Jupiter
Jupiter is the fifth planet from the Sun and by far the largest planet in our solar system. More than 1,300 Earths could fit inside it, and its mass is greater than all other planets combined. Jupiter's iconic Great Red Spot is a storm so large that Earth could fit inside it.
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- Diameter
- 142,984 km
- Mass
- 317.8 Earths
- Distance from Sun
- 5.203 AU
- Surface gravity
- 24.79 m/s²
- Average temperature
- -110°C
- Known moons
- 95
- Orbital period
- 11.9 Earth years
- Rotation period
- 9.9 hours
- Ring system
- Yes
Source: NASA Planetary Fact Sheets (nssdc.gsfc.nasa.gov)
Atmosphere
Hydrogen (89.8%) and helium (10.2%). Bands of ammonia ice clouds, water vapor, and ammonium hydrosulfide.
In Depth
Jupiter is a gas giant with no solid surface — what we see are the tops of its thick cloud layers. The planet is composed primarily of hydrogen and helium, similar to the Sun, and if it had been about 80 times more massive, it would have become a star. Jupiter's colorful bands are created by powerful jet streams blowing in alternating directions at speeds up to 360 km/h. The Great Red Spot is an anticyclonic storm that has been observed since at least 1831 and possibly since 1665; it is currently about 1.3 times the width of Earth, though it has been shrinking. Deep beneath the clouds, extreme pressure compresses hydrogen into a liquid metallic state, generating the most powerful magnetic field of any planet. This magnetosphere is so large that if it were visible, it would appear larger than the Moon in Earth's sky. Jupiter's four Galilean moons — Io, Europa, Ganymede, and Callisto — are worlds in their own right. Europa likely harbors a global ocean beneath its icy crust, making it a prime target in the search for extraterrestrial life. Jupiter acts as a cosmic shield, its gravity deflecting or capturing many asteroids and comets that might otherwise strike the inner planets.
Notable Features
- 01
The Great Red Spot — a massive anticyclonic storm larger than Earth, raging for centuries
- 02
The strongest magnetic field of any planet, 20,000 times stronger than Earth's
- 03
At least 95 known moons, including the four large Galilean moons
- 04
A faint ring system discovered by Voyager 1 in 1979
Exploration & Missions
Pioneer 10 (1973) and Pioneer 11 (1974) made the first flybys. Voyager 1 and 2 (1979) discovered Jupiter's faint rings and active volcanoes on Io. NASA's Galileo orbiter (1995-2003) dropped a probe into Jupiter's atmosphere and made detailed studies of the Galilean moons. Juno, which arrived in 2016, continues to orbit Jupiter, studying its interior structure, magnetic field, and polar regions. ESA's JUICE mission (launched 2023) is en route to study Jupiter's icy moons, particularly Ganymede. NASA's Europa Clipper (launched 2024) will make detailed flybys of Europa to assess its habitability.
Fun Facts
Jupiter has the shortest day of any planet — it completes one rotation in just under 10 hours despite being 11 times wider than Earth.
Jupiter's mass is 2.5 times that of all other planets in the solar system combined.
Jupiter's moon Ganymede is larger than the planet Mercury.
Jupiter's Great Red Spot has been shrinking: it was once three times the width of Earth.
Frequently Asked Questions
Is Jupiter a failed star?▾
Jupiter is sometimes called a 'failed star' because it is made of the same elements (hydrogen and helium), but this is misleading. Jupiter would need to be about 80 times more massive to sustain hydrogen fusion and become even the smallest type of star (a red dwarf). However, Jupiter does emit about twice as much heat as it receives from the Sun, likely from slow gravitational contraction.
How many moons does Jupiter have?▾
As of 2024, Jupiter has 95 confirmed moons. The four largest — Io, Europa, Ganymede, and Callisto — were discovered by Galileo in 1610 and are visible through a basic telescope. Most of the smaller moons are irregular satellites likely captured by Jupiter's gravity.
What is the Great Red Spot?▾
The Great Red Spot is a persistent high-pressure anticyclonic storm in Jupiter's southern hemisphere. It has been continuously observed for at least 190 years and possibly over 350 years. Winds at the edges reach about 430 km/h. The storm is currently about 16,000 km wide (larger than Earth) but has been gradually shrinking over the past century.
Learn More
The 8 Planets in Order: An Interactive Guide for Students — an in-depth article covering all 8 planets, with size comparisons and learning activities.
Data source: NASA Planetary Fact Sheets
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