NASA’s Hubble Telescope Discovers Water on Smallest Exoplanet Yet
In a groundbreaking discovery, NASA’s Hubble Space Telescope has detected the presence of water on the smallest exoplanet ever observed. The planet, known as GJ 9827D, was initially discovered in 2017 by NASA’s Kepler Space Telescope. Located approximately 97 light years away and roughly twice the diameter of Earth, this tiny exoplanet completes an orbit around its nearest star, a red dwarf, in just over six Earth days.
The recent discovery of water on GJ 9827D has been hailed as a “landmark discovery” by Laura Kreidberg, a researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany. Kreidberg, who is also a co-principal investigator in the study that unveiled this finding, believes that this brings astronomers closer than ever to characterizing truly Earth-like worlds.
The detection of water on GJ 9827D was made possible by the Hubble telescope, marking the first time that an exoplanet of this kind has been found to exist around other stars. By observing the planet during eleven transits over a period of three years, astronomers were able to analyze the light produced by its host star as it passed through the exoplanet’s atmosphere. This allowed them to identify key spectra that indicated the presence of water molecules.
Björn Benneke, an astronomer at the Trottier Institute for Research on Exoplanets at Université de Montréal, emphasized the significance of this discovery in determining the prevalence and diversity of atmospheres on rocky planets. He stated, “This is an important step toward determining the prevalence and diversity of atmospheres on rocky planets.”
However, the researchers are still uncertain about the exact nature of GJ 9827D’s atmosphere. It is unclear whether the planet is a “water world” with an abundance of liquid or if the presence of water vapor in its hydrogen-rich atmosphere is merely a small component. Pierre-Alexis Roy, lead author of the study, expressed excitement about both possibilities, stating that it would be intriguing to determine whether water vapor dominates or if it is just a minor species in a hydrogen-dominant atmosphere.
Despite possessing water like Earth, GJ 9827D’s close proximity to its star means that it resembles Venus more closely due to its extreme heat. With temperatures reaching up to 800 degrees Fahrenheit, it seems unlikely that this exoplanet could support life, especially if there is an abundance of water vapor in its atmosphere.
However, if GJ 9827D possesses an atmosphere rich in hydrogen and a certain degree of water vapor, it could potentially be classified as a mini-Neptune or even resemble Jupiter’s moon Europa, which is known to have approximately twice as much water as Earth. The researchers speculate that if there are equal parts water and rock on GJ 9827D, the water vapor may exist above the planet’s smaller rock body.
Additionally, the team suggests that the water-richness of GJ 9827D’s atmosphere could be residual if the planet initially formed farther away from its star. As the planet moved closer to its stellar host, the heating caused by increased radiation over time could have heated the water.
Thomas Greene, an astrophysicist at NASA’s Ames Research Center, sees the observation of water as a gateway to further discoveries. He believes that NASA’s upcoming James Webb Space Telescope will provide additional infrared observations that can reveal carbon-bearing molecules like carbon monoxide, carbon dioxide, and methane. By obtaining a complete inventory of a planet’s elements and comparing them to the star it orbits, scientists can gain insights into how the planet was formed.
The team’s new paper, titled “Water Absorption in the Transmission Spectrum of the Water World Candidate GJ 9827 d,” was published in The Astrophysical Journal Letters. This groundbreaking discovery opens up new possibilities for understanding the composition and potential habitability of exoplanets, bringing us one step closer to unraveling the mysteries of the universe.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on Twitter: @MicahHanks.