God Of The Night Sky!

Jupiter is the king of the planets. Fifth from the Sun, but containing 2 ½ times the mass of all the others combined! If it was much bigger, it may have become a small star! Jupiter is covered with swirling bands of clouds and an Earth-sized storm called the Great Red Spot. Being a gas giant, the planet is mainly composed of hydrogen and helium. Jupiter is also home to the Galilean moons – Io, Europa, Ganymede and Callisto.


Fast Summary Facts About Jupiter!

  • Name Origin: Roman god of the sky & lightening
  • Average Diameter: 139,800 km (86,900 miles)
  • Planet Rank: Largest
  • Number of Moons: 69 known moons
  • Surface Gravity: 2.53 g
  • Orbital Radius: 5.2 AU
  • Orbital Period: 11.9 years (4,332 days!)
  • Rotational Period: 9 hours 55 ½ minutes
  • Axial Tilt: 3.1°
  • Atmosphere: Composed of hydrogen & helium
  • Surface Temperature: -110 °C (163 K)

Cool Facts About The Solar System’s Giant Planet!

  • Jupiter has been known since ancient times and is typically the third brightest object in the night sky after the Moon and Venus.
  • Jupiter has over 318 times the mass of Earth, but if it was 75 times more massive, nuclear fusion in its core would begin turning the gas giant into a star!
  • Despite being only 0.1% the mass of the Sun, the centre of gravity between it and the Sun lies just above the Sun's surface. This is the only planet for which this is true.
  • Jupiter is 11 times wider than Earth and over 1,320 Earth’s are able to fit inside the gas giant.
  • Despite being the biggest planet in the solar system, it has the shortest day, completing an orbit every 9 hours and 55 minutes. This causes it to have a slightly ‘flattened’ shape.
  • Jupiter spins nearly upright as it orbits the Sun, so doesn’t experience seasons like the other planets do.
  • The planet is believed to have a solid core of heavy elements, but is mostly made up of swirling gases and fluids like hydrogen and helium (similar to what the Sun is made of).
  • Jupiter’s appearance is dominated by uniquely colourful bands of cloud and swirling spots. Many of the bands move in opposite directions to one another.
  • The ‘Great Red Spot’ is a gigantic storm which has been ragging since detailed observations of Jupiter were first made nearly 200 years ago.
  • Jupiter is orbited by at least 69 moons, most small captured asteroids, but the four Galilean moons are among the most interesting in the solar system!
    • The innermost Galilean moon ‘Io’ is the most volcanic object in the solar system!
    • The bright icy moons Europa and Callisto may harbour deep oceans under their icy crusts.
    • And the biggest of the Galilean moons, Ganymede, is larger than the Planet Mercury!
  • Jupiter is known to have the largest magnetic field of any planet. It is between 15 and 50 times stronger than Earth’s and results in a band of radiation close to the planet which is hazardous to spacecraft.
  • This powerful magnetosphere also creates some of the solar system’s more spectacular auroras near the planet's poles.
  • In 1994, something truly amazing happened to Jupiter. Twenty fragments of the comet Shoemaker-levy 9 collided with the planet. These impacts created enormous explosions and left dark clouds the size of Earth!
  • A total of 9 space probes have visited Jupiter, most making flybys - Pioneer 10&11, Voyager 1, Voyager 2, Ulysses, Cassini-Huygens and New Horizons. Two spacecraft (Galileo & Juno) entered orbit to study Jupiter & its moons up close.
  • Two future missions are planned to visit Jupiter in the 2020’s (ESA’s JUICE & NASA’s Europa Clipper) to study the frozen Galilean moons which may have habitat environments in their subsurface oceans. I can’t wait to see what they discover!
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