Our Solar System

The solar system is the collection of planets and other celestial objects that orbit around the Sun. The Sun, which is the center of the solar system, contains 99.86% of the total mass of the solar system. The rest of the mass is shared among the eight planets and other objects like asteroids, comets, and dwarf planets.

The eight planets of our solar system, in order from the sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The four inner planets, Mercury, Venus, Earth, and Mars, are called the terrestrial planets because they are primarily made of rock and metal. The outer planets, Jupiter, Saturn, Uranus, and Neptune, are called the gas giants because they are made mostly of gas and ice.

The solar system also includes dwarf planets such as Pluto, which was once considered a planet, and Ceres, which is the largest object in the asteroid belt between Mars and Jupiter. There are also several other smaller objects in the solar system, including comets and asteroids.

The solar system is about 4.6 billion years old, and it is believed to have formed from a giant cloud of gas and dust called the solar nebula. As the cloud collapsed, it formed a spinning disk with the Sun at the center. The planets and other objects formed from this disk as gravity pulled the material together.

The solar system is constantly changing, with planets and other objects moving and interacting with each other. Many missions have been sent to explore the solar system, including NASA’s Voyager missions, which have explored the outer planets and are now traveling beyond the edge of the solar system.

Scroll down for more facts and trivia about our solar system or click ‘Start Quiz’ to start our interactive quiz on ‘Our Solar System’

The planets of our solar system

Mercury

• Mercury is the smallest planet in the solar system.
• It has a very thin atmosphere and no moons.
• Mercury is the closest planet to the Sun, and as a result, it has a very short year (88 Earth days).
• The planet’s surface is covered in craters, cliffs, and flat plains.
• It has the highest temperature variation of any planet in the solar system, with temperatures ranging from -173°C to 427°C.
• Mercury has been visited by only one spacecraft, NASA’s Mariner 10, which flew by the planet three times in the 1970s.
• Its core makes up about 85% of the planet’s total volume.
• Mercury is named after the Roman messenger god.
• Its day (rotation) is longer than its year (orbit).
• It is the second densest planet in the solar system after Earth.

Venus

• Venus is the second planet from the Sun and is often referred to as Earth’s twin because of its similar size and composition.
• It has a thick atmosphere made primarily of carbon dioxide and sulfuric acid.
• Venus is the hottest planet in the solar system with surface temperatures that can reach 462°C.
• Its day (rotation) is longer than its year (orbit).
• Venus rotates in the opposite direction of most planets, including Earth.
• It has no moons.
• Venus has been visited by numerous spacecraft, including NASA’s Magellan and the Soviet Union’s Venera series.
• Its surface is covered in volcanoes, craters, and vast plains.
• Venus is named after the Roman goddess of love and beauty.
• Its atmosphere is so thick that it reflects a significant amount of the Sun’s light, making it the brightest object in the sky after the Sun and Moon.

Earth

• Earth is the only planet in the solar system known to support life.
• It has one moon, which is the fifth-largest moon in the solar system.
• Earth’s atmosphere is made up of 78% nitrogen, 21% oxygen, and 1% other gases.
• It is the only planet in the solar system with liquid water on its surface.
• Earth’s magnetic field protects the planet from harmful solar radiation.
• The planet has an active tectonic system with shifting plates that cause earthquakes and volcanic eruptions.
• Earth’s atmosphere is responsible for protecting the planet from meteors, which burn up in the atmosphere before reaching the surface.
• Earth’s rotation is slowing down over time.
• The highest point on Earth is Mount Everest, which stands at 8,848 meters (29,029 feet) tall.
• The lowest point on Earth is the Challenger Deep, which is the deepest known point in the ocean at 10,924 meters (35,840 feet).

Mars

• Mars is often referred to as the Red Planet because of its reddish appearance.
• It has a thin atmosphere made primarily of carbon dioxide.
• Mars has two small moons, Phobos and Deimos.
• The planet has the largest volcano in the solar system, Olympus Mons, which stands at 22 kilometers (13.6 miles) tall.
• Mars has the largest canyon in the solar system, Valles Marineris, which is 4,000 kilometers (2,500 miles) long and up to 7 kilometers (4.3 miles) deep.
• It has polar ice caps made of water and carbon dioxide.
• Mars has been visited by numerous spacecraft, including NASA’s Curiosity and Perseverance rovers.
• The planet’s day is slightly longer than Earth’s, at 24 hours and 39 minutes.
• Mars is named after the Roman god of war.
• It has a history of flowing water on its surface, which has led to speculation about the possibility of life on the planet.
• Mars is one of the planets that is being targeted for future manned missions by NASA and other space agencies.

Jupiter

• Jupiter is the largest planet in the solar system.
• It has a very strong magnetic field that traps radiation, making it the most radioactive planet in the solar system.
• Jupiter has a very thin ring system and over 70 moons.
• Its Great Red Spot is a giant storm that has been raging for at least 350 years.
• Jupiter’s atmosphere is made primarily of hydrogen and helium.
• It has the shortest day of any planet in the solar system, at just under 10 hours.
• Jupiter’s moon Europa is believed to have a subsurface ocean, making it a potential candidate for the search for extraterrestrial life.
• It is named after the king of the Roman gods.
• Jupiter has been visited by several spacecraft, including NASA’s Juno mission, which is currently orbiting the planet.
• It played a critical role in shaping the solar system, as its massive gravity influenced the formation and positioning of the other planets.

Saturn

• Saturn is the second-largest planet in the solar system and is known for its beautiful ring system.
• It has over 80 moons, including the largest moon in the solar system, Titan.
• The rings of Saturn are made primarily of ice particles and rock fragments.
• Its largest moon, Titan, has a thick atmosphere and is the only moon in the solar system with a substantial atmosphere.
• Saturn’s day is just over 10 hours long.
• It has a magnetic field that is weaker than Jupiter’s but still strong enough to create auroras.
• Saturn’s atmosphere is made primarily of hydrogen and helium.
• The Cassini spacecraft, which was a joint NASA-ESA mission, spent over a decade orbiting Saturn and studying its rings, moons, and atmosphere.
• It is named after the Roman god of agriculture.
• Saturn has been observed for thousands of years, and its rings were first discovered by Galileo in 1610.

Uranus

• Uranus is the third-largest planet in the solar system and is known for its unusual orientation – its axis of rotation is tilted at an angle of 98 degrees relative to the plane of its orbit around the Sun.
• It has a faint ring system and 27 known moons.
• Uranus’s atmosphere is made primarily of hydrogen, helium, and methane, which gives it a blue-green color.
• Its largest moon, Miranda, has a surface that is covered in strange, tectonic features.
• Uranus’s day is just over 17 hours long.
• It is named after the Greek god of the sky.
• Uranus was the first planet discovered using a telescope, by William Herschel in 1781.
• The Voyager 2 spacecraft is the only spacecraft to have flown by Uranus, in 1986.
• Uranus is one of the coldest planets in the solar system, with temperatures that can drop to -224°C.
• Its unusual orientation is believed to be the result of a collision with another large object early in its history.

Neptune

• Neptune is the fourth-largest planet in the solar system and is known for its vivid blue color.
• It has a faint ring system and 14 known moons.
• Neptune’s atmosphere is made primarily of hydrogen, helium, and methane, which gives it its blue color.
• Its largest moon, Triton, is believed to have been a captured Kuiper Belt object.
• Neptune’s day is just over 16 hours long.
• Uranus is named after the Roman god of the sea
• Neptune has the strongest winds of any planet in the solar system, with speeds that can reach up to 2,100 kilometers per hour (1,300 miles per hour).
• Its largest moon, Triton, has a surface that is covered in nitrogen ice and geysers that spew nitrogen gas and dust.
• Neptune was discovered using mathematical calculations before it was actually observed through a telescope, in 1846.
• It is one of the four gas giants in the solar system.
• Neptune has been visited by only one spacecraft, NASA’s Voyager 2, in 1989.

Pluto

• Pluto was once considered the ninth planet in the solar system but was reclassified as a dwarf planet in 2006.
• It has a rocky surface covered in frozen nitrogen, methane, and carbon monoxide.
• Pluto has five known moons, the largest of which is Charon.
• It is part of the Kuiper Belt, a region of the solar system that contains many small, icy objects.
• Pluto’s day is just over 6 days long, and its year is over 248 Earth years.
• It was discovered in 1930 by Clyde Tombaugh.
• Pluto has been visited by only one spacecraft, NASA’s New Horizons, in 2015.
• It is the smallest dwarf planet in the solar system.
• Pluto is named after the Roman god of the underworld.
• Its classification as a planet has been a topic of debate among astronomers and the public.

Other dwarf planets

• There are five officially recognized dwarf planets in the solar system: Pluto, Ceres, Eris, Haumea, and Makemake.
• Ceres is the largest object in the asteroid belt between Mars and Jupiter and was the first dwarf planet to be discovered.
• Eris is the largest known dwarf planet and is part of the scattered disk, a region of the solar system that contains many small, icy objects.
• Haumea is an elongated, egg-shaped dwarf planet that is part of the Kuiper Belt.
• Makemake is the second-brightest dwarf planet after Pluto and is also part of the Kuiper Belt.
• All of the dwarf planets have unique characteristics and features that make them interesting targets for exploration and study.
• The classification of these objects as dwarf planets has helped to refine our understanding of the solar system and its composition.
• The discovery of these dwarf planets has also highlighted the importance of continuing to search for and study small, distant objects in the solar system.

Our Solar System Quiz Questions and Answers

Feel free to use these questions in your own quiz!

1. What is the center of our solar system? A. Earth B. The Moon C. The Sun D. Mars

Answer: C

2. What are the four inner planets of the solar system called? A. The gas giants B. The rocky planets C. The dwarf planets D. The moons

Answer: B

3. Which planet is known as the “Red Planet”? A. Earth B. Venus C. Mars D. Mercury

Answer: C

4. What is the largest planet in the solar system? A. Jupiter B. Saturn C. Uranus D. Neptune

Answer: A

5. What are the outer planets of the solar system called? A. The gas giants B. The rocky planets C. The dwarf planets D. The moons

Answer: A

6. Which planet is closest to the Sun? A. Mars B. Venus C. Earth D. Mercury

Answer: D

7. Which dwarf planet was once considered a planet? A. Ceres B. Pluto C. Eris D. Makemake

Answer: B

8. What is the largest object in the asteroid belt between Mars and Jupiter? A. Pluto B. Eris C. Ceres D. Makemake

Answer: C

9. What is the age of our solar system believed to be? A. 10,000 years B. 1 billion years C. 4.6 billion years D. 100 billion years

Answer: C

10. Which NASA missions have explored the outer planets? A. Apollo missions B. Mercury missions C. Voyager missions D. Mars missions

Answer: C