Jupiter's magnetic field is so powerful that a compass would react to it from 3 million kilometers away.

Jupiter's magnetosphere is the largest structure in the solar system, extending up to 3 million kilometers toward the Sun and over 1 billion kilometers behind the planet. This immense field is generated by the 'dynamo effect' within a thick layer of liquid metallic hydrogen located about 15,000 kilometers below the planet's surface. At the extreme pressures found deep inside Jupiter, hydrogen acts like a metal, conducting electricity and generating a magnetic field as the planet rotates rapidly every 10 hours.NASA's Juno mission, which arrived at Jupiter in July 2016, has provided the most detailed measurements of this field to date. The spacecraft discovered that the magnetic field is not uniform but is surprisingly 'lumpy' and stronger in the northern hemisphere. The surface magnetic field strength is approximately 7.766 Gauss, which is significantly higher than Earth's field of about 0.25 to 0.65 Gauss. This disparity explains why Jupiter's influence extends so far into deep space.The magnetic field also creates a lethal environment by trapping charged particles from the solar wind and volcanic debris from the moon Io. These particles are accelerated to nearly the speed of light, forming radiation belts that are millions of times more intense than Earth's Van Allen belts. Spacecraft like the Galileo probe and the current Juno mission require heavy titanium shielding to survive these conditions. Without this protection, the high-energy electrons would instantly fry the sensitive silicon chips used in modern navigation and communication systems.