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GJ 1214

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description GJ 1214 Overview

GJ 1214 is a faint M-type red-dwarf star in the constellation Ophiuchus, about 40 light-years from Earth. It is the host star of GJ 1214 b, a transiting planet announced in 2009 whose size and mass place it between Earth and the ice giants of the Solar System. Early models suggested a water-rich interior, and later observations have focused on its thick, difficult-to-characterize atmosphere, making the system a target for exoplanet and atmospheric research.

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What is GJ 1214 b?

GJ 1214 b is a Neptune-like exoplanet orbiting the M-type red dwarf GJ 1214 in Ophiuchus, roughly 40 light-years away. NASA lists its mass as about 8.17 Earth masses and its orbital period as about 1.6 days. [NASA Exoplanet Catalog](https://science.nasa.gov/exoplanet-catalog/gj-1214-b/)

When was GJ 1214 b discovered?

The MEarth project announced GJ 1214 b in 2009, and the HARPS spectrograph at ESO's 3.6-meter telescope helped measure its mass. Its transit across the star made both its size and mass unusually accessible for an early super-Earth study. [NASA Science](https://science.nasa.gov/resource/gj1214b/)

Why was GJ 1214 b once called a possible water world?

Early mass and radius models allowed an interior rich in water ice, leading to the popular water-world description. Later observations have emphasized the difficulty of reading its atmosphere because high-altitude clouds or hazes can hide the underlying composition.

How do astronomers study GJ 1214 b if it is so far away?

They measure the planet's transit, the slight dip in starlight when it crosses GJ 1214, and combine that with radial-velocity measurements of the host star. The planet's short 1.6-day orbit allows repeated observations. [NASA Exoplanet Catalog](https://science.nasa.gov/exoplanet-catalog/gj-1214-b/)

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