Key Takeaways

  • Largest planet in solar system - over 1,300 Earths could fit inside Jupiter
  • Famous Great Red Spot storm has raged for over 300 years
  • Has 101 confirmed moons including the four large Galilean satellites (March 2026)

Table of Contents

The Largest Planet in Our Solar System

Jupiter is the largest planet in our solar system by a long way. If you were to combine all of the other planets in our solar system together, Jupiter would still be over two and a half times bigger! This gas giant dominates the outer solar system with its immense size and powerful gravitational influence.

Named after the supreme god in Roman mythology, Jupiter was the god of the sky, heavens and law. The planet's massive presence in our night sky has inspired astronomers and stargazers for thousands of years.

A Star That Never Was

Jupiter is mainly composed of hydrogen and helium, the same as the Sun. In fact, if Jupiter had formed 80 times bigger than what it is now, it would have become a star rather than a planet.

The Galilean Moons

Jupiter has 4 main moons: Io, Europa, Ganymede and Callisto. Collectively these 4 moons are called the Galilean satellites after the astronomer Galileo Galilei who first discovered them in the year 1610. These massive moons are fascinating worlds in their own right, each with unique characteristics.

Ganymede is the largest moon in our solar system, even larger than the planet Mercury. Europa is believed to have a subsurface ocean that may harbor conditions suitable for life. Io is the most volcanically active body in the solar system, while Callisto's ancient, heavily cratered surface tells the story of our solar system's violent past.

Jupiter's Extensive Moon System

As of March 2026, Jupiter has 101 confirmed moons — the second-highest count of any planet in the solar system, behind Saturn's 285. Beyond the four Galilean moons, most of Jupiter's other satellites are much smaller, usually no more than 4 km across. These irregular moons are likely captured asteroids or fragments from ancient collisions that fell under Jupiter's gravitational influence billions of years ago.

In March 2026, the Minor Planet Center announced four new Jupiter moons — S/2011 J 4, S/2011 J 5, S/2018 J 5, and S/2024 J 1 — discovered by a team led by Scott Sheppard of the Carnegie Institution for Science using data from observatories in Chile and Hawaii. All four belong to known irregular moon families: the Himalaya, Carme, and Ananke groups. Read the full story →

Jupiter's Named Moons (selected)

1. Io
2. Europa
3. Ganymede
4. Callisto
5. Amalthea
6. Himalia
7. Elara
8. Pasiphae
9. Sinope
10. Lysithea
11. Carme
12. Ananke
13. Leda
14. Thebe
15. Adrastea
16. Metis
17. Callirrhoe
18. Themisto
19. Megaclite
20. Taygete
21. Chaldene
22. Harpalyke
23. Kalyke
24. Iocaste
25. Erinome
26. Isonoe
27. Praxidike
28. Autonoe
29. Thyone
30. Hermippe
31. Aitne
32. Eurydome
33. Euanthe
34. Euporie
35. Orthosie
36. Sponde
37. Kale
38. Pasithee
39. Hegemone
40. Mneme
41. Aoede
42. Thelxinoe
43. Arche
44. Kallichore
45. Helike
46. Carpo
47. Eukelade
48. Cyllene
49. Kore
50. S/2003 J2
51. S/2003 J3
52. S/2003 J4
53. S/2003 J5
54. S/2003 J9
55. S/2003 J10
56. S/2003 J12
57. S/2003 J15
58. S/2003 J16
59. S/2003 J17
60. S/2003 J18
61. S/2003 J19
62. S/2003 J23
Jupiter photographed by the James Webb Space Telescope showing glowing auroras at both poles, faint ring system and three moons against a black background
Jupiter imaged by the James Webb Space Telescope in 2022 — auroras glow at both poles, the faint ring system is visible, and three of the Galilean moons appear as bright points to the left. This single image captures more detail than decades of ground-based observation. Credit: NASA / ESA / CSA / STScI / Jupiter ERS Team

The Great Red Spot

The Great Red Spot is Jupiter's most iconic feature — a storm system that has been raging for at least 350 years. At its largest it was three times the width of Earth, though it has been slowly shrinking. NASA's Juno spacecraft, which has been orbiting Jupiter since 2016, has captured the most detailed views of the storm ever taken.

Jupiter's Great Red Spot close-up from NASA Juno spacecraft JunoCam showing swirling orange and brown cloud bands surrounding the ancient storm
The Great Red Spot as seen by Juno's JunoCam during a close flyby — the most detailed view ever captured of Jupiter's centuries-old storm. The swirling clouds surrounding it reach wind speeds of 640 km/h. Credit: NASA / JPL-Caltech / SwRI / MSSS
Jupiter full disc from NASA Juno spacecraft showing banded cloud belts, Great Red Spot and swirling atmospheric features in vivid detail
Jupiter's full disc photographed by the Juno spacecraft in February 2019 — the banded cloud belts, swirling storms, and the Great Red Spot (lower left) are all visible in extraordinary detail. Credit: NASA / JPL-Caltech / SwRI / MSSS / Kevin M. Gill

Io: Jupiter's Volcanic Moon

Io is the most volcanically active body in the solar system, driven by the immense tidal forces Jupiter exerts on it. When New Horizons flew past Jupiter in February 2007 on its way to Pluto, it captured some of the most dramatic images of Io ever taken — including a real-time eruption of the Tvashtar volcano, hurling lava 330 kilometres above the surface.

Jupiter and volcanic moon Io composite image from New Horizons spacecraft showing Tvashtar volcanic plume erupting above Io's surface
Jupiter and Io — a volcanic plume from Tvashtar is clearly visible erupting above Io's limb. Credit: NASA / JHU APL / SwRI
Io moon of Jupiter close-up from New Horizons showing multicoloured volcanic surface with sulphur deposits
Io in detail — the multicoloured surface is painted by sulphur and sulphur dioxide deposits from hundreds of active volcanoes. Credit: NASA / JHU APL / SwRI
🌋 Watch Tvashtar Erupt

New Horizons captured five images over eight minutes showing lava spraying 330km above Io's surface. Click here to watch the Tvashtar eruption animation — one of the most dramatic sequences ever captured in planetary science. Credit: NASA / JHU APL / SwRI