8.1.2 Life Cycle of a Star

• What type of material is ejected into space during the formation of a planetary nebula?

  Gas and dust
• A white dwarf is a hot, dense core of a star that is no longer capable of nuclear fusion.
• After the red giant phase, low-mass stars proceed through the planetary nebula and white dwarf stages
• What creates a planetary nebula?

  Ejection of outer layers
• A white dwarf is capable of nuclear fusion.

  False
• Stages of the red supergiant phase for high-mass stars

  1️⃣ Exhaustion of hydrogen fuel

  2️⃣ Core contraction

  3️⃣ Fusion of helium, carbon, and oxygen

  4️⃣ Increase in luminosity
• How does the lifespan of a red supergiant compare to a red giant?

  Much shorter
• A star is a massive, luminous ball of gas held together by its own gravity
• A red supergiant may end its life as a neutron star or a black hole.
• A supernova occurs when the core of a massive star collapses under its own gravity
• What is the outcome of a supernova explosion?

  Neutron star or black hole
• The Orion Nebula is a region where stars are actively forming.
• What is the primary fusion process in the main sequence stage?

  Hydrogen into helium
• The Sun is a star and the center of our solar system.
• During the main sequence, a star maintains equilibrium between gravity and outward pressure
• What is a nebula composed of?

  Hydrogen and helium
• Stages of the red giant phase for low-mass stars

  1️⃣ Exhaustion of hydrogen fuel in the core

  2️⃣ Core contraction and heating

  3️⃣ Hydrogen fusion in a shell

  4️⃣ Expansion and cooling of the star
• Gravity causes a nebula to collapse, forming a protostar
• What are the two final stages for low-mass stars after the red giant phase?

  Planetary nebula, white dwarf
• The Orion Nebula is an example of a region where stars are actively forming.
• A planetary nebula is formed when the outer layers of the red giant are ejected into space
• What is the primary fusion process in a main sequence star?

  Hydrogen to helium
• The material ejected during the formation of a planetary nebula is enriched with elements like carbon and nitrogen.
• During the main sequence, a star is in equilibrium
• What is the final state of a low-mass star after the planetary nebula disperses?

  White dwarf
• The outward pressure from fusion in a main sequence star balances the inward force of gravity.
• A white dwarf is a small, hot, and dense remnant core of a star no longer capable of nuclear fusion
• What primary fusion process occurs in the core of a main sequence star?

  Hydrogen to helium
• In a main sequence star, the outward pressure from fusion is balanced by the inward force of gravity
• Main sequence stars are in a stable equilibrium due to hydrostatic and thermal balance.
• What is released during the fusion of hydrogen into helium in a main sequence star?

  Energy
• Match the feature with the correct description for main sequence stars:

  Primary Fusion Process ↔️ Hydrogen to helium

  Equilibrium ↔️ Hydrostatic and thermal

  Stability ↔️ Long-lasting
• How long will our Sun remain in the main sequence phase?

  About 10 billion years
• The luminosity of a main sequence star varies depending on its mass
• Our Sun is a main sequence star that will remain in this phase for about 10 billion years.
• What is the primary difference between low-mass and high-mass stars in terms of their main sequence duration?

  Low-mass stars last longer
• Low-mass stars evolve into a red giant before becoming a planetary nebula and then a white dwarf
• Our Sun is a low-mass star that will eventually become a white dwarf.
• What type of fusion occurs in the core of a low-mass star during the red giant phase?

  Hydrogen shell fusion
• Compared to the main sequence, a red giant is significantly larger