Jupiter

Jupiter: The Largest Planet in the Solar System

Jupiter is the largest planet in the solar system by a long way. If you combined the mass of every other planet, Jupiter would still outweigh them all by more than two to one. It's the fifth planet from the Sun, and has been visible to humans throughout history — bright enough to cast a shadow on Earth on its best nights.

Named after the king of the Roman gods, Jupiter is a gas giant with no solid surface. Its atmosphere is mostly hydrogen and helium, banded into cloud belts by its rapid 10-hour rotation. Below the clouds, pressures build until the hydrogen becomes liquid — and possibly metallic.

The Galilean Moons: Io, Europa, Ganymede and Callisto

Jupiter has four large moons: Io, Europa, Ganymede and Callisto. These are called the Galilean moons after Galileo Galilei, who first observed them in 1610. They were the first moons discovered orbiting a planet other than Earth, and their existence helped confirm that not everything in the solar system orbits the Earth.

Ganymede is the largest moon in the solar system — bigger than the planet Mercury. Europa has a global ocean of liquid water beneath its icy crust, making it one of the most promising places to search for life beyond Earth. Io is the most volcanically active body in the solar system. Callisto's surface is the most heavily cratered of any object we've mapped.

How Many Moons Does Jupiter Have?

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 no more than a few kilometres across. These irregular moons are likely captured asteroids or fragments from ancient collisions pulled in by Jupiter's gravity.

In March 2026, the Minor Planet Center confirmed four new Jupiter moons — S/2011 J 4, S/2011 J 5, S/2018 J 5, and S/2024 J 1 — discovered by Scott Sheppard's team at the Carnegie Institution for Science using telescopes in Chile and Hawaii. All four belong to known irregular moon families. Read the full story →

The Great Red Spot: Jupiter's Ancient Storm

The Great Red Spot is Jupiter's most recognisable feature — a persistent storm system that has been observed continuously since the 17th century. At its largest it was around three times the width of Earth; today it's roughly Earth-sized after decades of gradual shrinkage.

The storm is an anticyclone — high pressure spinning anticlockwise — with wind speeds at its edges reaching around 640 km/h. NASA's Juno spacecraft, which has been orbiting Jupiter since 2016, has captured the most detailed views ever taken of the storm, revealing swirling cloud structures down to scales of a few kilometres.

Io: The Most Volcanically Active Body in the Solar System

Io is driven by the immense tidal forces Jupiter exerts on it. As Io orbits Jupiter, gravitational squeezing from Jupiter and the other Galilean moons flexes its interior, generating heat that powers hundreds of active volcanoes. The surface is constantly resurfaced by lava flows and sulphur deposits, making it the geologically youngest solid surface in the solar system.

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.

Observing Jupiter in 2026

Jupiter reached opposition on 10 January 2026, when it was at its closest to Earth and at its brightest. As of June 2026, Jupiter is still visible in the evening sky but past its peak — it's getting lower in the west each night. The next Jupiter opposition is 11 February 2027.

Even away from opposition, Jupiter is one of the easiest objects to find in the night sky. It's consistently one of the brightest points of light visible, and its four Galilean moons are accessible with almost any optical aid.