Hubble Finds Water Vapor on Scorching Super-Earth GJ 9827d
October 2, 2025
NASA's Hubble Telescope has detected water vapor in the atmosphere of a scorching super-Earth, GJ 9827d, marking a first for such a small exoplanet.
In a landmark discovery, NASA's Hubble Space Telescope has detected the signature of water vapor in the atmosphere of a scorching-hot super-Earth, GJ 9827d. Located 97 light-years away, this exoplanet is now the smallest planet outside our solar system where water has been conclusively identified, offering a crucial stepping stone in the quest to understand the atmospheric composition of distant rocky worlds.
A Steamy and Uninhabitable World
While the presence of water is exciting, GJ 9827d is far from a paradise. With a temperature soaring to approximately 800 degrees Fahrenheit (425 degrees Celsius), it's as hot as Venus, making it impossible for liquid water to exist on its surface. The planet is about twice Earth's diameter and orbits its red dwarf star in just 6.2 days. This discovery presents scientists with two intriguing possibilities for the planet's origin and composition.
- A Water-Rich World: GJ 9827d could be a 'mini-Neptune' that formed farther from its star, retaining a thick, water-rich atmosphere even as some of its primordial hydrogen and helium envelope was stripped away by stellar radiation.
- A Volcanic Steam World: Alternatively, it could be a warmer version of Jupiter's moon Europa, a rocky world with a significant steam atmosphere generated by ongoing volcanic activity, constantly replenishing the water vapor.
This discovery opens the door to studying the atmospheres of smaller, rockier planets in greater detail than ever before. It's a critical piece of the puzzle as we move toward identifying potentially habitable worlds with future instruments.
Pioneering the Search for Habitable Worlds
Hubble's observation, which involved analyzing 11 transits of the planet over three years, demonstrates our capacity to probe the environments of smaller exoplanets. While GJ 9827d itself is not habitable, it serves as an excellent target for future telescopes like the James Webb Space Telescope (JWST), which can analyze its atmosphere with even greater precision to determine its full composition. This finding is a testament to Hubble's enduring power and a promising glimpse into the future of exoplanet exploration.
Hubble Finds Water Vapor on Scorching Super-Earth GJ 9827d - FAQs
GJ 9827d is an exoplanet about twice Earth's mass located 97 light-years away. It has an incredibly high surface temperature of around 800°F (425°C).
It's the smallest exoplanet where water vapor has been detected, proving that even smaller, rocky worlds can have atmospheres with water, a key ingredient for life.
Hubble used transit spectroscopy, analyzing the starlight that passed through the planet's atmosphere. The unique chemical signature of water molecules was identified in the light spectrum.
Not necessarily. With a surface temperature of 800°F (425°C), GJ 9827d is far too hot for liquid water to exist and is not considered habitable.