Knowra K2-18b K2-18b K2-18b is a temperate sub-Neptune exoplanet orbiting the red dwarf K2-18 about 124 light-years from Earth. Its atmosphere has been studied for signs of molecules associated with habitability.
Transit photometry : A method that detects exoplanets by measuring periodic dimming as they pass in front of their stars. K2-18b was discovered through the small, repeating dips in its star’s brightness.
Sub-Neptune : An exoplanet larger than Earth but smaller than Neptune, with properties that vary widely. K2-18b belongs to this broad class, whose members need not resemble scaled-down Neptunes.
Dimethyl sulfide : A sulfur-containing molecule produced by marine organisms on Earth and also by nonbiological processes. A disputed possible detection in K2-18b’s atmosphere prompted claims about potential biological activity.
Super-Earth : An exoplanet more massive than Earth but smaller than Neptune, without a universally agreed composition boundary. K2-18b lies near the size-based distinction between super-Earths and sub-Neptunes.
Transmission spectroscopy : A technique that analyzes starlight filtered through a transiting planet’s atmosphere. It has been used to identify and constrain gases in K2-18b’s atmosphere.
Red dwarf : A small, cool, low-mass star that burns hydrogen slowly and emits mostly red light. K2-18b orbits a red dwarf, shaping its received radiation and transit opportunities.
Methane : A simple carbon-containing gas found in planetary atmospheres and produced by biological and geological processes. Observations of K2-18b have reported methane, a key ingredient in debates about its atmospheric chemistry.
Mini-Neptune : A small Neptune-like planet, often modeled with a deep atmosphere rich in hydrogen and helium. This interpretation competes with models in which K2-18b has a substantial water-rich interior.
James Webb Space Telescope : A space observatory designed for infrared astronomy, including studies of distant galaxies and exoplanet atmospheres. Its infrared observations made detailed studies of K2-18b’s atmosphere possible.
Habitable zone : The range of orbital distances where a planet could maintain liquid water on its surface under suitable conditions. K2-18b receives an amount of stellar energy that places it near its star’s habitable zone.
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