The Heliosphere: Our Shield in Space

While you’re having your morning coffee, contemplate this: the only thing protecting you and your coffee mug from the vast pressures of the interstellar medium is the heliosphere.

That’s a bubble around our Solar System produced by plasma ejected from the Sun’s hot corona at speeds up to 800 km per second. This “solar wind” protects the Solar System and everything in it from the pressures and gasses of the interstellar medium, which is what fills up the space between stars.

The heliosphere stops at a point called quite appropriately termination shock. Beyond that lies the transition to the outer boundary of the system, a zone called the heliosheath. Beyond that, the heliopause marks the actual end of the heliosphere’s reach. And farther out than that? We’re about to find out.

In August 2012 NASA’s intrepid Voyager I spacecraft, launched back in 1977 to explore the outer planets and the farther reaches of the Solar System, became the first and only human made object to penetrate the heliosphere and head out into what lies beyond.

Pushing at a solar wind up to 40 times stronger than in the inner solar system, Voyager reached termination shock and kept on going. Now renamed the Voyager Interstellar Mission, Voyager 1 and voyager 2, which will also cross the heliopause, aim to give earthbound scientists a detailed look at the boundaries of the Solar System and what fills the interstellar medium beyond.

As you sip that cup of coffee in the sunlight streaming through your window, hot plasma from the star that lights your morning creates the envelope that keeps you safe. And Voyager 1 slips silently through the icy blackness of space to find out how that works.

first published at Black Moon Journal