Mysterious planet has "unusually shiny atmosphere" and may contain water vapor, researchers say

A strange planet that's stymied astronomers for years has an "unusually shiny atmosphere" and could be home to large amounts of water vapor, scientists said in a study published Wednesday in the journal Nature.

The distant planet, which is outside of our solar system about 40 light-years away, is totally covered in a deep haze that has made it difficult to study since it was first discovered in late 2009, researchers said. Eliza Kempton, an associate professor of Astronomy at the University of Maryland and lead author of the study, said she's been trying to get a clearer picture of the planet for more than a decade. 

"Whatever is making up the hazes or clouds is not what we expected. It's bright, it's reflective and that's confusing and surprising," Kempton said, according to the University of Maryland. "This is going to point us toward a lot of further studies to try to understand what those hazes could be."

The James Webb Space Telescope recently helped to reveal new information about the planet, formally named GJ 1214b. Planets such as GJ 1214b are often referred to as mini-Neptune planets because they're smaller than Neptune but with a similar atmospheric makeup. According to NASA, they are the most common type of planet in the galaxy, although none exist in our solar system.

While studying GJ 1214b, researchers tracked the planet through nearly its entire orbit over the course of about 40 hours, according to NASA. The planet's year takes only 1.6 Earth days.

"The ability to get a full orbit was really critical to understand how the planet distributes heat from the day side to the night side," Kempton said in a NASA Jet Propulsion Laboratory post. "There's a lot of contrast between day and night.

The night side is, unsurprisingly, colder than the day side, with temperatures shifting from 535 to 326 degrees Fahrenheit.

Those temperatures are actually cooler than expected. The cooler temperatures are caused by what NASA described as an "unusually shiny atmosphere." The atmosphere reflects a large proportion of the light from its parent star instead of absorbing it and becoming hotter. 

The research also revealed that the planet could be a water world, meaning its atmosphere "likely contains water vapor—possibly even significant amounts," the University of Maryland said. But astronomers aren't sure yet if GJ 1214b is a water world because water vapor absorption and methane absorption can look similar in observations.

"This is not a primordial atmosphere," Kempton said, according to NASA. "It does not reflect the composition of the host star it formed around. Instead, it either lost a lot of hydrogen, if it started with a hydrogen-rich atmosphere, or it was formed from heavier elements to begin with – more icy, water-rich material."

Kempton's research suggests that GJ 1214b may have formed farther away from its star, then moved inward toward its current orbit. 

"The simplest explanation, if you find a very water-rich planet, is that it formed farther away from the host star," Kempton said.

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