Astronomers make unprecedented discovery of water vapor on exoplanet

Astronomers made an unprecedented discovery by detecting water vapor in the atmosphere of a small, extremely hot exoplanet (a celestial body that does not orbit around the sun) 97 light-years from Earth. The information was released by NASA on Thursday (25).

Using the Hubble Space Telescope, astronomers discovered that the planet, named GJ 9827d, is about twice the diameter of Earth and is the smallest exoplanet found with water vapor in its atmosphere.

Water is essential for life as we know it. However, the planet is unlikely to host any life due to scorching temperatures that would turn a water-rich atmosphere into scalding steam.

Astronomers have not yet discovered the true nature of the new world's atmosphere, but the revelation paves the way for further investigation as they seek to understand the origins of planets beyond our solar system.

The findings were reported in detail in a report published in The Astrophysical Journal Letters.

“Water on such a small planet is a landmark discovery,” study co-author Laura Kreidberg, managing director of the exoplanet atmospheric physics department at the Max Planck Institute for Astronomy in Heidelberg, Germany, said in a statement.

“This is closer than ever to characterizing truly Earth-like worlds,” he added.

“This would be the first time that we can directly show, through atmospheric detection, that these planets with water-rich atmospheres can actually exist around other stars,” said study co-author Björn Benneke, professor at the Trottier Institute of Exoplanet Research. “This is an important step towards determining the prevalence and diversity of atmospheres on rocky planets,” he added.

Currently, the research team cannot say whether Hubble captured traces of water vapor in a swollen, hydrogen-rich atmosphere or whether the planet has a water-rich atmosphere because the host star evaporated GJ 9827d's original hydrogen and helium atmosphere. .

“Our observation program, led by principal investigator Ian Crossfield (from the University of Kansas) in Kansas, United States, was specifically designed with the goal of not only detecting the molecules in the planet's atmosphere, but also specifically looking for water vapor ,” said the study’s lead author, Pierre-Alexis Roy, a doctoral student at the Trottier Institute at the University of Montreal, Canada, also in a statement.

“Either outcome would be exciting, whether water vapor is dominant or just a tiny species in a hydrogen-dominant atmosphere,” Roy added.

How the discovery worked

NASA's Kepler mission initially 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, or times when the planet passed in front of its star during orbit, over three years. Starlight filtered through the planet's atmosphere helped astronomers measure the signature of water molecules.

“Until now, we had not been able to directly detect the atmosphere of such a small planet. We are slowly entering this regime now,” Benneke said. “At some point, as we study smaller planets, there should be a transition where there will be no more hydrogen on these small worlds and they will have atmospheres more like Venus (which is dominated by carbon dioxide).”

Understanding more about the planet's atmosphere could help astronomers classify exactly what kind of world GJ 9827d is. Currently, the team has two possible theories.

It's possible the planet is a mini-Neptune with a hydrogen-rich atmosphere that contains water vapor. If so, GJ 9827d likely formed at a greater distance from the host star than its current location, meaning the planet was colder and water was present in the form of ice (similar to Neptune and Uranus, the planets furthest from our solar system).

As the planet migrated closer to its star and was hit by more stellar radiation, the hydrogen heated up and escaped, or is still escaping, according to the researchers.

The other theory astronomers suspect is that GJ 9827d could be a hotter version of Jupiter's icy moon Europa, which contains an ocean beneath a thick, icy crust. The planet could be half water and half rock, Benneke said.

The search for water in space

Water is one of the most common molecules found throughout the universe, and for years, astronomers have included detecting water as a larger part of the search for life beyond Earth.

“Looking at water is a gateway to finding other things,” said study co-author Thomas Greene, an astrophysicist at NASA Ames Research Center in Silicon Valley, California, United States, in a statement.

Astronomers have already observed GJ 9827d with the Webb telescope for water and other types of molecules, and this data will be shared in the future.

“We can’t wait to see what this data reveals,” said Kreidberg. “We hope that we can now resolve the issue of water worlds once and for all.”