Chat with AIExam 11: Measuring the Stars: the Main Sequence and Its Meaning
Exam 1: Getting Started: Science, astronomy, and Being Human70 Questions
Exam 2: A Universe Made, a Universe Discovered71 Questions
Exam 3: A Universe of Universal Laws71 Questions
Exam 4: A Universe of Universal Laws70 Questions
Exam 5: The Architecture and Birth of Planetary Systems70 Questions
Exam 6: Home Base: Earth and Moon70 Questions
Exam 7: Sibling Worlds: Mercury, Venus, and Mars70 Questions
Exam 8: Gas, ice, and Stone: the Outer Planets70 Questions
Exam 9: Life and the Search for Habitable Worlds70 Questions
Exam 10: The Sun As a Star70 Questions
Exam 11: Measuring the Stars: the Main Sequence and Its Meaning70 Questions
Exam 12: Nursery of the Stars: the Interstellar Medium and Star Formation70 Questions
Exam 13: To the Graveyard of Stars: the End Points of Stellar Evolution70 Questions
Exam 14: Down the Rabbit Hole: Relativity and Black Holes70 Questions
Exam 15: Our City of Stars: the Milky Way70 Questions
Exam 16: A Universe of Galaxies69 Questions
Exam 17: The Cosmic Web: the Large-Scale Structure of the Universe70 Questions
Exam 18: Cosmology70 Questions
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All observed stars have roughly the same amount of hydrogen in their atmospheres.Why then are hydrogen lines less prominent in O stars than they are in A stars?
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(33) The figure below shows four stars on an HR diagram.Which star has the largest radius? 
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(42) 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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(36) Star A moves 1 arcsecond/year across the sky while star B moves 0.5 arcseconds/year.Star A has a parallax angle three times as large as star B.If neither star shows a Doppler effect,how do the space velocities of the two stars compare to each other?
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(32) Two stars orbit each other on circular orbits.The star with the larger orbital radius has a:
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(36) The Sun is expected to spend about 5 billion more years on the main sequence.If its luminosity increased suddenly to four times its usual value,how much time would it remain on the main sequence?
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(37) What property of Cepheid variable stars makes them useful for distance measures?
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(29) What property of a star's spectral lines allows astronomers to measure stellar masses?
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(34) What is the name for the force balance illustrated in the figure below?
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(44) What quantities must be measured in order to calculate the luminosity of a star?
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(33) How does the inclination of a spectroscopic binary star system's orbit affect astronomers' mass estimates of the stars?
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(40) How have astronomers learned about the life cycles of stars?
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(39) The figure below shows an HR diagram.What is the name for the feature marked "X"? 
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(28) The figure below shows a binary star system.Which of the following correctly characterizes the spectrum of this system at the instant shown in the figure? 
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