The exoplanet HD 20794d swoops in and out of its habitable zone every few hundred days, making for an extreme climate.

Located less than 20 light years away, HD 20794d could potentially be one of the most Earth-like planets found so far, despite its extreme climatic variability.

An exoplanet is a planet outside our solar system that usually orbits a star in our galaxy. More than 7,000 have been found in the Milky Way since the first confirmed discovery in the 1990s, and "billions more remain to be discovered", said Tech Explorist.