Life Cycle of Low Mass Star

• What follows predictable stages in its life cycle?

  A star
• What does the route of a star's development depend on?

  Its initial mass
• What are the first four stages in the life cycle of stars?

  1. Nebula
  2. Protostar
  3. Main Sequence Star
  4. Red Giant

  
• What is a low mass star defined as?

  Less than about 8 times the Sun's mass
• What is the assumed mass of the Sun in the context of low mass stars?

  The Sun is assumed to be a low mass star
• What is the first stage in the life cycle of a star?

  Nebula

  
• What forms from a giant cloud of hydrogen gas and dust?

  A nebula
• What causes denser clumps of matter to form in a nebula?

  Gravitational attraction between individual atoms
• What is the term for the inward movement of matter in a nebula?

  Gravitational collapse
• What happens to the gas during the gravitational collapse?

  It heats up and glows
• What is formed as a result of gravitational collapse?

  A protostar
• How can protostars be detected?

  By telescopes observing infrared radiation
• What begins when the temperature of a protostar reaches millions of degrees Kelvin?

  The fusion of hydrogen nuclei to helium nuclei
• What continues to happen to a protostar as it attracts more gas and dust?

  Its temperature and pressure increase
• What increases the probability of fusion occurring in a protostar?

  More frequent collisions of particles
• What is the third stage in the life cycle of a star?

  Main Sequence Star
• What happens when a star reaches a stable state?

  Inward and outward forces are in equilibrium

  
• What begins when fusion reactions start in a star's core?

  The star joins the main sequence
• What produces radiation pressure in a main sequence star?

  Thermonuclear fusion of hydrogen nuclei

  
• How long do stars spend on the main sequence?

  Millions to billions of years
• What percentage of stars are main sequence stars?

  90%
• What is the mass range for main sequence stars?

  ~10% to 200 times the Sun's mass
• How long has the Sun been on the main sequence?

  4.6 billion years
• How long will the Sun remain on the main sequence?

  Estimated 6.5 billion years
• What happens to a low-mass star after the main sequence?

  It becomes a red giant
• What happens to hydrogen in the core of a low-mass star?

  It begins to run out
• What occurs when nuclear fusion slows in a low-mass star?

  The energy released by fusion decreases
• What happens to the core of a low-mass star when fusion slows?

  The star shrinks and compresses the core
• What happens to the outer layers of a low-mass star when fusion resumes?

  They expand and cool
• What is a red giant?

  A large, low-temperature, luminous star
• What nuclei are fused in a red giant?

  Helium nuclei into more massive nuclei
• What is the fifth stage in the life cycle of a low-mass star?

  Planetary Nebula
• What happens to the outer layers of a low-mass star during the planetary nebula stage?

  They are released
• What powers a white dwarf?

  Gravitational potential energy released during contraction
• What is the final stage in the evolution of a low-mass star?

  White dwarf
• What are the stages of evolution for low-mass stars after the main sequence?

  1. Red Giant
  2. Planetary Nebula
  3. White Dwarf

  
• What are the key points in the evolution of a low-mass star?

  • Hydrogen runs out
  • Core collapses
  • Outer layers expand and cool
  • Helium fuses into carbon and oxygen
  • Outer layers ejected as planetary nebula
  • Remnant core becomes a white dwarf
• What happens to the core of a low-mass star after it becomes a red giant?

  The core collapses and cannot fuse further
• What is the remnant of the core of a low-mass star called?

  White dwarf
• What is the temperature of a red giant compared to other stars?

  Low-temperature