Astrophysics Fundamentals Quiz

Grade 12 · Science · Quiz

Challenge your understanding of stellar evolution, cosmology, and the physical laws governing the universe.

Questions

1. Which law states that the square of a planet's orbital period is proportional to the cube of its semi-major axis?

   1. Newton's law of gravitation
   2. Kepler's First Law
   3. Kepler's Third Law
   4. Hubble's Law
   Show answer

   Answer: Kepler's Third Law

   Kepler's Third Law states T² ∝ a³; this relationship arises from combining Newtonian gravity with circular orbital mechanics and holds for all orbiting bodies.

2. What evidence most directly supports the concept that the universe is expanding?

   1. The existence of black holes
   2. The redshift of distant galaxy spectra
   3. The detection of gravitational waves
   4. The presence of dark matter halos
   Show answer

   Answer: The redshift of distant galaxy spectra

   Distant galaxies show spectral lines shifted toward red, indicating recession; the degree of redshift scales with distance (Hubble's Law), confirming universal expansion.

3. What is the approximate composition (by energy density) of the universe according to the Lambda-CDM model?

   1. 70% dark energy, 25% dark matter, 5% ordinary matter
   2. 50% dark matter, 50% ordinary matter
   3. 90% ordinary matter, 10% dark energy
   4. 60% dark energy, 40% dark matter
   Show answer

   Answer: 70% dark energy, 25% dark matter, 5% ordinary matter

   The Lambda-CDM model, supported by CMB data and supernova surveys, indicates ~68% dark energy, ~27% dark matter, and ~5% baryonic (ordinary) matter.

4. A star with 20 solar masses will most likely end its life as a:

   1. White dwarf
   2. Planetary nebula
   3. Neutron star or black hole
   4. Red dwarf
   Show answer

   Answer: Neutron star or black hole

   Stars >8 solar masses undergo core-collapse supernovae; the remnant is a neutron star if the core mass is ~1.4-3 M☉, or a black hole if above that threshold.

5. The Stefan-Boltzmann law relates a star's luminosity to which property?

   1. Mass and radius only
   2. Surface temperature (to the fourth power) and surface area
   3. Rate of nuclear fusion reactions
   4. Distance from the center of its galaxy
   Show answer

   Answer: Surface temperature (to the fourth power) and surface area

   The Stefan-Boltzmann law: L = 4πR²σT⁴; luminosity scales with surface area (4πR²) and the fourth power of surface temperature (T⁴).

6. Which type of galaxy is characterized by older, reddish stars, no spiral arms, and little active star formation?

   1. Spiral galaxy
   2. Irregular galaxy
   3. Elliptical galaxy
   4. Barred spiral galaxy
   Show answer

   Answer: Elliptical galaxy

   Elliptical galaxies contain predominantly old, metal-poor red stars, lack significant interstellar gas/dust, and show little ongoing star formation.

7. The observable universe is larger than the entire universe.

   Show answer

   Answer: False

   The observable universe is the portion we can see (light-travel distance since the Big Bang); the entire universe may be vastly larger or infinite.

8. The distance that light travels in one year, approximately 9.46 × 10^15 meters, is called a _____.

   Show answer

   Answer: light-year

   A light-year is the distance light travels in one Julian year at c ≈ 3×10⁸ m/s; it is used to express astronomical distances on stellar and galactic scales.

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