heliopause

American  

[hee-lee-uh-pawz] / ˈhi li əˌpɔz /

noun

Astronomy.

1. the boundary of the heliosphere.

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heliopause British  

/ ˈhiːlɪəʊˌpɔːz /

noun

1. the boundary between the region of space dominated by the solar wind and the interstellar medium

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heliopause Scientific  

/ hē′lē-ə-pôz′ /

1. The region surrounding the solar system at which pressure from the outgoing solar wind equals the pressure from the interstellar medium (made up mostly of hydrogen and helium), and the solar wind can penetrate no further. It is considered to be the outer boundary of our solar system.

2. See more at solar wind

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Etymology

Origin of heliopause

First recorded in 1970–75; helio- + pause

Explanation

In astronomy, the heliopause is the outside edge or boundary of the heliosphere, the part of our solar system that's influenced by the sun. In 2012, NASA's Voyager 1 space probe crossed the heliopause. Astronomers have various theories about what happens beyond the heliopause, at such a far distance from the sun that solar wind doesn't affect anything. Inside the heliopause is the heliosphere, and everything outside of the heliopause is considered interstellar space. The word heliopause is rooted in the Greek word for "sun," helios, and the Latin pausa, "a halt, stop, or cessation."

Example Sentences

In 2012, Voyager 1 became the first human-made object to pass the heliopause frontier, where the fierce solar wind of subatomic particles yields to the force of other suns.

From New York Times • Jun. 14, 2024

The solar wind would run farther before sputtering to a stop at the heliopause, where the hot, wispy plasma of our heliosphere gives way to the cold, dense plasma of interstellar space.

From Science Magazine • Jul. 27, 2022

Both probes have, in the past decade, entered “interstellar space” after breaching the heliopause.

From Washington Times • Jun. 21, 2022

“But we did achieve something really amazing. It could have been that we never got to the heliopause, but we did.”

From Scientific American • Jun. 16, 2022

That place, called the heliopause, is one definition of the outer boundary of the Empire of the Sun.

From "Cosmos" by Carl Sagan