Stars and planets

• What is the order of the planets in the solar system (starting from the Sun)?

  Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
• What type of planets are Mercury, Venus, Earth, and Mars?

  Terrestrial planets (rocky planets)
• What are the main characteristics of gas giants like Jupiter and Saturn?

  Large, low density, composed mostly of hydrogen and helium
• What is the difference between gas giants and ice giants?

  Gas giants (Jupiter, Saturn) are mostly hydrogen/helium; ice giants (Uranus, Neptune) contain more water, ammonia, and methane ices
• What is the Sun made of and what is its role in the solar system?

  Mostly hydrogen and helium; provides light and energy, and is the center of the solar system
• What are asteroids and where are most found?

  Rocky/metallic objects mostly found in the asteroid belt between Mars and Jupiter
• What are comets made of and where do they originate?

  Ice, dust, and rock; originate from the Kuiper Belt and Oort Cloud
• What are dwarf planets and name one example?

  Small spherical objects that orbit the Sun but haven't cleared their orbit; e.g., Pluto
• What units are used to measure distances in space?

  Kilometres, astronomical units (AU), and light years (l-y)
• What is 1 astronomical unit (AU)?

  The average distance from the Earth to the Sun (~150 million km)
• What is 1 light year?

  The distance light travels in one year (~9.46 trillion km)
• What are galaxies?

  Large collections of stars, dust, and gas bound by gravity (e.g., Milky Way)
• What are planetary systems?

  Systems of planets orbiting a star
• What is the first stage in a star's life cycle?

  Protostar
• What is a main sequence star?

  A star that fuses hydrogen into helium in its core
• What happens to a low-mass star after the main sequence?

  It becomes a red giant, then a white dwarf
• What happens to a high-mass star after the main sequence?

  It becomes a supergiant, then undergoes a supernova, and becomes a neutron star or black hole
• What causes a supernova?

  The collapse of a massive star after it stops fusion
• What is a white dwarf?

  The hot, dense core left behind after a red giant loses its outer layers
• What is a neutron star?

  An extremely dense core left after a supernova of a massive star
• What is a black hole?

  An object with gravity so strong that not even light can escape it
• What keeps a star stable during its life?

  Balance between gravitational force and pressure from gas and radiation
• How do stars generate energy?

  By nuclear fusion of hydrogen into helium and later heavier elements
• How are heavy elements formed and returned to space?

  Formed in giant stars and returned to space during supernova explosions
• What is the origin of the solar system?

  From the collapse of a gas and dust cloud (nebula), possibly triggered by a supernova
• What does the Hertzsprung-Russell (H-R) diagram show?

  It plots stars' luminosity against temperature and shows their life stages
• Where are main sequence stars found on the H-R diagram?

  In a diagonal band from top left (hot, bright) to bottom right (cool, dim)
• Where are white dwarfs found on the H-R diagram?

  Bottom left (hot but dim)
• Where are red giants and supergiants found on the H-R diagram?

  Top right (cool but bright)