The Cassini spacecraft observes the interaction between the solar wind and Saturn's magnetic field in this artist's concept. Saturn's magnetic field, which is generated by the planet's rotation, extends far into space. But as the solar wind hits the magnetic field (a region depicted in blue), it pushes the field toward Saturn on the Sun-facing side, and far into space on the Sun-trailing side. This can leave some of Saturn's moons exposed to the full force of solar radiation and particles for parts of their orbits, as they circle outside the protective magnetic field. [NASA/JPL]
Moon and Saturn
The giant planets of the outer solar system are encircled by giant entourages of moons. Saturn, for example, has more than 60 known moons. The planets protect the moons by enfolding them in their own magnetic fields - some of the time.
Saturn’s magnetic field is generated deep within the planet itself.
Saturn’s core is a dense knot of rock and metal. It’s surrounded by a thick layer of hydrogen that’s squeezed so tightly that it acts like a metal. The core and the metallic hydrogen rotate at different rates, generating an electric dynamo that produces the magnetic field.
Saturn’s magnetic field is hundreds of times stronger than Earth’s. It deflects much of the solar wind - a flow of charged particles from the Sun - as well as cosmic rays, which are particles from outside the solar system.
But the solar wind sculpts the realm of Saturn’s magnetic influence into a teardrop shape. The region that faces the Sun is squeezed in toward Saturn, while the region away from the Sun forms a tapered tail that extends millions of miles into space.
So depending on how far it is from Saturn, a moon may be protected when it’s on one side of the planet, but unprotected on the other - and subject to the full force of the solar wind.
Look for Saturn near our own moon tonight. The planet looks like a bright golden star. It’s a little to the left of the Moon as they climb into view around midnight, and above the Moon at first light tomorrow.
Script by Damond Benningfield, Copyright 2013
For more skywatching tips, astronomy news, and much more, read StarDate magazine.