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The Solar System, Explained
No telescope required. These ten questions cover the essentials of our cosmic neighbourhood — and a few facts that surprise almost everyone.
About this topic
Our solar system is a handful of planets and a great deal of empty space, all held in place by the Sun, which holds more than 99 percent of the whole system's mass. This quiz covers the essentials and a few facts that surprise most people: that Venus, not Mercury, is the hottest planet because of a runaway greenhouse effect; that Jupiter is more massive than every other planet combined; that Uranus rolls around its orbit tipped almost on its side. You will meet the largest moon, Ganymede, which is bigger than the planet Mercury, and Pluto, reclassified as a dwarf planet in 2006. None of it needs a telescope or a physics degree, and every answer comes with a short explanation of why it is true.
Questions & answers
The Solar System, Explained: all 10 questions and answers
Every question in this quiz is listed below with its correct answer and the reasoning behind it. Play first if you would rather not see the answers — or read through as a study sheet.
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1Which planet is closest to the Sun?
- A Earth
- B Venus
- C Mercury Correct
- D Mars
Answer: C. Mercury
Why: Mercury orbits at an average distance of about 58 million kilometres from the Sun.
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2Which is the largest planet in the solar system?
- A Saturn
- B Neptune
- C Jupiter Correct
- D Earth
Answer: C. Jupiter
Why: Jupiter is so massive that its mass is more than twice that of all the other planets combined.
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3Which planet is known as the Red Planet?
- A Jupiter
- B Mars Correct
- C Mercury
- D Venus
Answer: B. Mars
Why: Iron oxide — essentially rust — on its surface gives Mars its reddish colour.
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4Which planet has the most prominent ring system?
- A Neptune
- B Jupiter
- C Uranus
- D Saturn Correct
Answer: D. Saturn
Why: Saturn's bright rings are made mostly of countless pieces of ice and rock.
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5What is the largest moon in the solar system?
- A Ganymede Correct
- B Titan
- C The Moon
- D Europa
Answer: A. Ganymede
Why: Ganymede, a moon of Jupiter, is even larger than the planet Mercury.
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6Which planet rotates on its side?
- A Neptune
- B Uranus Correct
- C Saturn
- D Mars
Answer: B. Uranus
Why: Uranus has an axial tilt of about 98 degrees, so it essentially rolls around its orbit.
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7What lies at the centre of the solar system?
- A Jupiter
- B The Sun Correct
- C A black hole
- D Earth
Answer: B. The Sun
Why: The Sun holds about 99.8% of the entire system's mass, keeping everything in orbit.
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8Which is the hottest planet in the solar system?
- A Mars
- B Jupiter
- C Mercury
- D Venus Correct
Answer: D. Venus
Why: A runaway greenhouse effect makes Venus hotter than Mercury, with surface temperatures around 465°C.
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9Which object was reclassified as a dwarf planet in 2006?
- A Makemake
- B Ceres
- C Eris
- D Pluto Correct
Answer: D. Pluto
Why: The International Astronomical Union redefined "planet" in 2006, reclassifying Pluto as a dwarf planet.
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10Roughly how long does sunlight take to reach Earth?
- A About 8 seconds
- B About 8 minutes Correct
- C About 8 hours
- D Instantly
Answer: B. About 8 minutes
Why: Light travels the roughly 150 million km from the Sun to Earth in about 8 minutes and 20 seconds.
Frequently asked questions about The Solar System, Explained
How many questions are in The Solar System, Explained?
The Solar System, Explained has 10 questions and takes about 6 minutes to finish. It is rated Easy and sits in our Science & Nature category.
How is The Solar System, Explained scored?
Each of the 10 correct answers adds 10 XP, up to 100 XP for a clean run. Wrong answers cost you nothing, and your full question-by-question review is shown at the end.
Are the answers to The Solar System, Explained explained?
Yes. All 10 questions carry a written explanation of why the correct answer is right, so the quiz works as a study sheet as well as a test.
Can I replay The Solar System, Explained?
Yes, as often as you like. The questions and the answer options are reshuffled on each run, and you can use Practice Mistakes afterwards to retry only the ones you missed. No account is needed to play.
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