AST 101 - FINAL EXAM QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2026

AST 101 - FINAL EXAM QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2026 The Andromeda galaxy is 2.5 million light years away. This means that when we look at Andromeda through a telescope, the light we see - Answers shows how it looked 2.5 million years ago When viewed from Syracuse, why do the stars appear to move in circles around Polaris? - Answers Because of the Earth's rotation on its axis When viewed from Earth, which way do the stars appear to rotate around the North Celestial Pole? And which way around the South Celestial Pole? - Answers The stars appear to rotate counterclockwise about the North Celestial Pole, and clockwise around the South Celestial Pole Why does Polaris, the North star, not appear to move throughout the night? - Answers Because the Earth's axis of rotation points directly towards it Where on Earth should you stand to be able to see nearly every star rise and set during the course of a day? - Answers Equator Polaris, the North Star, always appears due north and completely stationary in the sky. What can you say about Polaris' altitude and azimuth? - Answers Polaris' altitude depend on your latitude, but the azimuth is 0 degrees. Suppose you have two observers of the night sky, one located in Syracuse (latitude 43 degrees North) and the other in Los Angeles (latitude 34 degrees North). Which of the following is true for these observers? (Hint: Draw a diagram of the observers, labeling them at their correct latitudes.) - Answers The North star, Polaris, will appear closer to the horizon for the observer in Los Angeles Suppose you see a star with an altitude of 20 degrees and an azimuth of 0 degrees. What might you say to describe the location of this star qualitatively? - Answers The star is low in the Northern sky. Suppose you are standing at 45 degrees North latitude. You see a star exactly at your zenith. Throughout a day, will this star ever set below the horizon for you? Hint: Draw a diagram of the Earth, label your location at 45 degrees North latitude, and label your zenith direction. Then think about how your view of the star will change throughout the day. - Answers No, this star will appear to just touch your North horizon What most accurately describes a day during the December solstice for an observer on the Equator? - Answers The day is exactly 12 hours long, and the Sun is found in the southern sky for the entire day For solar noon during the December solstice for an observer on the Equator, at what altitude and azimuth will you find the Sun? Hint: Draw a diagram of the December solstice, and label the observer on the Equator with a dot. Then draw the observer's horizon arrows for North and South and zenith. Finally, think about the angle you would have to look at to see the Sun. Is it in a more northern or southern direction? - Answers 66.6 degrees Azimuth: 180 degrees During an Equinox, an observer in the Southern Hemisphere observes the Sun rise directly in the East. What sort of path does the Sun take across the sky for the rest of the day? - Answers The Sun rises from the East toward the Northern sky, then back down in the West The line of the ecliptic is the path that the Sun follows on the celestial sphere each year. The line of the ecliptic is actually a circle, and when the celestial sphere is flatten it out on a graph is looks like it is moving up and down. What aspect of Earth would have to change to make the celestial equator and the line of the ecliptic line up perfectly? - Answers Earth's axial tilt would have to be zero degrees What is the important quantity that allow orbital cycles to affect the climate? - Answers - Where solar radiation is distributed on the Earth. - The amount of solar radiation the Earth receives. Time of day you would see each phase of the moon at your zenith: Full Moon - Answers Midnight Time of day you would see each phase of the moon at your zenith: Waning Crescent - Answers Just after sunrise Time of day you would see each phase of the moon at your zenith: Waxing Gibbous - Answers Just after sunset Time of day you would see each phase of the moon at your zenith: Waxing Crescent - Answers just before sunset Time of day you would see each phase of the moon at your zenith: waning half moon - Answers sunrise You see a Waxing Crescent setting in your Western horizon. What time of day is it for you? - Answers just after sunset You see a Waning Half Moon in the sky. What will the phase of the Moon be one week later? - Answers New Moon During a solar eclipse, which are responsible for the motion of the Moon's shadow across the Earth's surface? Select two of the following. - Answers - Moon's orbit - Earth's rotation Suppose there is a Waning Gibbous in the sky. During what time of day will you see neither the Sun nor the Moon? - Answers Just after sunset Gregorian - Answers Has twelve months in a year, months do not match the moon's phases, requires leap days to match the seasonal year Islamic (Hijra) - Answers Has twelve months in a year, months match the moon's phases, does not try to match the seasonal year Jewish (Hebrew) and Chinese - Answers Has twelve or thirteen months in a year, months match the moon's phases, corrects for the seasonal year by adding extra months to 7 out of 19 years Sidereal - Answers Uses the stars to keep track of time, rather than the Sun Why was Copernicus's heliocentric model preferred by some scientists at the time over Ptolemy's geocentric model? - Answers It was a simpler explanation of a complex phenomena A ______ model greatly reduced the complex epicycles introduced by ______ models What did Galileo discover with his invention the telescope? - Answers - Jupiter's largest moons - Phases of Venus - Rings or 'ears' on Saturn How was the circumference of the Earth first calculated? - Answers By using the distance between two points on the same longitude line and the difference in the Sun's angle at both points What is the true cause of retrograde motion of the planets? - Answers Planets closer to the Sun (like Mercury) passing planets further from the sun (like Earth) in their orbits Ptolemy of Alexandria - Answers This astronomer developed the most accurate geocentric model of the planets' motion in the ancient world, featuring epicycles Copernicus - Answers This astronomer conceived of the idea that the Sun is the center of the solar system, but his model was less accurate than geocentric contemporaries Brahe - Answers This astronomer took precision astronomical measurements, but still ascribed to geocentric ideas. Kepler - Answers This astronomer used the precision data on the planets' motions to determine empirical laws which were consistent with heliocentrism Galileo - Answers This astronomer developed and used the telescope to compile evidence in favor of a heliocentric model of the Solar System Newton - Answers This astronomer discovered a fundamental force of the universe, and used it to explain the motions of the planets Which of the following was NOT a reason for supporting the Copernican heliocentric model in the time of Galileo? Recall that the Copernican heliocentric model puts all the planets, including Earth, in circular orbits around the Sun. - Answers Heliocentrism was better at predicting the planets' locations In the historical process of figuring out how the planets moved, what was most valuable to astronomers? - Answers Precision astronomical data Suppose I were to spontaneously double the mass of the Earth: m(earth) -- 2m(earth) but everything else about the Earth's orbit remained the same (like its velocity, distance, and the mass of the Sun). Which of the following is true about the Earth's orbital energy? - Answers Earth's kinetic energy would be increased, but potential energy would be decreased In class on Rockets, we did some examples about different kinds of rockets, with different amounts of fuel and sizes. What is the best way to make your rocket go faster? - Answers Increase the fuel exhaust velocity Imagine that the Earth's orbital speed (the speed at which it orbits the Sun) doubled. What would happen to the Earth? - Answers It would escape the Sun's gravitational well and leave the Solar system How could you characterize the wavelength range of visible light? - Answers A few hundred nanometers What is physically different about visible light that enables us to see it, when we can't see other colors like infrared and ultraviolet? - Answers Our eyes have evolved chemicals that are sensitive to the wavelengths in visible light; they are not sensitive to infrared or ultraviolet. To see those, we would need different chemicals in our eyes than we have Which of the following statements is true? - Answers Light with a longer wavelength has lower frequency and less energy per photon Put the following types of light in order from longest wavelength (1) to shortest wavelength (8). - Answers 1. Radio waves 2. Microwaves 3. Infrared Light 4. Red Light 5. Green Light 6. Blue Light 7. Ultraviolet 8. X-ray What is true about the nature of light? - Answers Light is both a particle and a wave, this is known as particle-wave duality Match the photon energies given to the "colors" of light they correspond to: 2 eV - Answers Red Light Match the photon energies given to the "colors" of light they correspond to: 3 eV - Answers Blue Light Match the photon energies given to the "colors" of light they correspond to: 1 eV - Answers near infrared light, close to visible range Match the photon energies given to the "colors" of light they correspond to: .1 eV - Answers Far infrared, corresponding to the thermal radiation from things at room temperature Match the photon energies given to the "colors" of light they correspond to: 5 eV - Answers Ultraviolet Match the photon energies given to the "colors" of light they correspond to: 1000 eV - Answers X-ray Suppose we have a hypothetical element called onondagium. Its energy levels are: n = 1: 4 eV n = 2: 6 eV n = 3: 7.8 eV n = 4: 9.5 eV n = 5: 10 eV What photon energies correspond to the visible lines you would see in this spectrum? (Don't include any lines that you couldn't see with your eye.) If there aren't any visible lines, don't check any of the boxes. - Answers 1.8 eV, 2.2 eV, 2 eV, 1.7 eV If you placed a diffuse gas of the hypothetical element onondagium in a glass tube and run electric current through it (sort of like the discharge tubes we use in lab), what would the resulting spectrum look like? - Answers Bright lines on a dark background Below are the energy levels of a hypothetical element syracusium. • n = 1: 0 eV (ground state) • n = 2: 2.1 eV • n = 3: 3 eV • n = 4: 5 eV • n = 5: 9 eV Suppose syracusium is illuminated with 5 eV ultraviolet photons. Which visible photon energies would be produced? - Answers 2 eV, 2.1 eV, 2.9 eV and 3 eV Rattlesnakes, such as the diamondbacks common in Arizona and the timber rattlesnakes common in the Eastern United States, have special organs that can detect the thermal radiation given off by their prey. Their "picture" of the world looks much like the picture you saw using the thermal cameras in lab last week. This allows them to hunt their prey at night. Which of the following situations would allow an animal to hide from a rattlesnake? - Answers The animal is the same temperature as the rock it is standing on (for instance, it is a cold-blooded lizard whose temperature matches its surroundings) As you have seen, the Sun has very many dark lines in its absorption spectrum. There are some stars, however, that are missing many of the dark lines that the Sun has. What can you conclude about the other stars? - Answers Their atmospheres are missing some of the elements that the Sun has in its atmosphere. As you have seen, the Sun has a broad spectrum of continuous light emission that looks white to our eyes. Suppose you look out into space and see another star that appears red. What can you say about the temperature of that star? - Answers The surface temperature of the star is cooler than the Sun's surface temperature Suppose the fictional element unobtanium has energy levels as follows: n=1: 0 eV n=2: 2 eV n=3: 3.5 eV n=4: 5.1 eV Suppose that you shine photons with an energy of 2.5 eV on a gas of unobtanium at room temperature. What would happen? (Choose all possible answers.) - Answers They would pass through without anything happening. Recall from in class and in reading the Doppler shift for a wavelength of light: ((delta wavelength)/wavelength) = v/c Suppose you take a source of green light at 500 nm, and move it away from you at velocity v = 0.1 c. (aka 10% of the speed of light). At what wavelength and color will the green light source appear to you? - Answers 550 nm What is key fundamental physics that allows a refracting telescope to work? - Answers Light slows down and changes directions as it enters a material Before the introduction of space telescopes, how did astronomers reduce the impact of atmospheric distortion ("twinkling") on astronomical images? - Answers Locating telescopes on mountains Suppose you want to build a telescope. You want your telescope to have a magnification of 100. You have a large objective lens that has a diameter of 10 cm and a focal length of 200 cm. What should the focal length of your eyepiece be? - Answers 2 cm Recall Homework 7 Part 2, which a hot star with an intervening cloud of Hydrogen gas at location B ( This time, suppose instead of cooling the star, the star remains at it's original temperature of 5500 K, but the star and its cloud of Hydrogen gas starts moving at a velocity v = 0.5 c away from you. Do the Hydrogen absorption lines change wavelengths compared to the original (stationary) spectrum of the star? - Answers Yes, in this case the absorption lines get red-shifted compared to when the star was stationary. Why is the James Webb Space Telescope (JWST) able to see far infrared light (wavelengths around 10,000 nm) while the Hubble Space Telescope cannot? - Answers The JWST is at a lower temperature than the Hubble Space Telescope is What advantages are gained from making a telescope aperture larger? - Answers - It can see fainter objects that emit less light - It can see smaller structures and finer detail