Artist's impression of the exoplanet. Image: NASA/ESA/Leah Hustak/Ralf Crawford
According to Prof Björn Benneke of the Université de Montréal, researchers have not been able to directly detect the atmosphere of such a small planet until now.
Hubble may no longer be the most powerful telescope in space, but it is still proving useful for astronomical research, such as in the latest discovery of water vapour in a distant exoplanet.
Astronomers using the Hubble Space Telescope have observed for the first time water vapour in the atmosphere of a distant exoplanet GJ 9827d that is so small, at about twice the Earth’s diameter, signalling that there may be many such planets out there.
While scientists are not sure if the water vapour is present only in traces in the planet’s atmosphere or if it is abundant, team member Dr Björn Benneke said this is the first time we have directly shown such planets can exist around other stars through atmospheric detection.
“This is an important step toward determining the prevalence and diversity of atmospheres on rocky planets,” said Benneke, who is associate professor and the head of the Astronomy Group in the Department of Physics at the Université de Montréal.
According to Benneke, researchers have not been able to directly detect the atmosphere of such a small planet until now.
“We’re slowly getting into this regime now,” he said. “At some point, as we study smaller planets, there must be a transition where there’s no more hydrogen on these small worlds, and they have atmospheres more like Venus (which is dominated by carbon dioxide).”
💧New water detection!💧
The NASA/ESA @HUBBLE_space telescope has detected water vapour in a small exoplanet's atmosphere.
At only approximately twice Earth’s diameter, the planet GJ 9827d could be an example of potential planets with water-rich atmospheres elsewhere in our… pic.twitter.com/FPxjuk1B7I
— ESA (@esa) January 25, 2024
The team predicts two possibilities based on initial findings: the water vapour is either only a small amount detected in a “puffy hydrogen-rich atmosphere” or pervasive – left behind after a “primaeval” hydrogen/helium atmosphere evaporated under stellar radiation.
“Our observing programme was designed specifically with the goal of not only detecting the molecules in the planet’s atmosphere, but of actually looking specifically for water vapour,” explained lead author of a paper on the study, PhD researcher Pierre-Alexis Roy of the Université de Montréal.
“Either result would be exciting, whether water vapour is dominant or just a tiny species in a hydrogen-dominant atmosphere.”
This is not the first time water vapour has been detected on an exoplanet.
In November, Prof Tom Ray of the Dublin Institute for Advanced Studies was part of a team that looked deeply into the cloud-covered atmosphere of WASP-107b, a gaseous exoplanet orbiting a star slightly cooler and smaller than the sun.
Observations from the James Webb, specifically from its mid-infrared instrument, allowed them to unravel the chemical composition of its atmosphere, which they found to include water vapour, sulphur dioxide and silicate sand clouds.
Earlier, scientists from Europe and North America were able to use data from the James Webb to discover methane and carbon dioxide in the atmosphere of K2-18 b, a distant exoplanet that has long piqued the curiosity of astronomers for having the potential to sustain life.
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