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FireIcon.svg This English term is a hot word. Its inclusion on Wiktionary is provisional.


syn- (together) +‎ Hestia.



synestia (plural synestias)

  1. (astrophysics) A donut-shaped body of vaporized and molten rock formed from the collision of two planet-sized objects.
    • 2017 May 23, SJ Lock, ST Stewart, “The structure of terrestrial bodies: Impact heating, corotation limits, and synestias”, in Journal of Geophysical Research:
      For any rotating planetary body, there is a thermal limit beyond which the rotational velocity at the equator intersects the Keplerian orbital velocity. Beyond this corotation limit (CoRoL), a hot planetary body forms a structure, which we name a synestia, with a corotating inner region connected to a disk-like outer region.
    • 2017 June 3, Shannon Hall, “Early Earth was a molten doughnut”, in New Scientist, volume 234, number 3128, page 10:
      For a brief time during its infancy, Earth was a hot, doughnut-shaped blob called a synestia. [] A synestia has an exterior region marked by clouds of molten rock and dust, all at a scorching 2000°C or hotter.