Definition

1. Noun:
   • The boundary marking the edge of the sun's influence: The heliopause is the theoretical boundary in space where the sun's solar wind is stopped by the interstellar medium.
   • The boundary between the interplanetary medium and the interstellar medium: It is the outer limit of the heliosphere, the region of space dominated by the sun's magnetic field and solar wind.

Usage Examples

• Noun:
  • The Voyager 1 spacecraft is believed to have crossed the heliopause in 2012.
  • Scientists study the heliopause to understand the interaction between our solar system and interstellar space.

Advanced Usage

• "to cross the heliopause": to pass beyond the boundary of the sun's dominant influence.
  • The probe's mission was to cross the heliopause and collect data from the interstellar medium.

Variants and Related Words

• Heliosphere (n): The vast, bubble-like region of space dominated by the sun's solar wind and magnetic field, extending outward to the heliopause.
  • The heliosphere protects the solar system from some cosmic rays.
• Termination shock (n): The inner boundary where the solar wind slows down abruptly before reaching the heliopause.
  • The spacecraft passed through the termination shock before reaching the heliopause.

Synonyms

• Heliospheric boundary: A technical synonym for the heliopause.
• Solar wind boundary: A descriptive term for the limit of the sun's solar wind.

Notes on Meaning

The heliopause is not a sharp, solid boundary but a vast, turbulent transition zone. Its exact location fluctuates based on the sun's activity and the pressure of the local interstellar medium. It represents the outermost edge of the sun's significant influence.

Noun

1. the boundary marking the edge of the sun's influence; the boundary (roughly 100 AU from the sun) between the interplanetary medium and the interstellar medium; where the solar wind from the sun and the radiation from other stars meet