Solar System — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
The Sun is the largest planet in our solar system and is made of solid iron.
Corrected: The Sun is a star at the center of our solar system and is made mostly of hydrogen and helium gas.
The Sun is a star, not a planet — it produces its own light and heat through nuclear fusion. It is made mostly of hydrogen and helium gas, not solid iron.
2. Fix the sentence:
Neil Armstrong was the first person to walk on Mars in 1969.
Corrected: Neil Armstrong was the first person to walk on the Moon in 1969.
Neil Armstrong walked on the Moon, not Mars, during the Apollo 11 mission on July 20, 1969. No human has ever walked on Mars.
3. Fix the sentence:
A telescope is a tool scientists use to listen to sounds coming from other planets.
Corrected: A telescope is a tool scientists use to observe distant objects in space by collecting light.
Telescopes collect and focus light to make distant objects appear closer and clearer. They are visual instruments, not audio devices — sound cannot travel through the vacuum of space.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. The Sun makes up about 99 percent of the total mass of the solar system.
The Sun is so enormous that it contains roughly 99 percent of all the mass in the solar system, with the planets, moons, and asteroids making up only about 1 percent.
2. Light from the Sun takes about 8 minutes to reach Earth.
Even though light travels at about 186,000 miles per second, the Sun is roughly 93 million miles away, so sunlight takes about 8 minutes to reach Earth.
3. The Hubble Space Telescope orbits Earth and takes detailed images of distant galaxies.
The Hubble Space Telescope orbits about 340 miles above Earth, avoiding atmospheric distortion so it can capture extremely sharp images of distant galaxies and nebulae.
4. The International Space Station is a laboratory where astronauts live and work in orbit.
The International Space Station (ISS) orbits Earth roughly every 90 minutes, serving as a laboratory where astronauts from many countries conduct science experiments in microgravity.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Why is the Sun important to life on Earth?
Sample answer: The Sun provides the light and heat energy that Earth needs. Plants use sunlight to make food through photosynthesis, and the Sun's warmth keeps temperatures suitable for living things.
The Sun drives nearly all life on Earth. Plants use its light for photosynthesis to produce food, and its heat keeps our planet warm enough for liquid water, which is essential for living things.
2. Name one spacecraft or mission that explored the outer solar system and describe what it studied.
Sample answer: The Voyager missions traveled past Jupiter, Saturn, Uranus, and Neptune, sending back detailed photographs and data about each planet's atmosphere, rings, and moons.
The Voyager 1 and 2 missions launched in 1977 and flew past all four outer planets, sending back the first close-up photographs of Jupiter's storms, Saturn's rings, Uranus's tilted axis, and Neptune's winds.