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Deep Field
29 September 2026 2518 stories tracked

Glossary · Exoplanets & Life

Terminator zone

The permanent twilight ring on a tidally locked planet, and the only part that might be habitable.

A planet locked to its star has a scorched day side and a frozen night side, with a band of eternal dusk between them. If the planet has an atmosphere thick enough to move heat around, that ring is where temperatures could allow liquid water. It is the most likely habitable configuration around red dwarf stars, which are the most common stars there are — so the question of whether a terminator zone can hold a stable climate matters more than its strangeness suggests.

Related terms

Transit method Finding planets by watching a star dim slightly as one passes in front. Radial velocity Finding planets by the wobble they induce in their star's motion. Habitable zone The orbital band where a planet could hold liquid water — no more than that. Sub-Neptune The most common kind of planet in the galaxy, and there is not one in our solar system.

Questions

What is Terminator zone?

The permanent twilight ring on a tidally locked planet, and the only part that might be habitable.

Why does it matter?

If the planet has an atmosphere thick enough to move heat around, that ring is where temperatures could allow liquid water. It is the most likely habitable configuration around red dwarf stars, which are the most common stars there are — so the question of whether a terminator zone can hold a stable climate matters more than its strangeness suggests.

Written and computed by . Corrections and errors to hello@cantinalabs.dev.