than 650 million kilometres (past the orbit of Saturn). Many of the moons of Jupiter lie within its magnetosphere. The magnetic field contains high levels of radiation and energetic particles, so entering the region it covers would be fatal to space travellers. The Galileo probe discovered a new intense radiation belt between Jupiter's rings and the uppermost atmospheric layers. This belt is about 10 times more intense than Earth's Van Allen radiation belts, and contains high-energy helium ions.

Jupiter emits radio waves strong enough to be picked up by radiotelescopes on Earth. Scientists have used these waves to calculate the rotational speed of Jupiter. The strength of the waves varies as the planet rotates and is influenced by Jupiter's magnetic field. The radio waves come in two forms. The first of these is a continuous emission from Jupiter's surface; the second is a strong burst that occurs when the moon Io passes through certain regions of the magnetic field and radiation belt.

X-ray telescopes and the Hubble Space Telescope regularly detect auroras on Jupiter. These auroras are thousands of times more powerful than those on Earth. On Earth, the most intense auroras are caused by outbursts of charged particles from the Sun interacting with the polar magnetic field of Earth. On Jupiter, however, the particles seem to come from the moon Io, which has volcanoes that spew out oxygen and sulfur ions. Jupiter's strong magnetic field produces about 10 million volts around its poles, and this field captures the charged particles and slams them into the planet's atmosphere. The particles interact with molecules in the atmosphere and the result is intense X-ray auroras, virtually all the time.

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