Science News

We tend to think of interstellar journeys as leaps into the void, leaving the security of one solar system to travel non-stop to another. But a number of alternatives exist, a fact that becomes clear when we ponder that our own cloud of comets — the Oort Cloud — is thought to extend a light year out and perhaps a good deal further. There may be ways, in other words, to take advantage of resources like comets and other icy objects for a good part of an interstellar trip. That scenario is not as dramatic as a starship journey, but it opens up possibilities.

A great magnetic bubble surrounds the solar system as it cruises through the galaxy. The sun pumps the inside of the bubble full of solar particles that stream out to the edge until they collide with the material that fills the rest of the galaxy, at a complex boundary called the heliosheath. On the other side of the boundary, electrically charged particles from the galactic wind blow by, but rebound off the heliosheath, never to enter the solar system. Neutral particles, on the other hand, are a different story. They saunter across the boundary as if it weren't there, continuing on another 7.5 billion miles for 30 years until they get caught by the sun's gravity, and sling shot around the star.

Animation of the interstellar interaction with our Sun - one of billions of stars that orbits around the galaxy. As we zoom in through the galaxy we can see our heliosphere; then if we travel along with the interstellar material, we can see how only a very rare few are directed along precisely the right path to make the 30 year, 15 billion mile journey and enter IBEX's low energy sensor and be detected.