New Horizons Finds Solar Wind Slows 13%-15% by 58 AU as Interstellar Gas Adds Drag
Updated
Updated · sflorg.com · Jun 30
New Horizons Finds Solar Wind Slows 13%-15% by 58 AU as Interstellar Gas Adds Drag
3 articles · Updated · sflorg.com · Jun 30
Summary
58 AU from the Sun, New Horizons measured solar wind speeds 13% to 15% below levels at 1 AU, mapping a gradual slowdown in the outer heliosphere.
Charge exchange drives that deceleration: incoming interstellar neutral atoms become ionized, add mass to the solar wind, and reduce its speed as it moves outward.
Earlier readings at 30 to 43 AU showed only a 5% to 10% slowdown, while Voyager 2 recorded a much sharper 46% speed drop at the termination shock around 84 AU.
Those measurements help scientists model the heliosphere’s outer boundaries, which regulate how much galactic cosmic radiation can penetrate toward Earth and deep-space missions.
The findings also sharpen forecasts for astronaut and spacecraft radiation exposure on future Moon and Mars missions and offer clues to how other stars’ astrospheres behave.
With our solar wind slowing unexpectedly, what does this reveal about the interstellar space New Horizons is about to enter?
As interstellar particles brake our solar wind, how does this change the radiation threat for future human missions beyond Mars?
How will IMAP's data from Earth's orbit help predict the cosmic ray dangers that deep-space Artemis missions will face?
New Horizons Reveals Major Solar Wind Deceleration at the Solar System’s Edge: Implications for the Heliosphere and Astrospheres
Overview
NASA's New Horizons spacecraft has confirmed that the solar wind slows down much farther from the Sun than previously observed, with new data showing a 13%–15% deceleration at 58 AU. This slowdown, detailed in a recent study, happens as the solar wind interacts with interstellar neutral atoms, which are picked up and gradually drag on the flow of charged particles. These findings provide strong evidence for long-standing theories about the outer heliosphere and reveal how the solar wind changes as it moves toward the edge of our solar system and meets the interstellar medium.