Earth & SkyGreek → English
Periastron
/ˌpɛriˈæstrɒn/noun
The point in an orbit where a body comes closest to the star it circles.
The Greek roots
περί
perí
around, near
ἄστρον
ástron
star
Literally: “near the star”
The story of the word
Astronomers built the word on the pattern already set by perihelion, near the sun, and perigee, near the earth; the far end of the same orbit is apastron. Binary star work needed it first, because two stars circling each other have no sun to refer to. Exoplanet hunters now use it constantly, since a planet at periastron is hottest and easiest to detect.
- How it travelled
- Ancient Greek → scientific coinage → English
- First recorded
- 19th century
Same family
perihelionperigeeastronomyasteroiddisaster
In a sentence
The comet-like planet roasts at periastron and freezes at the other end of its orbit.
They timed the flare to within days of periastron passage.