Aprilean

Aprilean is a small, rocky exoplanet located in the habitable zone of the K-type star Gliese 221, approximately 45 light‑years from Earth. First detected in 2021 by the Transiting Exoplanet Survey Satellite (TESS), the planet has a radius 1.2 times that of Earth and a mass roughly 1.5 Earth masses, suggesting a rocky composition with a substantial iron core. Its orbital period around Gliese 221 is 40.6 Earth days, giving Aprilean a relatively short year and a surface temperature that averages around 22 °C (72 °F) under a thin atmosphere assumed to be dominated by nitrogen and carbon dioxide.

The name "Aprilean" derives from the Latin word *aprilior*, meaning "of April", in reference to the star's springlike position in the sky during Earth’s April and the planet’s discovery date. Astronomical surveys indicate that Aprilean may host a thin hydrosphere, though spectroscopic analysis of its atmosphere has not yet confirmed the presence of water vapor. The planet's rotational period is estimated to be 20.5 Earth hours, which would render its day length slightly shorter than Earth's.

Studying Aprilean provides insight into terrestrial planet formation around K-type stars, which are well known for their long lifespans and stable luminosities. Future missions, such as the James Webb Space Telescope and upcoming ground‑based observatories, aim to characterize its atmosphere and surface conditions in greater detail, potentially revealing whether the planet could sustain life as we understand it.