Earth & SkyGreek → English
Heliosphere
/ˈhiːlioʊsfɪər/noun
The bubble of space carved out around the sun by the solar wind.
The Greek roots
ἥλιος
hḗlios
sun
σφαῖρα
sphaîra
ball, globe
Literally: “sun sphere”
The story of the word
Coined in the 1960s for a region nobody had reached and nobody could measure, once physicists worked out that the solar wind must blow a cavity in the interstellar gas. It is not spherical: the sun's motion through the galaxy drags it out into a long tail. Voyager 1 crossed the outer boundary in 2012, about 18 billion kilometres out.
- How it travelled
- Ancient Greek → scientific coinage → English
- First recorded
- 1960s
Same family
heliumheliotropeperihelionheliopause
In a sentence
Cosmic rays from outside are partly shielded by the heliosphere.