Evidence of the giant planets’ magnetospheres comes from spacecraft in the outer Solar System, from telescopes orbiting Earth, and from radio emissions received on Earth. Rapidly moving electrons in planetary magnetospheres spiral around the direction of the magnetic field, and as they do so they emit synchrotron radiation, as discussed in Connections 10.1. If your eyes were sensitive to radio waves, then the second-brightest object in the sky would be Jupiter’s magnetosphere. The Sun would still be brighter, but it would not appear larger than Jupiter’s magnetosphere; even at a distance from Earth of 4.2–6.2 AU, Jupiter’s magnetosphere would appear roughly twice as large as the Sun in the sky. Saturn’s magnetosphere would also be large enough to see, but it would be much fainter than Jupiter’s. Even though Saturn has a strong magnetic field, pieces of rock, ice, and dust in Saturn’s spectacular rings act like sponges, soaking up magnetospheric particles soon after those particles enter the magnetosphere. With far fewer magnetospheric electrons, there is much less radio emission from Saturn.