Space Weather throughout the Solar System
The Sun is surrounded by a "bubble" in space called the heliosphere. In a sense, we Earthlings live within the outer atmosphere of our Sun. The solar wind fills the heliosphere with energetic particles and magnetic fields, extending the outermost reaches of the solar atmosphere well beyond the orbit of Pluto. The heliopause is the boundary where the influence of the solar wind finally wanes and interstellar space truly begins. Instruments on interplanetary spacecraft help us probe the heliosphere, while those same spacecraft are at risk from damage by space weather storms. Some day astronauts will venture far from Earth, and their safety will depend upon our knowledge of radiation throughout the heliosphere.
Within the heliosphere, the solar wind interacts with planets, moons, and other smaller bodies in our Solar System. Some planets possess strong global magnetic fields that interact with the solar wind. This interplay gives rise to complex, dynamic systems of radiation belts, flows of electrical currents, and auroral displays in the neighborhoods of such planets. Planets lacking magnetic fields are left unshielded from bombardment by the solar outpourings. A few moons have magnetic fields and magnetospheres as well, though most do not. Comets, with their long tails of dust and ionized gases, are the bodies most visibly influenced by the solar wind.
Stars, and the planetary systems that surround them, change over time. Our Sun, though dimmer, was more active in its infancy. The strong solar wind of our Sun's youthful stage swept away the leftover dust after the planets had formed. In recent years we have become able to observe the heliospheres of other stars, helping us learn about our own Sun via comparison. Early, active phases of a star's life exert a powerful influence over the formation of planets in their vicinity. Likewise, the outpouring of energy during the death throes of older stars, especially in cases that lead to nova and supernova explosions, can influence the development of other stellar systems over distances of many light years.