Heliosphere (image) University of California - Berkeley Caption STEREO detected energetic neutral atoms (ENAs) from the edge of the solar system, where the solar wind meets the interstellar medium. Hot ions in the heliosheath -- the region between the termination shock and heliopause -- are uniquely traced by ENAs and are more intense (indicated by color code) around the nose of the heliosphere, with an asymmetric double peak. The twin STEREO A and B spacecraft are shown in the sun-centered orbit they share with Earth. Last year, the Voyager 2 spacecraft passed into the heliosheath, joining Voyager 1. There, these interstellar explorers continue their journey into the farthest reaches of the heliosphere. Credit University of California, Berkeley; L. Wang Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.