What Is The Smallest Planet And Largest Planet In Our Solar System?

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What Is the Smallest Planet and Largest Planet in our Solar System?

By: Maria Temming July 15, 2014 0

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The smallest planet in our solar system is Mercury and the largest planet is Jupiter.

Smallest Planet: Mercury

There are a couple of different ways to measure how “big” something is. The first is an object’s mass (how much matter it contains) and the second is its volume (how much space it takes up). The smallest planet in regards to both mass and volume is Mercury — at 4,879 km across and 3.3010 x 1023 kg, this tiny world is nearly 20 times less massive than Earth, and its diameter is about 2½ times smaller. In fact, Mercury is closer in size to our Moon than to Earth.

In case you're wondering, though, Mercury is still significantly larger than the dwarf planet Pluto: Pluto's equatorial diameter is just 2,302 km, about half Mercury's width.

Further Reading:

• The Origin of Mercury's "Chaotic Terrain"
• Capturing the 2019 Transit of Mercury
• Bepi-Colombo Mission to Mercury Launches

Hold Mercury in your hand: Sky & Telescope offers a 12-inch Mercury globe based on imagery from NASA's Messenger spacecraft.

Largest Planet: Jupiter

The largest planet in our solar system by far is Jupiter, which beats out all the other planets in both mass and volume. Jupiter’s mass is more than 300 times that of Earth, and its diameter, at 140,000 km, is about 11 times Earth’s diameter. (Jupiter's Great Red Spot, even at its current diminished size, spans 15,900, just over a full Earth diameter.) Jupiter is 2½ times more massive than the rest of the planets in the solar system combined. Despite its bulk, though, Jupiter has a fast rotation period of just 10 hours!

Further Reading:

• Jupiter's Beautiful Polar Cyclones
• Jovian Moons: 79 and Counting
• Jupiter's Weird Magnetic Field
• A Weather Cycle on Jupiter
• Jupiter's "Fuzzy" Core

Planet Size Comparison

Find a "by the numbers" comparison for all the planets courtesy of NASA:

• Mercury
• Venus
• Earth and Moon
• Mars
• Jupiter
• Saturn
• Uranus
• Neptune

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Solar System Solar System FAQ

About Maria Temming

Maria Temming, a previous Sky and Telescope editorial intern, is now earning her Master's in Science Writing at MIT.

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