Discovery of GJ 357 d by NASA’s TESS on July 31, 2019

On July 31, 2019, NASA’s Transiting Exoplanet Survey Satellite (TESS) made headlines with the discovery of its first potentially habitable Earth-sized planet located within the habitable zone of its star. The exoplanet was named GJ 357 d, and its finding represented a significant milestone in the ongoing search for extraterrestrial life.

Background on TESS

Launched in April 2018, TESS is designed to survey the sky to identify transiting exoplanets. It monitors the brightness of stars, searching for periodic drops caused by planets passing in front of them, an event known as a transit. TESS aims to discover small planets around the brightest stars near the Earth, greatly enhancing our understanding of planetary systems beyond our Solar System.

Details of the Discovery

GJ 357 d orbits a star called GJ 357, a member of the Hydra constellation. Located approximately 31 light-years from the Sun, this M-type dwarf star is smaller and cooler than our own star, providing a unique environment potentially favorable for life.

Key specifications of GJ 357 d include:

• Size and Composition: It is roughly twice the size of Earth and is classified as a super-Earth, suggesting a mix of rocky and gaseous components.
• Orbit: GJ 357 d orbits its star every 55.7 days.
• Temperature and Habitability: Although its exact surface temperature is uncertain, models indicate it could be conducive to maintaining liquid water, depending on atmospheric conditions.

Significance and Implications

The discovery of GJ 357 d is particularly noteworthy due to its presence in the star’s habitable zone, which is the range of distances where conditions might be right for liquid water to exist on a planet’s surface—an essential criterion for life as we know it.

The identification of such exoplanets is crucial not only for understanding the variety of planetary systems but also for selecting potential candidates for future, more detailed observations. These observations could determine atmospheric characteristics and search for biosignatures or other indicators of life.

Conclusion

The finding of GJ 357 d underscores the importance and success of TESS in the exoplanetary exploration frontier. As our methods and technologies evolve, discoveries like this one inch humanity closer to answering the profound question of whether life exists beyond Earth.