Astronomy Unit 7 Exam - Questions & Answers Accretion is a gradual growth of a body by the accumulation of other, smaller bodies. White dwarf is a star
... [Show More] with sufficiently high surface temperature that it glows white. Chandrasekhar limit is the maximum possible mass of a white dwarf. Process of Science: Stars Leaving the Main Sequence Part A: A star is in hydrostatic equilibrium when the outward push of pressure due to core burning is exactly in balance with the inward pull of gravity. When the hydrogen in a star's core has been used up, burning ceases, and gravity and pressure are no longer in balance. This causes the star to undergo significant changes. Which of the following evolutionary changes would bring a star back into hydrostatic equilibrium? -A small increase in the star's internal pressure and temperature causes the star's outer layers to expand and cool. -A small decrease in the star's internal pressure and temperature causes the star's outer layers to contract and heat up. Process of Science: Stars Leaving the Main Sequence Part B: When a star's core hydrogen has been fully depleted via hydrogen burning, the star becomes unstable. The internal structure of the star changes as a result of the new instabilities within its interior. Which of the diagrams below shows the internal structure of a star immediately after running out of its core hydrogen? C: burning hydrogen shell, nonburning hydrogen envelope, and nonburning helium core. Process of Science: Stars Leaving the Main Sequence Part C: As you learned in Part B, a nonburning helium core surrounded by a shell of hydrogen-burning gas characterizes the subgiant stage of stellar evolution. As time goes on, the star continues to evolve, and eventually, it becomes a red giant. Rank the stages a star goes through as it evolves from a subgiant into a red giant, from latest to earliest. -The star becomes a red giant. -The surface of the star becomes brighter and cooler. -Pressure from the star's hydrogen-burning shell causes the nonburning envelope to expand. -The shell of hydrogen surrounding the star's nonburning helium core ignites. -The star's nonburning helium core starts to contract and heat up. -Pressure in the star's core decreases. Process of Science: Stars Leaving the Main Sequence [Show Less]