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ASTRO 1 EXAM 2 NEWEST 2025 ACTUAL
EXAM COMPLETE 50 QUESTIONS AND
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- Relative to an observer at rest, time for an observer that travels at high speed: a. Is the same b. Is slower c. Is faster - CORRECT ANSWER ✔✔B
- The equivalence principle tells us that experiments performed on a spaceship accelerating through space at 1g will give the same results as experiments performed on Earth a. True b. False - CORRECT ANSWER ✔✔A
- If you could travel away from Earth at a speed close to the speed of light, you would find your own time to be running more slowly because of the time dilation. a. True b. False - CORRECT ANSWER ✔✔B
- Spacetime is a. The combination of time and the three dimensions of space b. A curved rubber sheet c. Another name for gravity - CORRECT ANSWER ✔✔A
- Which of the following regions of interstellar gas have the lowest densities and cannot form stars? a. Hot bubbles b. Molecular cloud cores c. Molecular clouds d. Warm atomic gas e. Cool atomic clouds - CORRECT ANSWER ✔✔A
- We know that a black hole lies at our galaxy's center because numerous stars near it have vanished over the past several years, telling us that they've been sucked in a. True b. False - CORRECT ANSWER ✔✔B
- True or False? If a black hole ten times more massive than our Sun were lurking just beyond Pluto's orbit, we'd have no way of knowing it was there a. True. Black holes do not emit light so they cannot be detected b. True. Such a low mass black hole would have no influence on the solar system
c. False. It would be readily apparent as a pulsating radio source in the outer solar system d. False. X-ray observations would reveal its presence as it sucked in material around it e. False. Such a black hole would measurably affect the orbits of the planets - CORRECT ANSWER ✔✔E
- You can see a clock in a spaceship moving past you at 90% of the speed of light. According to you, how much time would pass while the clock in the spaceship ticked through one minute? a. Less than one minute b. A minute on the ship, which is exactly two minutes for you c. A minute on the ship, which is the same as a minute for you d. More than one minute - CORRECT ANSWER ✔✔D
- Officer Albert departs the police station that orbits Earth. As the patrol ship accelerates to relativistic speeds, Officer Albert's thoughts turn to his twin brother, Stephen, who has never left Earth. They were born by Caesarean section at exactly the same time. Will they still be the same age when Albert returns from his patrol? a. No. Stephen will be older than Albert b. Yes, they will still be the same age c. No. Albert will be older than Stephen - CORRECT ANSWER ✔✔A
d. It's a paradox. One of them will be older than the other, but it's impossible to predict which one.
- Which of the following does NOT indicate the presence of a black hole: a. Gravitational deflection of light (gravitational lensing) b. Fast orbital motion of nearby stars c. Motion close to speed of light - mostly seen in jets coming from active galactic nuclei d. X-ray or Gamma ray emission - from ionized gas falling into the black hole (emitted from the accretion disk around the black hole) e. X-ray emission coming from the gas swirling down a vortex - CORRECT ANSWER ✔✔E
- Which of the following is not a property of a black hole that can be known? a. Angular momentum b. Charge c. Temperature d. Mass - CORRECT ANSWER ✔✔C
- If you are in a spacecraft accelerating at 9.8 m/s2 through interplanetary space, you will feel the same force you would feel if you were sitting still on the surface of the Earth. This is an expression of a. The fact that the speed of light is absolute, finite, and constant and is the fastest known speed
b. Einstein's equivalence principle c. A complete falsehood! Traveling through space is nothing at all like being on Earth d. The results of the Michelson-Morley experiment - CORRECT ANSWER ✔✔B
- The size (Schwarzschild radius) of a black hole depends on its a. Mass b. Composition c. Density d. All of the above e. A and C - CORRECT ANSWER ✔✔A
- Which of the following are not possible solutions to the Fermi Paradox? a. We are alone b. Life may be common in the Galaxy, but intelligent life may be exceedingly rare c. Other civilizations could be billions of years ahead of us and have no interest in us d. We are living in a simulated universe e. These are all "possible", though highly speculative, solutions - CORRECT ANSWER ✔✔E
- In what part of the spectrum are hot gas bubbles visible in the Milky Way? a. Gamma-rays b. Near-infrared c. Ultraviolet d. X-rays e. 21-centimeter emission (radio) - CORRECT ANSWER ✔✔D
- Which one of these objects would curve spacetime the LEAST, very near their surface? a. 1 Msun white dwarf with a radius of 6,000 km b. 2 Msun black hole with a radius of 6 km c. 3 Msun main sequence star with a radius of 2,000,000 km d. 2 Msun neutron star with a radius of 10 km e. 4 Msun red giant star with a radius of 100,000,000 km - CORRECT ANSWER ✔✔E
- Travel through a spacetime diagram is called a: a. Timeline b. Spaceline c. Worldline d. All of the above - CORRECT ANSWER ✔✔C
- Some light beams will follow curved paths
a. When measured inside a space ship that is coasting at high speed b. Under no circumstances c. When measured in the presence of an extreme gravitational field d. When measured from a reference frame that is not accelerating
- What are some pieces of evidence for the existence of supermassive black holes at the centers of galaxies? a. The fast orbital motions of stars and gas close to the center b. Energetic phenomena like jets and certain kinds of radio emission that arise form the behavior of matter around the supermassive black hole c. A and B d. None of the above - CORRECT ANSWER ✔✔C
- Which one of these objects would deflect the path of a photon of light from a very distant galaxy the LEAST, assuming the photon passes very near the surface (or event horizon) of each object. a. 3 Msun main sequence star with a radius of 2,000,000 km b. 1 Msun white dwarf with a radius of 6,000 km c. 2 Msun neutron star with a radius of 10 km d. 2 Msun black hole with a radius of 6 km e. 4 Msun red giant star with a radius of 100,000,000 km - CORRECT ANSWER ✔✔E
- Einstein showed that everything is relative a. True b. False - CORRECT ANSWER ✔✔B
- What happens to a photon as it is trying to escape the vicinity of a black hole? a. It turns into a Gamma-ray b. Its wavelength gets longer c. It slows down d. It will get sucked into the black hole - CORRECT ANSWER ✔✔B
- With a sufficiently powerful telescope, we could search for black holes by looking for funnel-shaped objects in space a. True b. False - CORRECT ANSWER ✔✔B
- Gravitational lensing occurs because a. Gravity curves space and light always follows the straightest possible path through space b. Gravity causes light to slow down c. The effects of gravity are indistinguishable from the effects of glass lenses - CORRECT ANSWER ✔✔A
- What produces the 21-centimeter emission line? a. Supernova remnants b. Super bubble emissions c. Atomic hydrogen gas d. CO in giant molecular clouds e. Planetary nebulae - CORRECT ANSWER ✔✔C
- What kind of diagram do physicists use to visualize complex concepts in Relativity? a. Spacetime diagram b. Minkowski diagram c. Penrose diagram d. A and B e. A, B and C - CORRECT ANSWER ✔✔D
- True of False? We can detect black holes with X-ray telescopes because matter falling into a black hole emits X-rays after it smashes into the event horizon. a. False, black holes do not have surfaces for material to smash into. The x-ray emission comes from gas as it falls toward the event horizon and heats up b. False, black holes are invisible and only apparent through their gravitational influence c. True, the energy of matter smashing into the event horizon is very high and creates strong x-ray emission
d. False, after matter smashes into the event horizon, its radiation cannot escape - CORRECT ANSWER ✔✔A
- Which of the following regions of interstellar gas have the lowest temperatures and can collapse to form stars? a. Cool atomic clouds b. Molecular cloud cores c. Hot bubbles d. Warm atomic gas - CORRECT ANSWER ✔✔B
- Of the following objects, on which one would time on its surface run most slowly? a. An object with the same mass as the Sun but twice as large in radius b. The Sun c. An object with the same mass as the Sun but only half as large in radius - CORRECT ANSWER ✔✔C
- Which of the following are not problems in trying to detect some manner of interstellar communication? a. Trying to pinpoint the right frequency to use b. Searching in the right direction at the right time c. The assumption that other civilizations would use radio or some other technology we would understand d. These are all problems - CORRECT ANSWER ✔✔D
- Which of the following must be true of a person who shares the same reference frame as you? a. The person must be sitting right next to you b. The person must be moving relative to you c. The person must be the same size as you - CORRECT ANSWER ✔✔B
- Which of the following is not a major idea of Einstein's general theory of relativity a. It is possible to travel through wormholes b. Time runs slower near strong gravitational fields c. Black holes can exist in spacetime, and falling into a black hole means leaving the observable universe d. Our universe can have no center or boundaries, yet be finite - CORRECT ANSWER ✔✔A
- What do we mean by gravitational time dilation? a. It is the idea that time runs slower in places where gravity is stronger b. It is the idea that everyone measures time differently, depending on his/her reference frame c. It is the idea that clocks run slow for people moving at high speed past you d. It is the idea that clocks run faster in stronger gravitational fields
- A person moving by you at high speed will measure time and space differently than you, but you will both agree that there is just a single reality in spacetime. a. True b. False - CORRECT ANSWER ✔✔A
- What evidence most convincingly suggests that there is a supermassive black hole at the center of our own Milky Way? a. The black hole causes gravitational lensing b. A relativistic jet is seen coming out of the core of the Milky Way c. The supermassive black hole is an X-ray binary star system d. Measurements of the velocities of stars at the center of the Milky Way indicate a large mass in a small space e. Hubble Space Telescope observations show gas swirling down a vortex - CORRECT ANSWER ✔✔D
- What is the mass of the object at the center of the Milky Way? a. 300 million solar masses b. 300,000 solar masses c. 40,000 solar masses d. 40 million solar masses e. 3 million solar masses - CORRECT ANSWER ✔✔E
- Einstein's general theory of relativity suggests that gravity is: a. Caused by curvature of spacetime b. F = G M1 M2/d (squared) c. One of four fundamental forces in nature - CORRECT ANSWER ✔✔A
- What would happen to Earth's orbit if our Sun suddenly became a black hole? a. Earth would gradually drift away from the black hole b. Earth would be flung into outer space c. Earth's orbit would not change d. Earth would be sucked into the center of the black hole - CORRECT ANSWER ✔✔C
- Which of the following is not relative in the special theory of relativity? a. Time b. Motion c. The speed of light - CORRECT ANSWER ✔✔C
- What does the general theory of relativity involve that the special theory does not? a. Electromagnetic interactions b. Eclipses
c. Gravity d. Quantum theory - CORRECT ANSWER ✔✔C
- If two events are simultaneous in one reference frame, are they also simultaneous in all reference frames? a. Yes, the speed of light is constant b. No, the events can happen at different times in another reference frame c. Yes, all frames experience events the same way in the same order d. No, the speed of light can change in different reference frames - CORRECT ANSWER ✔✔B
- The very bright radio source at Galactic Center shows lots of energy emitted from a small area of space. Its name is: a. Sagittarius A b. Scorpio X c. Sagittarius X - CORRECT ANSWER ✔✔A
- How do astronomers conclude that a compact object in an X- ray binary is a black hole, as opposed to something else (such as a neutron star)? a. The compact object shows gravitational lensing b. The compact object is black c. There is no sign of a pulsar or of pulsations
d. Its mass is larger than 3 solar masses and confirmed to a space smaller than a white dwarf - CORRECT ANSWER ✔✔D
- What type of radiation do astronomers use to study the emission of stars like our Sun? a. Microwave b. Radio c. Gamma rays d. Infrared e. Ultraviolet f. Optical g. X-rays - CORRECT ANSWER ✔✔F
- A black hole is: a. An object whose gravity is so strong that not even light can escape b. A mathematical object predicted by general relativity, which does not exist in reality c. A region of spacetime where space is falling faster than light d. A collapsed star e. A quasar - CORRECT ANSWER ✔✔A
- Where does one expect to find supermassive black holes? a. At the center of the Milky Way only
b. At the center of the Milky Way and other spiral galaxies c. At the center of the Milky Way, other spiral galaxies, and other non-spiral galaxies d. None of the above - CORRECT ANSWER ✔✔C
- Suppose that you get on a space ship and travel toward the star Sirius at 150,000 km/s at a speed of approximately half the speed of light. If you measure the speed of light arriving from Sirius, what figure will you obtain? a. 300,000 km/s b. It cannot be calculated c. 150,000 km/s d. 450,000 km/s - CORRECT ANSWER ✔✔A
- Gas is added to the interstellar medium by supernovae and planetary nebulae. What kind of gas would you expect that to be? a. Hydrogen gas b. Gas that has a mix of heavier elements in it, such as carbon, oxygen, silicon, iron, etc c. Helium gas d. There wouldn't be any gas - CORRECT ANSWER ✔✔B
- Suppose you see a friend moving by you at some constant speed. Your friend can equally well say that she is stationary and you are moving by her.
a. True b. False - CORRECT ANSWER ✔✔A
- The tidal force is the difference in the gravitational force between two parts of an object (between your head and your toes). The tidal force of a black hole will tear you apart: a. At the singularity b. Somewhere inside the event horizon c. At the event horizon d. Outside the event horizon if the black hole has a stellar-size mass, or inside the horizon if the black hole is supermassive - CORRECT ANSWER ✔✔D