heliopause
Americannoun
noun
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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.
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See more at solar wind
Etymology
Origin of heliopause
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."
Vocabulary lists containing heliopause
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
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
Crossing the heliopause, Voyager 1 should have observed a change in the direction of the magnetic field, as the solar wind’s twisting field gives way to differently oriented interstellar fields.
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
Voyager 2 arrived when the solar wind was peaking, which, if the models were correct, should have pushed the heliopause farther out than 120 AU.
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
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
