Topic 7 Astronomy

• What is the formula for weight in physics?

  $W =$$mg$
• What does weight (W) represent in physics?

  Weight is the force measured in Newtons (N) resulting from mass and gravitational acceleration.
• How does the value of gravitational acceleration (g) affect weight?

  The greater the value of g, the greater the weight of the object.
• What is the relationship between the mass of a planet and the value of g?

  The greater the mass of the planet, the greater the value of g on that planet.
• Why does more mass result in a stronger gravitational pull?

  More mass leads to a stronger gravitational pull, resulting in a higher value of gravitational acceleration (g).
• What are the main components of our Solar System?

  • The Sun (center of the Solar System)
  • Eight planets orbiting the Sun
  • Natural satellites orbiting the planets (e.g., the Moon)
  • Dwarf planets (e.g., Pluto, Ceres)
  • Asteroids and comets
• What is the mnemonic to remember the order of the planets in our Solar System?

  My Very Early Morning Jam Sandwich Usually Nauseates
• How do the sizes of planets differ in terms of composition?

  Smaller planets are primarily made of rock, while larger planets are primarily made of gas.
• What is the orbital plane of the planets in the Solar System?

  All planets orbit the Sun on the same plane.
• How do the rotation speeds of planets vary?

  All planets rotate, but at different speeds.
• What can cause a planet to rotate in the opposite direction?

  Past collisions can throw a planet's axis off balance, causing it to rotate in the opposite direction.
• Why do larger planets have rings?

  Larger planets have rings because their strong gravitational field attracts debris.
• What were the key features of the geocentric model of the Solar System?

  • Earth at the center
  • Planets, the Moon, and the Sun orbiting Earth
  • Orbits in perfect circles
  • Fixed background of stars
• What evidence supported the heliocentric model of the Solar System?

  • Mars' retrograde motion
  • Galileo's observation of moons orbiting Jupiter
  • Kepler's discovery of elliptical orbits
• What causes a planet to change direction while orbiting the Sun?

  The gravitational force causes the planet to change direction constantly while moving in a circle around the Sun.
• How does the speed of a planet change as it orbits the Sun?

  The speed of the planet remains constant, but its velocity is always changing due to direction changes.
• What happens to a planet's orbital speed if it moves closer to the Sun?

  If a planet moves closer to the Sun, its gravitational attraction increases, leading to an increase in orbital speed.
• What does red shift indicate about galaxies?

  Red shift indicates that galaxies are moving away from Earth.
• What does the emission spectrum show in relation to red shift?

  The emission spectrum shows black absorption lines shifted towards the red end, indicating red shift.
• How does red shift provide evidence for an expanding universe?

  The red shift increases with distance from Earth, supporting the idea of an expanding universe.
• How can the expansion of the universe be visualized using a balloon analogy?

  • Imagine the universe as an un-stretched balloon.
  • Galaxies are on the surface of the balloon.
  • As the balloon expands, the distance between galaxies increases.
  • Light from galaxies is red-shifted as they move away.
• What does the Cosmic Microwave Background (CMB) radiation indicate?

  CMB radiation indicates that the hot young universe has cooled and expanded over time.
• What does the red shift evidence suggest about the Big Bang theory?

  Red shift suggests that the universe is expanding and must have originated from a single point.
• What are the key points of the Steady State Theory?

  • Universe expands while matter is constantly created.
  • Maintains a constant density of matter.
  • Suggests the observable universe is the same at any time and place.
  • Evidence of evolving stars contradicts this theory.
• What is the life cycle of a star starting from a dust and gas cloud?

  Dust and gas clouds form nebulae, which collapse under gravity, increasing temperature and pressure until fusion occurs, forming a star.
• What happens when a star runs out of gas to fuse?

  The star collapses if it is massive, leading to a supernova, or it swells into a red giant and then contracts into a white dwarf if it is normal-sized.
• What are the stages of star formation and evolution?

  1. Dust and gas cloud forms nebulae.
  2. Gravitational attraction causes particles to clump together.
  3. Temperature and pressure increase, leading to fusion.
  4. Star forms and remains stable for billions of years.
  5. Star runs out of gas and evolves based on its mass.
• What wavelengths can be used to observe the universe?

  Observations can use any wavelength in the electromagnetic spectrum.
• Why do some telescopes need to be outside the atmosphere?

  Telescopes measuring X-rays, Gamma, and UV need to be outside the atmosphere because it does not allow these wavelengths to reach the ground.
• How have telescope technologies evolved over time?

  • Early refracting telescopes evolved into reflecting telescopes.
  • Reflecting telescopes can be made larger and cheaper.
  • Technological advances allow measurement of various parts of the EM spectrum.