Insolation
In Astronomy the term insolation refers to the amount of light, from Sol, our sun, that shines on Solar system objects, like planets, comets and asteroids.
The term instellation is used to refer to the amount of light falling on exoplanets and other objects that orbit other stars.[1][2][3]
References
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Evan Gough (2026-01-14). "Two New Exoplanets And The Need For New Habitable Zone Definitions". Universe Today. Archived from the original on May 10, 2026. Retrieved 2026-06-24.
An exoplanet's instellation flux, or insolation flux, describes the amount of solar energy that reaches the exoplanet's surface. It's measured in watts per square meter (W/m²). In the paper, the expression 0.1 < 𝑆/S⊕ < 5 defines a range of insolation flux relative to Earth's solar constant. So it translates to a range between about 136 W/m² and about 6805 W/m². Earth's solar constant is around 1361 W/m² at the top of the atmosphere, so that gives an idea of what the term is describing.
- ↑
Lewis Dartnell (2025-11-08). "Bare, hostile alien worlds may be able to host life after all, after astronomers made one key change". BBC Sky at Night Magazine. Archived from the original on 2025-12-17. Retrieved 2026-06-24.
In an influential 2017 paper, Kevin Zahnle and David Catling plotted known exoplanets, as well as the planets and moons in our Solar System, on axes of escape velocity versus instellation.
- ↑ Keith Cowing (2025-04-28). "Near-circular orbits for planets with Earth-like sizes and instellations around M and K dwarf stars - Nature Astronomy". Nature magazine. Retrieved 2026-06-24.