Topic 7 - Astronomy

• The weight of a person may vary depending on the planet you are on, due to the gravitational field strength, and the mass of the person.
• What does our Solar system consist of?

  The Solar system consists of the Sun, planets, moons, asteroids, comets, and other celestial objects like artificial satellites.
• What are the 8 planets in our solar system?

  Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
• How did the ideas of the solar system change over time?


  Geocentric model: People thought that the Earth is at the center of the solar system and that the sun and moon as well as other planets orbit it.

  Heliocentric model: Astronomers like Galileo found out that stars never moved away from planets like Jupiter. Which led to the belief that the sun was at the center of the solar system.
• How do celestial bodies orbit?


  They orbit in a circular motion caused by the centripetal force acting towards the center of the circle. The force that makes this happen is gravity.
• The stronger the gravitational force of a celestial body, the larger the velocity is needed to balance with it.
• To have a stable orbit, The velocity must change if the radius of the orbit is closer or farther away. The closer the object, the faster its velocity.
• What is the steady state theory?

  The universe is eternal and has always existed. There is no beginning or end.
• What is the Big Bang theory?

  All the universe was in a dense small space that eventually exploded. This was 13.8 billion years ago. Due to the explosion, the universe is constantly expanding.
• What is the evidence found to support the big bang theory?

  Cosmic microwave background radiation, redshift of galaxies, and abundance of light elements.
• There is more evidence to support the big bang theory - therefore, it is more accepted than the steady state theory.
• What is red-shift?

  The shift of light towards longer wavelengths as it travels away from an observer, indicating that the object emitting the light is moving away. It has a similar concept to the Doppler effect.
• If the wavelength increases, this means that an object is moving away and it is emitting red light. If the wavelength decreases, it is coming closer and emitting blue light.
• How does redshift prove the Big Bang theory?

  It shows that galaxies are moving further away as they are emitting red light. This means that the universe is expanding - proving the big bang theory.
• redshift can prove both the Steady-State and the big bang theory.
• How does the discovery of Cosmic Background Radiation prove the Big Bang theory?

  It is thought that gamma radiation was released in the Big Bang. The expansion of the universe has stretched this radiation, resulting in the microwave radiation present today.
• What determines the type of lifecycle a star undergoes?

  The size of the star.
• What is the life cycle of a star?

  • Formation: Stars originate from nebulae, vast gas, and dust clouds.
  • Protostar: Protostars form through gravitational contraction and heat up during evolution.
  • Main Sequence: Stars sustain themselves through hydrogen fusion during this long-lasting phase.
  • Red Giant/Supergiant: Depletion of hydrogen leads stars to expand into red giants or supergiants.
  • End Stages: Low to medium-mass stars form white dwarfs; massive stars undergo supernova, resulting in neutron stars or black holes.
• Telescopes are used to observe the universe. There can be different types of telescopes such as X-ray telescopes (temp.) and radio telescopes (CMB). Telescopes are sent to space so that they have a clearer view of space as in the earth, there is a lot of light pollution.