New IBEX data show heliosphere’s long-theorized bow shock does not exist
New results from NASA’s Interstellar Boundary Explorer (IBEX) reveal that the bow shock, widely accepted by researchers to precede the heliosphere as it plows through tenuous gas and dust in interstellar space (similar to the sonic boom made by a jet breaking the sound barrier), does not exist.
The latest refinements in relative speed and local interstellar magnetic field strength prevent the heliosphere, the magnetic “bubble” that cocoons Earth and the other planets, from developing a bow shock. The bow shock would consist of ionized gas or plasma that abruptly and discontinuously changes in density in the region of space that lies straight ahead of the heliosphere.
For about a quarter-century, researchers believed that the heliosphere moved through the interstellar medium at a speed fast enough to form a bow shock. IBEX data have shown that the heliosphere actually moves through the local interstellar cloud at about 84,000 km/h, roughly 11,000 km/h slower than previously thought — slow enough to create more of a bow “wave” than a shock.
While bow shocks certainly exist ahead of many other stars, we’re finding that our Sun’s interaction doesn’t reach the critical threshold to form a shock, so a wave is a more accurate depiction of what’s happening ahead of our heliosphere — much like the wave made by the bow of a boat as it glides through the water.
Above: The heliosphere is the region of space dominated by the Sun that cocoons Earth and the other planets. Inflated by the million-mile-per-hour solar wind, the bubble-shaped heliosphere pushes its way through the galaxy.