Hubble detects water vapor in the atmosphere of a small exoplanet

The steamy world could be a sample of water-rich planets throughout our galaxy

The search for life in space goes hand in hand with the search for water on planets orbiting other stars. Water is one of the most common molecules in the universe, and all life on Earth requires it. Water acts 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 amazed when they find evidence of water vapor on exoplanets. The latest target is planet GJ 9827d, which may have a water-rich atmosphere around it. The planet is only twice the diameter of Earth, and could be an example of potential water-rich worlds elsewhere in our galaxy. But don't plan to buy property on GJ 9827d. The planet is as hot Venusat 800 degrees F. This makes it a very steamy world.

This is an artist's rendering of exoplanet GJ 9827d, the smallest exoplanet with water vapor detected in its atmosphere. The planet could be an example of potential planets with water-rich atmospheres elsewhere in our galaxy. The planet, which is roughly twice Earth's diameter, orbits the red dwarf star GJ 9827. There are two inner planets in the system on the left. The background stars are drawn as they can be seen with the naked eye when looking back toward our Sun. The sun is too faint to see. The blue star at the top right is Regulus; The yellow star in the middle bottom is Denebola; The blue star at the bottom right is the spike. The constellation Leo is on the left, and the constellation Virgo is on the right. Both constellations are distorted from our Earth-bound view from a distance of 97 light-years. Image credit: NASA, ESA, Leah Hostak (STScI), Ralph Crawford (STScI)

The Hubble Space Telescope finds water vapor in the atmosphere of a small exoplanet

Astronomers using NASA's Hubble Space Telescope have observed the smallest exoplanet where water vapor has been detected in the atmosphere. GJ 9827d, with a diameter roughly twice that of Earth, could serve as an example of potential planets with water-rich atmospheres elsewhere in our galaxy.

“This will be the first time we can directly show through atmospheric detection that these planets with water-rich atmospheres can actually exist around other stars,” said team member Björn Beneke, from the Trottier Institute for Exoplanet Research at the University of Montreal. . “This is an important step toward determining the prevalence and diversity of atmospheres on rocky planets.”

“The presence of water on a planet this small is a historic discovery,” added co-principal researcher Laura Kreidberg of the Max Planck Institute for Astronomy in Heidelberg, Germany. “It comes closer than ever to characterizing truly Earth-like worlds.”

Study of the planet's atmosphere

However, it is still too early to know whether Hubble has measured a small amount of water vapor using spectroscopy in a puffy, hydrogen-rich atmosphere, or whether the planet's atmosphere consists mostly of water, which was left behind after the atmosphere evaporated. Primitive hydrogen/helium under stellar radiation. .

“Our observing program, led by principal investigator Ian Crosfield 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 actually looking for water vapor specifically. Both results will be exciting, whether Water vapor was dominant or little Classify “In an atmosphere dominated by hydrogen,” said the paper's lead author, Pierre-Alexis Roy of the Trottier Institute for Exoplanet Research at the University of Montreal.

“Until now, we have not been able to directly detect the atmosphere of such a small planet. “We are slowly getting into this system now,” Beinecke added. “At some point, as we study small planets, there has to be a transition where there is no more hydrogen.” “On these small worlds, they have an atmosphere similar to that of Venus (dominated by carbon dioxide).”

Since the planet is as hot as Venus, at 800 degrees Fahrenheit, it would certainly be an inhospitable and steamy world if the atmosphere consisted mostly of water vapor.

Implications and future research

At present, the team has two possibilities. One scenario is that the planet is still clinging to a hydrogen-rich, water-filled atmosphere, making it a young planet.Neptune. Alternatively, it can be a warmer version of JupiterEuropa, which contains twice as much water as Earth under its crust. “Planet GJ 9827d could be half water and half rock. There will be a lot of water vapor on top of a smaller rocky body,” Beinecke said.

If the planet has a residual water-rich atmosphere, it must have formed far from its host star, where the temperature is cold and water is available in the form of ice, compared to its current location. In this scenario, the planet would have migrated closer to the star and receive more radiation. The hydrogen has been heated and escaped, or is still in the process of escaping the planet's weak gravity. An 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 — which were spaced over three years. During the transit, starlight is filtered through the planet's atmosphere and has the spectral signature of water molecules. If there are clouds on the planet, they are low enough in the atmosphere that they do not completely obscure Hubble's view of the atmosphere, and Hubble can probe the water vapor above the clouds.

“Observing water is a gateway to finding other things,” said Thomas Green, an astrophysicist at the University of California, California. NASAAmes Research Center in Silicon Valley, California. “This Hubble discovery opens the door for future study of these types of planets with the James Webb Space Telescope. With additional infrared observations, the James Webb Space Telescope can see much more, including carbon-bearing molecules such as carbon monoxide, carbon dioxide and methane. Once we have a total 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 its 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 Waterworld filter GJ 9827d” by Pierre-Alexis Roy, Björn Beneke, Caroline Piollet, Michael A. Julie Santiago, Ian JM Crosfield, Caroline V. Morley, Laura Krydberg, Thomas Michal Evans, Jonathan Brand, Simon DeLisle, Thomas B. Green, Kevin K. Hardegree-Ullman, Travis Barman, Jesse L. Christiansen, Diana Dragomir, Jonathan J. Fortney, Andrew W. Howard, Molly R. Kozirek, and Joshua D. Lothringer, September 12, 2023, the Astrophysical Journal Letters.
doi: 10.3847/2041-8213/acebf0

the Hubble Space Telescope It is an international cooperation project between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Maryland, operates the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts science operations on Hubble and Webb. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, DC