Questions and Answers
What powers a star?
fusion
In which of the following ways are earthquakes and oscillations on the Sun similar?
They propagate through the entirety of the objects.
A fusion reaction between nuclei A and B releases energy if the resulting nucleus:
is less massive than the total mass of A and B.
What is required to overcome the electrical repulsion of atomic nuclei?
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The Sun produces energy through:
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What has provided the best data about the interior of the Sun?
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What is the fate of positrons produced through fusion in the Sun's core?
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Why does fusion take place at very high temperatures?
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The most direct measurement of the fusion reactions within the Sun comes from:
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Solar neutrinos: (Select all that apply)
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What is the net result of the proton-proton chain in the Sun?
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When energy is carried by photons, astronomers call it:
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Which of the following energy transport mechanisms does NOT occur to a significant degree in the Sun? (Select all that apply)
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Convection in the Sun can be observed through:
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Approximately what fraction of the Solar System's mass is inside the Sun?
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Sunspots are areas of:
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What forces maintain hydrostatic equilibrium in an object?
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Which of the following is necessary for the solar dynamo to operate? (Select all that apply)
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Which of the following events have caused extensive power outages on Earth?
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Which of the following is NOT related to the solar magnetic cycle? (Select all that apply)
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A sunspot has a temperature 80% as large as the rest of the Sun's surface. How much LESS light does it produce per unit area than the rest of the Sun?
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Where does fusion occur in the Sun?
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How are oscillations of the Sun's surface measured?
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Arrange the following layers of the Sun in order from most to least dense:
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Which of the following properties decreases from the Sun's core to its outermost layer?
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How have astronomers learned about the life cycles of stars?
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Two stars orbit each other on circular orbits. The star with the larger orbital radius has a:
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Which of the following must be measured in order to determine a star's proper motion?
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Stars A and B have equal brightness, but star B is eight times as far from Earth as star A. How much more luminous is star A than star B?
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What properties of Cepheid variable stars are most often measured to determine their distance?
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What was Henrietta Leavitt's most important contribution to astronomy?
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Star A's spectrum is most intense at 500 nm, while star B's spectrum is most intense at 750 nm. If star A has a temperature of 5,800 K, what is the temperature of star B?
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Which of the following combinations of measurements CANNOT be used to determine a star's radius? (Select all that apply)
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Star A has an apparent magnitude of 7, while star B has an apparent magnitude of 12. If star A is four times more luminous than star B, how do the distances of the two stars compare?
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Star A is twice as luminous as star B but has half the temperature of star B. How large is the radius of star A compared to star B?
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Star A is four times as luminous as star B. Star B's spectrum peaks at 300 nm, while star A's spectrum peaks at 150 nm. How large is the radius of star A compared to star B?
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Which of the following correctly orders the spectral types of stars from coolest to hottest? (Select all that apply)
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Which of the following is necessary to construct a modern model of a star? (Select all that apply)
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What quantities must be measured in order to calculate the luminosity of a star?
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What determines the location of a star on the main sequence?
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Massive stars:
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Which of the following stellar spectral types shows the most molecular absorption lines?
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A stellar model:
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On the main sequence, a star's spectral type is ultimately determined by its:
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If star A has an apparent magnitude of 8 while star B has an apparent magnitude of 13, then star A is ________ than star B.
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Which of the following quantities is NOT necessary to observe in order to construct an HR diagram of a system of stars?
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Which of the following inputs are necessary for astronomers to compute the stellar evolutionary track of a star?
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A star has a parallax of 0.05 arcseconds. How far away from Earth is the star?
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What property of a star can best be used to determine its temperature?
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What property of a star's spectral lines allows astronomers to measure stellar masses?
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Which of the following is a key constituent of the interstellar medium? (Select all that apply)
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Which of the following lists the phases of the interstellar medium in order, from densest to least dense:
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Giant molecular clouds are typically:
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Which of the following adjectives best describes the interstellar medium?
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Which of the following helps support molecular clouds against gravitational collapse? (Select all that apply)
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A T Tauri star is a:
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A massive protostar is more luminous than a low-mass protostar because it:
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A protostar becomes a star when:
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A brown dwarf is a:
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A star with which of the following masses is most likely to form in a molecular cloud?
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What is the net result of the CNO cycle?
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An isolated star's eventual fate is ultimately determined by its:
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As a star moves along the red giant branch, how does it move on the HR diagram?
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What causes a planetary nebula?
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What supports a white dwarf star against gravity?
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Which of the following describes the evolutionary stages of a star with three times the mass of the Sun? (Select all that apply)
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How does a horizontal branch star produce energy?
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Why does a red giant grow in radius?
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The Sun will end its life as a:
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What is the source of most of the carbon and oxygen in the interstellar medium?
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A white dwarf has a temperature 10 times that of the Sun, but it has a radius 1,000 times smaller than the Sun. What is its luminosity?
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Why does a red giant fuse hydrogen more rapidly than a main sequence star of the same mass?
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What happens when a massive star's core becomes iron?
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What carries the bulk of the energy from the gravitational collapse of a massive star's core during a supernova?
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Why does stellar fusion end with an iron core?
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Which of the following is closest in radius to a neutron star?
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What kind of remnant will a 100 MSun star leave?
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An astronomer observes two Type Ia supernovas in different galaxies. The first is in a galaxy 100 Mpc away. If the second supernova is 106 times fainter than the first but has an identical light curve, how far away is the second supernova's host galaxy?
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Why are pulsars periodic?
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The period between pulses from a particular pulsar increases slowly with time. This implies that the:
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Two stars orbit each other as a close binary system. When the system forms, star A has 10 solar masses and star B has 3 solar masses. Which of the following is most likely to happen in the future?
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Which of the following did Einstein determine to be a constant of nature?
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Einstein showed that Newton's physics is:
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The general theory of relativity includes an explanation of:
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What are black holes?
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The first experimental verification of the general theory of relativity was:
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According to the general theory of relativity, gravity: (Select all that apply)
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According to the general theory of relativity, a satellite orbits Earth because:
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Which of the following effects must be accounted for to make accurate measurements with global positioning system satellites? (Select all that apply)
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A galaxy is positioned precisely behind another, very massive galaxy on the sky. We would observe the more distant galaxy as a:
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What kind of stars are most likely to form black holes?
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Why is the Schwarzschild radius significant?
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What do astronomers believe exists in the center of nearly every galaxy?
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The first evidence for supermassive black holes at the centers of galaxies came from:
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An accretion disk around a black hole is threaded by magnetic fields. What is a likely result of this configuration?
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What is the observational evidence that black hole jets are launched very close to the event horizon?
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What stops the collapse of the most massive stars at the end of their lives?
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A set of stars all initially have the same mass of 20 MSun, but their other properties differ. Which is LEAST likely to form a black hole at the end of its life?
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Study Notes
Stellar Fusion and Energy Production
- Fusion reactions in stars, like the Sun, are powered by nuclear fusion, particularly via the proton-proton chain.
- Energy from fusion is released when the resultant nucleus is less massive than the initial nuclei.
- High temperatures are essential for fusion as they enable protons to overcome their mutual electrical repulsion through high velocities.
- Fusion occurs in the Sun's core, producing helium-4 nuclei, neutrinos, positrons, and gamma rays.
Neutrinos and Helioseismology
- Helioseismology provides insights into the Sun's interior, revealing data about its structure.
- Neutrinos, emitted during fusion, are crucial for studying the fusion process, allowing for direct measurement of reactions.
- Solar neutrinos have had detection issues until 2002, serving as valuable probes of the proton-proton chain and changing identities en route to Earth.
Energy Transfer Mechanisms in the Sun
- Energy transport in the Sun principally occurs through radiative transport and convection; conduction is negligible.
- Granulation on the Sun’s surface is observable evidence of convective processes.
Solar Structure and Dynamics
- Approximately 99.9% of the Solar System's mass resides in the Sun, located within various layers including the core, radiative zone, and convective zone.
- Hydrostatic equilibrium in stars is maintained by the balance of pressure and gravity, with rapid and differential rotation essential for solar dynamo operation.
Solar Phenomena
- Sunspots are associated with intense magnetic fields and have lower temperatures compared to the Sun's surface, resulting in less light output.
- Coronal mass ejections can lead to extensive power outages on Earth, affecting communication systems.
Stellar Lifecycles and Classification
- The life cycle of stars is determined by their mass; massive stars have shorter lifetimes due to fast fuel consumption.
- The Hertzsprung-Russell (HR) diagram is used to characterize star properties, which include brightness and color.
- Stellar spectral types are classified from coolest to hottest as MKGFABO.
Star Measurement Techniques
- To determine a star’s proper motion, angular position must be measured over time.
- Luminosity calculations require brightness and distance, while temperature is most effectively assessed via color.
Black Holes and Stellar Remnants
- The fate of stars crucially depends on their initial mass, with those exceeding about 30 solar masses likely forming black holes.
- A black hole’s Schwarzschild radius marks the event horizon, beyond which nothing can escape.
- Supernovae and pulsar observations provide crucial data on stellar evolution and black hole formation.
Theoretical Foundations in Astronomy
- Einstein's theories revolutionized understanding of gravity, describing it as warped space-time and establishing the speed of light as a universal constant.
- General relativity accounts for light travel times and the relative effects of gravity, both significant for precise astronomical measurements, such as those used in GPS.
Interstellar Medium and Protostars
- The interstellar medium consists of gas and dust with varying densities spanning molecular clouds to coronal gas.
- A protostar becomes a star when nuclear fusion starts, with all stars forming from molecular clouds.
Additional Stellar Insights
- The ongoing study of Cepheid variable stars has revealed insights into distance measurement in astronomy.
- The evolution of stars like T Tauri and red giants involves phases that shape their eventual transformation into remnants like white dwarfs or supernovae.
Studying That Suits You
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Description
Test your knowledge of astronomy with these flashcards. This quiz covers topics such as stellar fusion, seismic activities related to the Sun, and details about nuclear reactions. Perfect for students needing a quick review or anyone interested in the wonders of the universe.