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Using Hubble, astronomers have detected water vapor in the atmosphere of GJ 9827d, a small exoplanet, suggesting the presence of water-rich atmospheres on similar planets. This discovery marks a significant step in the exploration of the composition and evolution of exoplanetary atmospheres. credit: SciTechDaily.com
Steamy World could be a showcase of water-rich planets across our galaxy
The search for life in space goes hand in hand with the search for water on planets around other stars. Water is one of the most common molecules in the universe and all life on Earth requires it. Water functions as a solvent by dissolving substances and enabling key chemical reactions in animal, plant and microbial cells. It is much better at this than other liquids.
Astronomers are intrigued to find evidence of water vapor on exoplanets. A recent target is the planet GJ 9827d, which may have a water-rich atmosphere around it. The planet, which is no more than twice the diameter of Earth, could be an example of possible water-rich worlds in other parts of our galaxy. But don’t plan to buy real estate in GJ 9827d. The planet is as hot as Venusat 800 degrees Fahrenheit. This makes it a torrid world.
This is an artist’s concept of exoplanet GJ 9827d, the smallest exoplanet where water vapor has been detected in the atmosphere. The planet could be an example of potential planets with water-rich atmospheres elsewhere in our galaxy. Only about twice the diameter of Earth, the planet orbits the red dwarf star GJ 9827. To the left are the system’s two inner planets. The stars in the background are represented as they would appear to the naked eye looking toward our Sun. The Sun is too faint to be seen. The blue star in the upper right corner is Regulus; the yellow star in the lower center is Denebola; and the blue star at the bottom right is Spica. The constellation Leo is on the left and Virgo is on the right. Both constellations are distorted from our view from Earth from 97 light years away. Credit: NASA, ESA, Leah Hustak (STScI), Ralf Crawford (STScI)
Hubble Space Telescope Finds Water Vapor in the Atmosphere of a Small Exoplanet
Astronomers using NASA’s Hubble Space Telescope observed the smallest exoplanet where water vapor has been detected in the atmosphere. At only about twice the diameter of Earth, planet GJ 9827d could be an example of potential planets with water-rich atmospheres elsewhere in our galaxy.
“This would be the first time that we can directly demonstrate, through an atmospheric detection, that these planets with water-rich atmospheres can actually exist around other stars,” said team member Björn Benneke of the Trottier Institute for Exoplanet Research. from the University of Montreal. . “This is an important step in determining the prevalence and diversity of atmospheres on rocky planets.”
“Water on such a small planet is a historic discovery,” added co-principal investigator Laura Kreidberg of the Max Planck Institute for Astronomy in Heidelberg, Germany. “It comes closer than ever to characterizing truly Earth-like worlds.”
Investigating the planet’s atmosphere
However, it remains too early to say whether Hubble spectroscopically measured a small amount of water vapor in a swollen, hydrogen-rich atmosphere, or whether the planet’s atmosphere is composed primarily of water, left over after a primitive atmosphere of hydrogen/helium will evaporate under stellar radiation. .
“Our observing program, led by principal investigator Ian Crossfield of the University of Kansas in Lawrence, Kansas, was specifically designed with the goal of not only detecting molecules in the planet’s atmosphere, but also specifically looking for water vapor. Either result would be interesting, whether water vapor is dominant or just a small amount. species in an atmosphere where hydrogen predominates,” said the lead author of the scientific paper, Pierre-Alexis Roy, of the Trottier Institute for Exoplanet Research at the University of Montreal.
“Until now we had not been able to directly detect the atmosphere of such a small planet. And little by little we are incorporating ourselves into this regime,” Benneke added. “At some point, as we study smaller planets, there should be a transition where there is no more hydrogen on these small worlds and they have atmospheres more like those of Venus (which is dominated by carbon dioxide).”
Because the planet is as hot as Venus, at 800 degrees Fahrenheit, it would definitely be a smoky, inhospitable world if the atmosphere was predominantly water vapor.
Implications and future research
At the moment the team is left with two possibilities. One scenario is that the planet is still clinging to a hydrogen-rich atmosphere mixed with water, making it a mini-Neptune. Alternatively, it could be a warmer version of JupiterEuropa’s moon Europa, which has twice as much water as Earth beneath its crust. “The planet GJ 9827d could be half water, half rock. And there would be a lot of water vapor on top of some smaller rock body,” Benneke said.
If the planet has a residual water-rich atmosphere, then it must have formed further from its host star, where the temperature is cold and water is available as ice, than its current location. In this scenario, the planet would have migrated closer to the star and received more radiation. The hydrogen heated up and escaped, or is still in the process of escaping, from the planet’s weak gravity. The alternative theory is that the planet formed near the hot star, with a trace of water in its atmosphere.
The Hubble program observed the planet during 11 transits (events in which the planet crossed in front of its star) that were spaced over three years. During transits, starlight filters through the planet’s atmosphere and bears the spectral signature of water molecules. If there are clouds on the planet, they are low enough in the atmosphere that they don’t completely obscure Hubble’s view of the atmosphere, and Hubble can probe water vapor above the clouds.
“Looking at water is a gateway to finding other things,” said Thomas Greene, an astrophysicist at POT‘s Ames Research Center in California’s Silicon Valley. “This Hubble discovery opens the door to future studies of this type of planets using the James Webb Space Telescope. JWST can see much more with additional infrared observations, including carbon-containing molecules such as carbon monoxide, carbon dioxide and methane. “Once we get a full inventory of a planet’s elements, we can compare them to the star it orbits and understand how it formed.”
GJ 9827d was discovered by NASA’s Kepler space telescope in 2017. It completes an orbit around a red dwarf star every 6.2 days. The star, GJ 9827, is located 97 light years from Earth in the constellation Pisces.
Reference: “Water absorption in the transmission spectrum of the candidate Water World GJ 9827 d” by Pierre-Alexis Roy, Björn Benneke, Caroline Piaulet, Michael A. Gully-Santiago, Ian JM Crossfield, Caroline V. Morley, Laura Kreidberg, Thomas Mikal-Evans, Jonathan Brande, Simon Delisle, Thomas P. Greene, Kevin K. Hartitle-Ullman, Travis Barman, Jessie L. Christiansen, Diana Dragomir, Jonathan J. Fortney, Andrew W. Howard, Molly R. Kosiarek, and Joshua D Lothringer, September 12, 2023, He Letters from astrophysical journals.
DOI: 10.3847/2041-8213/acebf0
He Hubble space telescope It is an international cooperation project between NASA and ESA. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble and Webb science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, DC