How many planets are in our solar system?
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Answer
Eight
Eight: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The count dropped from nine in 2006, when Pluto was reclassified.
Space and Planets
Planets, the Moon, seasons, stars and famous missions
Space and Planets is a Bertopia flashcard pack of 69 cards: planets, the Moon, seasons, stars and famous missions. It covers the planets; the Moon; day, night and seasons; the Sun and stars; famous missions.
Sample cards
Where does moonlight come from?
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Answer
Sunlight bouncing off the Moon
The Moon makes no light of its own. Moonlight is sunlight reflected off its surface.
What causes day and night?
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Answer
Earth spinning
Earth spins once about every 24 hours. The side facing the Sun has day, the side facing away has night.
What is the Sun?
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Answer
A star
The Sun is a star, a hot glowing ball of hydrogen and helium. It is a yellow dwarf.
What was Sputnik 1, launched in 1957?
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Answer
The first artificial satellite to orbit Earth
The Soviet Union launched Sputnik 1 on 4 October 1957. It was a metal ball about 56 cm (22 inches) wide that circled Earth every 96 minutes.
Which planet is closest to the Sun?
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Answer
Mercury
Mercury is first in line, only about 0.4 times Earth's distance from the Sun. Venus comes second.
Sources
29 sources
- Planets, NASA Science
- Mercury: Facts, NASA Science
- Venus: Facts, NASA Science
- Earth: Facts, NASA Science
- Mars: Facts, NASA Science
- Jupiter: Facts, NASA Science
- Saturn: Facts, NASA Science
- Uranus: Facts, NASA Science
- Neptune: Facts, NASA Science
- Kuiper Belt: Facts, NASA Science
- Earth's Moon: Facts, NASA Science
- Moon Phases, NASA Space Place
- Tides, NOAA National Weather Service JetStream
- What Causes the Seasons?, NASA Space Place
- How Long Is One Day on Other Planets?, NASA Space Place
- Sun: Facts, NASA Science
- How Old Is the Sun?, NASA Space Place
- Stars, NASA Science
- APOD 2026 October 22: The First Green Star, NASA Science
- The Nearest Neighbor Star, NASA Goddard, Imagine the Universe!
- Sputnik and the Origins of the Space Age, NASA History Office
- Yuri Gagarin: First Human in Space, NASA Science
- July 20, 1969: One Giant Leap for Mankind, NASA History Office
- Voyager, NASA Science
- Voyager 2, NASA Science
- New Horizons, NASA Science
- The History of Hubble, NASA Science
- James Webb Space Telescope, NASA Science
- Mars 2020: Perseverance Rover, NASA Science
