Astronomy facts for active recall
Solar System Planets And Facts
Learn the eight planets in order, compare rocky and giant planets, and explore dwarf planets, major moons, and the regions beyond Neptune.
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From the Sun outward
Planets In Order
Recall the eight planets by their position from the Sun.
Prompt
Which planet is first from the Sun?
Answer
Mercury
Prompt
Which planet is second from the Sun?
Answer
Venus
Prompt
Which planet is third from the Sun?
Answer
Earth
Prompt
Which planet is fourth from the Sun?
Answer
Mars
Prompt
Which planet is fifth from the Sun?
Answer
Jupiter
Prompt
Which planet is sixth from the Sun?
Answer
Saturn
Prompt
Which planet is seventh from the Sun?
Answer
Uranus
Prompt
Which planet is eighth from the Sun?
Answer
Neptune
Inner solar system
The Rocky Planets
Review defining facts about Mercury, Venus, Earth, and Mars.
Prompt
Which four planets are terrestrial, or rocky, planets?
Answer
Mercury, Venus, Earth, and Mars
Prompt
Which is the smallest planet?
Answer
Mercury
Prompt
Which planet is the hottest?
Answer
Venus
Prompt
Which planet is the only known world with life?
Answer
Earth
Prompt
Which planet is known as the Red Planet?
Answer
Mars
Prompt
Which rocky planets have no moons?
Answer
Mercury and Venus
Prompt
Which rocky planet has two small moons?
Answer
Mars
Prompt
Which rocky planets have substantial atmospheres?
Answer
Venus, Earth, and Mars
Outer solar system
The Giant Planets
Compare Jupiter, Saturn, Uranus, and Neptune.
Prompt
Which two planets are gas giants?
Answer
Jupiter and Saturn
Prompt
Which two planets are ice giants?
Answer
Uranus and Neptune
Prompt
Which is the largest planet?
Answer
Jupiter
Prompt
Which planet is famous for its prominent ring system?
Answer
Saturn
Prompt
Which planet rotates on its side?
Answer
Uranus
Prompt
Which planet is farthest from the Sun?
Answer
Neptune
Prompt
Which four planets have ring systems?
Answer
Jupiter, Saturn, Uranus, and Neptune
Prompt
Which planet has the Great Red Spot?
Answer
Jupiter
Small worlds
The Five Named Dwarf Planets
Learn the five dwarf planets highlighted by NASA.
Prompt
Which dwarf planet lies in the asteroid belt?
Answer
Ceres
Prompt
Which famous former ninth planet is now classified as a dwarf planet?
Answer
Pluto
Prompt
Which dwarf planet rotates unusually quickly and has an elongated shape?
Answer
Haumea
Prompt
Which dwarf planet is named after a Rapa Nui creation deity?
Answer
Makemake
Prompt
Which dwarf planet's discovery helped prompt debate about Pluto's classification?
Answer
Eris
Prompt
What are the five dwarf planets highlighted by NASA?
Answer
Ceres, Pluto, Haumea, Makemake, and Eris
Beyond the planets
Moons And Solar-System Regions
Review major moons and the regions where smaller bodies orbit.
Prompt
What is the largest moon in the solar system?
Answer
Ganymede, a moon of Jupiter
Prompt
Which moon has a thick atmosphere and methane lakes?
Answer
Titan, a moon of Saturn
Prompt
Which moon is known for a likely ocean beneath its icy surface?
Answer
Europa, a moon of Jupiter
Prompt
Which moon orbits Neptune backward relative to Neptune's rotation?
Answer
Triton
Prompt
Where is the main asteroid belt?
Answer
Between Mars and Jupiter
Prompt
What is the Kuiper Belt?
Answer
A region of icy bodies beyond Neptune
Prompt
What is the Oort Cloud thought to be?
Answer
A distant spherical shell of icy bodies surrounding the solar system
Prompt
What holds the solar system together?
Answer
The Sun's gravity
How To Practise
Start by recalling the planets in order. Then learn one family at a time: rocky planets, giant planets, dwarf planets, and finally moons and regions.
Source Note
The classifications and core facts follow NASA Solar System Exploration, its dwarf-planet overview, and NASA's individual world profiles. Moon counts are deliberately omitted because new discoveries can change them.
FAQ
How many planets are in the solar system?
There are eight planets orbiting the Sun.
What are the planets in order from the Sun?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
Is Pluto a planet?
Pluto is classified as a dwarf planet. It was reclassified by the International Astronomical Union in 2006.