As you examine this tactile, proceed to the far left hand side. As you explore the left side of the tactile, the circle in the middle represents the sun. The tactile is not to scale by size or distance, but serves as a model to represent the heliosphere. The heliosphere is a bubble around our solar system that the edge of which forms its boundary.

Moving away from the sun you will notice a ring and a bump, which represents Pluto and its orbit.

Moving out from Pluto, you'll notice the texture on the tactile is like small ridges radiating away from the sun. Those ridges represent the solar wind. The solar wind is made up of charged particles that are moving away from the sun. The sun is always giving off these charged particles. The pressure of these particles moving away from the sun weakens the further away from the sun they get. At a point about two and a half times the distance of Pluto, the pressure of these charged particles is low enough so that the interaction between interstellar space begins to affect the movement of particles. This point is called the termination shock. You can feel the termination shock as a ring of beads beyond Pluto's orbit.

Just beyond the termination shock, the texture changes drastically. This area is called the heliosheath. Particles no longer move smoothly away from the sun. They are moving turbulently as they are affected by interstellar space.

As we move on, you will touch another ring called the heliopause. As you run your finger along the heliopause, you'll notice that it's somewhat oval shaped and ends abruptly at the vertical line separating the tactile and our key. In this tactile, the entire solar system is moving from right to left. This movement creates the blunt nose on the heliopause. Pressure from interstellar space also pushes part of the heliopause backwards, away from the sun. Scientists think that the heliosphere may have a tail like a comet, but we are not sure exactly what it looks like.

Further to the left, on the outer edge of the tactile, you will feel the bow shock. The bow shock is the "bunching up" of interstellar gas and dust, called interstellar medium as the solar system moves through it. Some people compare it to the bow, or front part of a boat, pushing the water out and around it as it moves through the water.

As you proceed to the far right hand side of the tactile, you will find a key describing the various parts of the heliosphere on the lower right. On the upper right is the IBEX mission logo.

Artists have used the wordplay between the acronym for Interstellar Boundary Explorer and the animal called the ibex when designing the logo. The ibex animal - a mountain goat with curved horns - is on the left hand side of the logo. Its horns form part of the representation of the boundary of the solar system in the logo. The boundary of our solar system is what the IBEX spacecraft will investigate. You can learn more about the IBEX spacecraft by exploring the tactile image and audio description of it.

You can learn more about the mission and the heliosphere by visiting the IBEX web site at www.ibex.swri.edu.