These visuals feature artist impressions.

Habitable Zone

The Habitable Zone is the region around a star where the conditions could potentially be suitable to sustain life on a planet within this region, for example allowing the presence of liquid water on its surface.

Often called the ‘Goldilocks Zone’, the Habitable Zone is a hypothetical region around a star where the conditions are just right to be considered potentially habitable. In that region, a planet’s surface temperature could be in the range needed to harbour liquid water on its surface. The energy from the star, together with the greenhouse effect generated by the planet’s atmosphere, would produce a surface temperature between 0 and 100℃.

Hubble’s observations have shown us that planets are being formed around many more stars than previously thought, increasing the possibility that life could exist somewhere out there. In future, Hubble could possibly find hints of life by studying exoplanet atmospheres. The chemical makeup of a planet’s atmosphere leaves a unique fingerprint on the starlight that passes through it, which Hubble can study.

In 2018, an international team of astronomers used Hubble to look for atmospheres around planets orbiting within or near the habitable zone of the ultracool dwarf star TRAPPIST-1, 40 light-years away. Of the seven Earth-sized planets that orbit TRAPPIST-1, three of them orbit within the system’s habitable zone.

In 2019, in an exciting discovery, Hubble data were used to detect water vapour in the atmosphere of a Super Earth within the habitable zone of its host star. K2-18b is eight times the mass of Earth and at its discovery was the only exoplanet known to have both water and temperatures that could support life.