Water vapor has been detected in the atmosphere of an exoplanet the size of Neptune about 150 light years from Earth. The research, which was presented by astronomers at the University of Kansas, is an important finding in the realm of space exploration.
The exoplanet discovered is a gas giant orbiting close to its star, which means it is not considered a habitable place that could support alien life.
But the scientists say their findings show how studying the chemical makeup of exoplanet atmospheres can help astronomers learn how they formed and how they compare to planets closer to our home, Earth.
"This planet is a little bigger than Neptune, but very, very different," said Jonathan Brande, a doctoral student in physics and astronomy at the University of Kansas, who led the research.
"So the question is: How did this planet form and get to where it is now, and how did Neptune in our Solar System form and get to where it is now?" he added.
The exoplanet, known as TOI-674 b, is about 1.3 times the size of Neptune, but orbits much more tightly, taking less than two days to circle its parent star.
This is not the first time water vapor has been found in the atmosphere of an exoplanet. In 2019, the Hubble Space Telescope discovered water vapor on a distant planet known as K2-18b, which is in the "habitable zone" of its parent star, where conditions are such that liquid water can exist on the planet's surface.
But Brande said it was unusual to see a Neptune-sized planet with a detectable atmosphere so close to its parent star, which may indicate that the exoplanet was born farther away before migrating to its current position.
This research has not been published in a peer-reviewed journal. Brande said the findings had been submitted to The Astronomical Journal.
Scientists study exoplanets by observing them as they pass in front of, or transit through, their parent star. Measuring the spectrum of light shining through an exoplanet's atmosphere during transit can reveal the presence of water vapor or other chemical signatures, such as methane or carbon dioxide.
In this case, the TOI-674 b's size makes it an ideal target. Each time an exoplanet passes in front of its star, it blocks 1.3% of the star's light.
Brande and his colleagues observed the atmosphere of TOI-674 b using the Hubble Space Telescope instrument. They combined the observations with data from NASA's Transiting Exoplanet Survey Satellite, launched in 2018, and NASA's Spitzer Space Telescope, which was decommissioned last January after a 16-year mission.
To note, NASA's recently launched James Webb Space Telescope will be able to study exoplanet atmospheres in greater detail when it goes official online later this year.