NASA’s Hubble Telescope Detects Water Vapour On Earth-Sized Exoplanet

In a groundbreaking discovery, astronomers using NASA’s Hubble Space Telescope have identified water vapour on the smallest exoplanet ever observed. GJ 9827d, with a diameter roughly twice that of Earth, may hold clues about the prevalence of water-rich atmospheres on planets beyond our solar system.

Water, as a fundamental component of life as we know it, plays a pivotal role in the quest for habitable exoplanets. The detection of water vapour on GJ 9827d represents a significant milestone in the study of rocky planets with potential Earth-like characteristics.

“This would be the first time that we can directly show through atmospheric detection, that these planets with water-rich atmospheres can actually exist around other stars,” Björn Benneke, a team member at the Trottier Institute for Research on Exoplanets at Université de Montréal, remarked in an official statement.

Co-principal investigator Laura Kreidberg of the Max Planck Institute for Astronomy in Heidelberg, Germany, expressed excitement over the discovery, stating, “Water on a planet this small is a landmark discovery. It pushes closer than ever to characterising truly Earth-like worlds.”

However, the nature of GJ 9827d’s atmosphere remains a mystery. Scientists are uncertain whether the observed water vapor is part of a hydrogen-rich atmosphere or if the planet’s atmosphere is primarily composed of water, left behind after the evaporation of a primeval hydrogen/helium atmosphere.

The planet’s scorching temperature, comparable to Venus at 800 degrees Fahrenheit, would make it an inhospitable, steamy world if the atmosphere were predominantly water vapour. The team is considering two possibilities – GJ 9827d may still retain a hydrogen-rich atmosphere laced with water, resembling a mini-Neptune, or it could be a warmer version of Jupiter’s moon Europa, potentially with half water and half rock.

The observations, conducted during 11 transits over three years, allowed scientists to analyse the planet’s atmosphere as it crossed in front of its host star. The data revealed the spectral fingerprint of water molecules, providing essential insights into the composition of GJ 9827d’s atmosphere.

Thomas Greene, an astrophysicist at NASA’s Ames Research Center, emphasised the significance of this discovery, stating, “Observing water is a gateway to finding other things.” He anticipates that the James Webb Space Telescope will play a crucial role in future studies of such planets, enabling a more comprehensive analysis of elements in their atmospheres.

GJ 9827d was initially discovered by NASA’s Kepler Space Telescope in 2017, completing an orbit around a red dwarf star every 6.2 days. Situated 97 light-years away in the constellation Pisces, this exoplanet opens new avenues for exploring the diversity of atmospheres on rocky planets beyond our solar system. The Hubble Space Telescope’s international collaboration between NASA and ESA, managed by NASA’s Goddard Space Flight Center, has once again expanded the understanding of the cosmos.