Astronomers have finally managed to see behind the clouds the exoplanet GJ 1214b, a “mini-Neptune” planet orbiting a star about 40 light-years away, Live Science reports, citing Agerpres.

Mini-Neptune planets, a scaled-down version of the Solar System’s gas giant, are a common type of planet in our galaxy, but since there aren’t any in our Solar System, these worlds mostly remain interesting to scientists.

Previous observations of the distant planet have been hampered by thick layers of clouds, but the infrared thermal imaging instrument on the James Webb Space Telescope (JWST) has allowed astronomers to see behind them.

The results, published May 10 in the science journal Nature, show that GJ 1214b’s atmosphere consists of vapor, suggesting that the planet may have been a “water world” in its past, according to NASA researchers.

“For nearly a decade, the only thing we really knew about this planet was that it had a cloudy or hazy atmosphere,” Rob Zellem, an exoplanet researcher at NASA’s Jet Propulsion Laboratory, was quoted as saying in the report.

The temperature on the planet changed dramatically from day to night

The team used JWST’s Mid-Infrared Instrument (MIRI) to analyze the planet’s temperature as it orbited, gathering information from its day and night regions, allowing astronomers to learn what it’s made of.

Temperatures on GJ 1214b varied dramatically from day to night, reaching 280 degrees Celsius before cooling to over 37 degrees Celsius at night. Such a huge temperature difference indicates that the planet’s atmosphere cannot consist only of light hydrogen molecules. Instead, there must be something else, like water or methane.

Researchers consider this discovery an interesting clue about the planet’s past, since its atmosphere does not match the composition.

GJ 1214b “either lost a lot of hydrogen — if it started with a hydrogen-rich atmosphere — or formed from heavier elements from the start — more icy, water-rich material,” said study lead author Eliza Kempton, an astronomer at the University of Maryland. “The simplest explanation for a very water-rich planet is that it formed further away from the host star,” she added.

Astronomers still have a lot to learn about GJ 1214b, but they hope to observe more “mini-Neptune” planets with JWST in the near future.

According to Kempton, astronomers hope to uncover a “coherent story” about how the “mini-Neptune” planets formed and the circumstances under which they turned out to have so much water.