Astrophysics

• How is gravitational field strength defined?

  As the gravitational force acting on a unit mass
• What are the key features of gravitational field lines around astronomical objects?


  • They indicate the direction of the gravitational force.
  • They show the strength of the gravitational field.
  • Patterns vary depending on the mass and distance of objects involved.
• What is the definition of gravitational potential at a point in space?

  It is the work done in moving a unit mass from infinity to that point
• How does the energy required to move mass between two points in a gravitational field depend on the path taken?


  It is independent of the path taken
• What is escape velocity?

  It is the minimum velocity required to escape a gravitational field to infinity
• What does special relativity deal with?

  Motion in inertial (non-accelerating) frames of reference
• What does general relativity deal with?

  Motion in non-inertial (accelerating) frames of reference
• What is the equivalence principle in general relativity?


  It states that it is not possible to distinguish between the effects of a uniform gravitational field and constant acceleration
• How is spacetime represented in general relativity?

  As three dimensions of space and one dimension of time
• What does general relativity interpret about mass and spacetime?

  Mass curves spacetime, and gravity arises from this curvature
• What is a geodesic in spacetime?

  It is the shortest distance between two points
• What are the characteristics of world lines in spacetime?

  • Represent the path of an object through spacetime.
  • Different shapes indicate different states of motion (stationary, constant velocity, accelerating).
• What is the escape velocity from the event horizon of a black hole?

  It is equal to the speed of light
• How does time appear to a distant observer at the event horizon of a black hole?

  Time appears to be frozen
• What is the Schwarzschild radius of a black hole?


  It is the distance from its center (singularity) to its event horizon
• How are stars formed in interstellar clouds?

  Gravitational forces overcome thermal pressure, causing a molecular cloud to contract
• What is the proton-proton chain in stellar fusion reactions?


  It converts hydrogen to helium
• What is the Hertzsprung-Russell (H-R) diagram used for?


  • Represents the classification of stars.
  • Shows the relationship between stellar luminosity and temperature.
  • Helps classify stars into categories like main sequence, giants, and white dwarfs.
• How can you determine stellar properties using the H-R diagram?

  By predicting the color of stars from their position in the diagram
• Where does hydrogen fusion occur in stars on the main sequence?


  In the core of the stars
• What happens when hydrogen fusion in the core of a star ceases?


  The core shrinks and becomes hot enough for helium fusion to begin
• What determines the lifetime of a star?

  The mass of the star
• What will every star ultimately become?

  A white dwarf, a neutron star, or a black hole