8.1.2 Life Cycle of a Star

• The formation of a star begins with a nebula
• Steps in the formation of a star from a nebula

  1️⃣ Nebula undergoes gravitational collapse

  2️⃣ A protostar forms at the center

  3️⃣ Temperature and pressure in the core increase

  4️⃣ Nuclear fusion initiates

  5️⃣ A new star is born
• During the Main Sequence Stage, a star converts hydrogen into helium
• Match the stage with its characteristics:

  Main Sequence ↔️ Hydrogen to Helium, Stable, Yes

  Pre-Main Sequence ↔️ None, Increasing, No

  Post-Main Sequence ↔️ Heavier elements, Unstable, No
• When a star exhausts its hydrogen fuel in the core, it enters the Red Giant
• The surface temperature of a Red Giant is lower than that of a Main Sequence star.

  True
• The process that powers a star is called nuclear fusion
• A Red Giant is significantly larger than a star in the Main Sequence Stage.


  True
• How does the luminosity of a Red Giant compare to a star in the Main Sequence Stage?

  Higher
• A Red Giant forms when a star exhausts its hydrogen fuel in the core during the Main Sequence Stage.


  True
• What does the core of a Red Giant eventually initiate fusion into?

  Carbon
• Helium fusion in a Red Giant produces carbon, while hydrogen fusion in the Main Sequence Stage produces helium.


  True
• After the Main Sequence Stage, a star undergoes significant changes in its structure and energy generation.
• Steps in the formation of a star

  1️⃣ Nebula

  2️⃣ Gravitational Collapse

  3️⃣ Protostar

  4️⃣ Nuclear Fusion
• The Main Sequence Stage is the longest and most stable period in a star's life cycle.


  True
• What stage does a star enter after it exhausts its hydrogen fuel in the core during the Main Sequence Stage?

  Red Giant Phase
• In the Red Giant Phase, the star's surface temperature decreases, giving it a red color.
• What heavier element is formed during helium fusion in the Red Giant Phase?

  Carbon
• Match the stage with the type of nuclear fusion occurring:

  Main Sequence ↔️ Hydrogen to Helium

  Red Giant ↔️ Helium to Carbon
• Order the steps in the formation of a Planetary Nebula:

  1️⃣ Red Giant Phase

  2️⃣ Pulsations

  3️⃣ Stellar Winds

  4️⃣ Ionization
• What remains at the center of a Planetary Nebula?

  White Dwarf
• White Dwarfs produce energy through nuclear fusion.

  False
• After a supernova, the star's core collapses to form either a neutron star or a black hole.
• What is a neutron star composed almost entirely of?

  Neutrons
• Black holes have infinite density at their core.

  True
• What is a nebula composed mainly of?

  Hydrogen and helium
• What is the longest and most stable phase of a star's life cycle?

  Main Sequence Stage
• The Main Sequence Stage can last for billions of years.


  True
• Match the stage of a star's life with its characteristic:

  Main Sequence ↔️ Hydrogen to Helium fusion ||| Stable hydrostatic equilibrium

  Red Giant ↔️ Helium to Carbon fusion ||| Lower surface temperature
• In the Red Giant Phase, helium fuses into carbon
• What type of remnant is left behind after a star ejects its outer layers as a planetary nebula?

  White Dwarf
• What is the central star of a Planetary Nebula called?

  White Dwarf
• Steps in the formation of a Planetary Nebula

  1️⃣ Red Giant Phase

  2️⃣ Pulsations

  3️⃣ Stellar Winds

  4️⃣ Ionization
• A Planetary Nebula has ongoing nuclear fusion in its core

  False
• Match the stellar characteristic with the correct stage in a star's life cycle:

  Nuclear Fusion of Hydrogen to Helium ↔️ Main Sequence

  Extremely High Density ↔️ White Dwarf

  Significantly Larger Size ↔️ Red Giant
• Steps in the formation of a Supernova

  1️⃣ Massive Star Life Cycle

  2️⃣ Nuclear Fusion

  3️⃣ Red Supergiant Phase

  4️⃣ Core Collapse

  5️⃣ Supernova Explosion

  6️⃣ Remnant
• Supernovae are essential for distributing heavy elements
• What is the process called where a nebula contracts under its own gravity?

  Gravitational collapse
• The Main Sequence Stage is the longest and most stable stage of a star's life cycle.

  True
• What is the term for the balance between outward pressure and inward gravity in a star?

  Hydrostatic equilibrium