Jupiter

The largest planet in the Solar System.

Jupiter was discovered by ancient civilizations in ancient times. However, first detailed observations of it were made by Galileo Galeli, in 1610, by a telescope made by Galileo himself.

Galileo sketch of Jupiter with early observations — Galileo’s sketches of the moons of Jupiter made on the nights of February 3 and 4, 1610. (Ori means Orient, or East, Occ Occident, or West). Image Credit: Octavo Corp./Warnock Library)

Galileo sketch of Jupiter showing changing positions of its moons — Galileo’s sketches of the moons of Jupiter made on the nights of February 3 and 4, 1610. (Ori means Orient, or East, Occ Occident, or West). Image Credit: Octavo Corp./Warnock Library)

He laid out sketches of what he saw, 4 bright dots next to the large brightness in the middle. These bright dots would later come out to be the largest moons of Jupiter.

Jupiter’s scale is almost overwhelming, its diameter is about 143,000 km, more than 11 times that of Earth, and its volume is so vast that over 1,300 Earths could fit inside it.

Jupiter's Great Red Spot — Jupiter’s Great Red Spot, photographed by Juno.

Jupiter hosts one of the largest storms ever observed by humanity. Its size is so immense that it can engulf the entire Earth (about 16,000 km wide), larger than our planet’s diameter.

Jupiter’s 4 largest moons (sizes scaled up 10× for visibility).

Jupiter has 95 known moons, making it the planet with the most satellites in our Solar System; among them are the four Galilean moons—Io, Europa, Ganymede, and Callisto.

Jupiter’s 4 largest moons. Sizes and distances to scale.

If the sizes of the moon and the distance between the planet were kept to scale, the moons would hardly be visible. This explains why Galileo needed to build a telescope of his own to observe these moons.