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Astronomers using the Hubble Space Telescope have detected water molecules in the atmosphere of a small, very hot exoplanet 97 light-years from Earth.
The planet, called GJ 9827d, is about twice the diameter of Earth and is the smallest exoplanet with water vapor in its atmosphere, according to a new study.
Water is essential for life as we know it, but the planet is unlikely to host any kind of life due to scorching temperatures that would turn a water-rich atmosphere into scorching steam.
Astronomers have yet to uncover the true nature of this unusual Earth’s atmosphere, but this discovery paves the way for further research as we try to understand the origins of planets beyond our solar system.
The findings were revealed in a report published Thursday in The Astrophysical Journal Letters.
“Water on such a small planet is a landmark discovery,” Laura Kreidberg, general manager of the atmospheric physics department of exoplanets at the Max Planck Institute for Astronomy in Heidelberg, Germany, said in a statement. “It comes ever closer to characterizing truly Earth-like worlds.”
But the planet reaches temperatures of 800 degrees Fahrenheit (427 degrees Celsius), making it a steamy, inhospitable world as hot as Venus.
“This will be the first time we can directly demonstrate through an atmospheric detection that these planets with water-rich atmospheres can actually exist around other stars,” said Björn Benneke, a professor at the Trottier Research Institute at the University of Montreal. Exoplanets in a statement. “This is an important step towards determining the prevalence and diversity of atmospheres on rocky planets.”
At this time, the research team cannot say whether Hubble detected traces of water vapor in a puffy, hydrogen-rich atmosphere, or whether the planet has a water-rich atmosphere because its host star has evaporated GJ 9827d’s original hydrogen and helium atmosphere.
“Our observation program, led by principal investigator Ian Crossfield (University of Kansas) in Lawrence, Kansas, is specifically designed not only to detect molecules in the planet’s atmosphere, but also to look specifically for water vapor.” lead study author Pierre-Alexis Roy, a doctoral student at the Trottier Institute at the University of Montreal, said in a statement. “Whether it is dominated by water vapor or just a small species in an atmosphere dominated by hydrogen, both results would be exciting.”
A planetary riddle
NASA’s Kepler mission first discovered the planet orbiting a red dwarf star in the constellation Pisces in 2017. The exoplanet completes a single orbit around its host star every 6.2 days.
Astronomers observed GJ 9827d during 11 transits over three years, times when the planet passed in front of its star during its orbit. Starlight filtered through the planet’s atmosphere helped astronomers measure the signature of water molecules.
“Until now, we could not directly detect the atmosphere of such a small planet. “And now we are slowly entering this regime,” Benneke said. “At some point, as we study smaller planets, there has to be a transition where these smaller worlds no longer have hydrogen and have atmospheres more like Venus (dominated by carbon dioxide).”
Learning more about the planet’s atmosphere could help astronomers classify exactly what type of world GJ 9827d is. Currently the team has two possible theories.
It is possible that the planet is a mini-Neptune with a hydrogen-rich atmosphere containing water vapor. If so, GJ 9827d probably formed further from its host star than its current location; This means that the planet is colder and water is present in the form of ice (similar to Neptune and Uranus, the most distant planets in our solar system). .
As the planet moved closer to its star and was exposed to more stellar radiation, the hydrogen heated up and escaped, or is still escaping, according to the researchers.
Or, astronomers suspect, GJ 9827d may be a hotter version of Jupiter’s icy moon Europa, which contains an ocean beneath its thick, icy crust. Benneke said the planet may be half water and half rock.
Search for water in space
Water is one of the most common molecules found in the universe, and for years astronomers have considered its detection as part of the larger search for life beyond Earth.
“Observing water is a gateway to finding other things,” study co-author Thomas Greene, an astrophysicist at NASA’s Ames Research Center in California’s Silicon Valley, said in a statement. “This Hubble discovery opens the door to future study of such planets by the James Webb Space Telescope. JWST can see many more with additional infrared observations, including carbon-bearing molecules such as carbon monoxide, carbon dioxide and methane. Once we have a complete inventory of a planet’s elements, “We can compare them to the star they orbit and understand how they formed.”
Astronomers have already observed GJ 9827d with the Webb telescope to look for water and other types of molecules, and this data will be shared in the future.
“We can’t wait to see what these data will reveal,” Kreidberg said. “I hope we can now solve the problem of water worlds once and for all.”
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