloud throws some mass to the outer regions e. molecules release energy through chemical burning, causing the cloud to evaporate 7.) As high mass stars leave the main sequence, how do they evolve? a. They shrink, moving them to the lower left of an HR diagram b. They increase substantially in luminosity, moving them directly upwards on the HR diagram c. They get hotter and bluer, moving them leftwards on the HR diagram d. They grow cool and less luminous because they’ve run out of elements to fuse, moving them down and to the right on the HR diagram e. They remain about the same luminosity but change size and temperature, moving them left and right on the HR diagram

b. O5, G2, A5, K5 c. A1, A0, M6, K9 d. B0, A5, K8, O5 e. A4, G2, M5, A9 16.) In astronomy, interstellar extinction refers to: a. Stars burning out and being extinguished throughout the galaxy b. Localized gamma-ray bursts that could potentially wipe out habitable civilizations c. The quenching of star formation after a period of time d. The wiping out of 50% of all life with a snap of the fingers, Thanos-style e. The absorption of some light by dust grains, resulting in “redder” light 17.) Which of these phases of the ISM are associated with H α emission from excited hydrogen? a. Molecular Clouds b. Cold Intercloud Gas c. Warm Intercloud Gas d. Hot Intercloud Gas e. Planetary atmospheres 18.) A pulsar pulses because: a. Its magnetic axis crosses Earth's line of sight b. It is in an orbiting binary, causing the star to go in and out of the shadow of its companion c. It is changing temperature due to the release of energy from fission d. It is regularly growing and shrinking in size e. Fusion turns off and on rapidly due to its high density 19.) If we found that hydrogen in another galaxy produced a different set of emission lines than it does on Earth, what scientific principle would this undermine? a. Occam’s Razor b. Special Relativity c. Cosmological Principle d. Kepler’s 2nd Law e. Newton’s Theory of Gravity 20.) The Hayashi track is a nearly vertical evolutionary track on the H-R diagram. What does the vertical nature of this track tell you about a protostar as it moves along it? a. The star remains the same size b. The star remains the same luminosity c. The star remains the same brightness d. The star remains the same color e. The star remains the same age 21.) What do all stars on the main sequence have in common? a. They all have a mass of less than 3.0 M Sun b. They all have a photosphere with temperatures < 10,000 K c. They all go through 11-year solar cycles in which their magnetic fields flip d. They all are fusing H into He in their cores e. They all are undergoing mass loss to the ISM 22.) The Sun is made mostly of what element? a. Iron b. Magnesium c. Helium d. Hydrogen

e. Carbon 23.) Figure 2 shows a low mass star after leaving the main sequence. What are the outer layers shown in red and green? a. Oxygen and silicon metals blown out from the star’s final fusion processes b. The outer layers of hydrogen being shed from a asymptotic giant branch star, forming a planetary nebula c. Nitrogen boiling off from planets as the star gets really bright d. The heavy metal ejecta from a Type II supernova explosion e. Molecular hydrogen left over from the large dust cloud fueling the star’s formation 24.) Figure 2 shows a low mass star after leaving the main sequence. What stage of stellar evolution is the bright, blue point-like object in the center of the image? a. A white dwarf b. A horizontal branch star c. A protostar d. A neutron star e. A black hole 25.) What is the heliosphere? a. The outermost region of the Sun’s atmosphere where prominences are common b. The “zone of influence” of the Sun where the solar wind is balanced against the pressure from the ISM c. A unit of measurement equal to a sphere the size of the Sun d. A fictional sphere surrounding a star like our Sun collecting all its energy e. The portion of Earth being illuminated by the Sun at any one time 26.) Fill in the blank: the proton-proton chain converts ____________ into ____________. a. One proton; energy and gamma rays b. Temperature in the core; pressure via the strong force c. four H nuclei; one He-4 and energy d. Six H nuclei; one C nucleus and infrared radiation e. Protons and electrons; neutrinos and antimatter 27.) Which of the following is the root cause of a Type II supernova? a. Two white dwarfs in a binary star system combine, exceeding the Chandrasekhar mass b. The merger of two neutron stars c. The impact of a comet or asteroid on a planet d. Neutrinos build up in the core because they are unable to escape while the star is fusing e. A massive star fuses elements until building up iron in the core, which no longer yields energy when fused 28.) In Figure 3, a spaceship approaches the Earth at half the speed of light (0.5c). If it turns on a laser, how fast does the observer on Earth see the laser light moving? a. 2x the speed of light (2c) b. 1.5x the speed of light (1.5c) c. At the speed of light (c) d. Just under the speed of light (< c) e. 0.5x the speed of light (0.5c) 29.) Which of these stars has the longest main sequence lifetime? a. A 1.1 M Sun , G0 spectral type star b. A 4.0 M Sun , B6 spectral type star c. A 0.7 M Sun , K4 spectral type star d. A 0.3 M Sun , M8 spectral type star