- GJ 1214 b is a distant planet, about 48 light-years from Earth. Astronomers thought it was probably a watery and rocky world larger than Earth, or a smaller version of our solar system’s ice giant Neptune. They gave it a name meaning “large body of water.”
- But now it seems this world might be an oversized Venus, researchers in Japan and the U.S. said this month. New results from NASA’s Webb Space Telescope suggest its atmosphere is like that of Venus, mostly carbon dioxide.
- If so, it’s a new class of planet, unlike any seen before.
In 2009, when astronomers discovered the exoplanet known as GJ 1214 b, they thought it was likely either a super-Earth water world or a mini-Neptune. Those are two of the different kinds of exoplanets discovered so far in our home galaxy, the Milky Way. But a blanket of haze in the atmosphere of GJ 1214 b made classification difficult. And now, it appears, they were wrong.
Now, a new study suggests, GJ 1214 b is entirely new to astronomers’ understanding of the worlds inhabiting our Milky Way. Using NASA’s Webb space telescope, researchers at the National Astronomical Observatory of Japan and the University of Arizona in the U.S., said in two press releases (January 15, 2025, and January 24) that the planet is probably more like an oversized Venus, with a thick atmosphere of carbon dioxide. So it’s a super-Venus.
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The research teams published their peer-reviewed findings in two new papers in The Astrophysical Journal Letters, on October 16, 2024 and January 14, 2025.
New Release: Super-Earth vs. Sub-Neptune? The Winner is Super-Venus!
New observational data from the James Webb Space Telescope and simulation models have confirmed a new type of planet unlike anything found in the Solar System. pic.twitter.com/QArSzwcUcC— NAOJ (@prcnaoj_en) January 15, 2025
GJ 1214 b, aka Enaiposha
Astronomers first found GJ 1214 b in 2009, orbiting a star 48 light-years away in the direction to our constellation Ophiuchus. Scientists thought it was most likely a super-Earth – larger and more massive than Earth – with a water-rich atmosphere and possible global ocean. It’s an interesting place, which is why, in 2023, the International Astronomical Union (IAU) included this world in a public exoplanet-naming process. That process resulted in the official name Enaiposha for GJ 1214 b. The name means “large body of water” in the Maasai language.
The IAU also acknowledged that GJ 1214 b might instead be a mini-Neptune, an ice giant with a deep hydrogen atmosphere. Or it might be a rocky planet like Earth, but with a hydrogen atmosphere. They weren’t sure!
What did we know for sure as recently as 2023? We knew that the planet orbits its star about 70 times closer than Earth orbits our sun. But, beyond that, GJ 1214 b or Enaiposha was mysterious. As Matthew Murphy, a graduate student at the University of Arizona and co-author of both papers said:
It has been the prevailing puzzle in the field for a decade.
Super-Venus exoplanet
The new work that GJ 1214 b or Enaiposha has an atmosphere dominated by carbon dioxide (CO2). So it’s something not seen before, a super-sized Venus. Lead author of the University of Arizona paper, Everett Schlawin, called it:
… a new class of planet.
Are the researchers now certain? No. They caution their findings are still tentative. Kazumasa Ohno at the National Astronomical Observatory of Japan explained:
The detected CO2 signal from the first study is tiny, and so it required careful statistical analysis to ensure that it is real. At the same time, we needed the physical and chemical insights to extract the true nature of GJ 1214 b’s atmosphere from Schlawin’s study.
Schlawin added:
It’s equivalent to Leo Tolstoy’s ‘War and Peace.’ If I gave you two copies and changed one sentence in one of the books, could you find that sentence?
Ohno’s team then used theoretical models to evaluate the most likely composition of the atmosphere. The Venus model – a carbon dioxide atmosphere – came out on top, bolstering the other findings.
More studies needed
So the researchers will need further study to conform the super-Venus scenario. But the results so far suggest even more diversity among exoplanets than we knew. Indeed, some, or many, are unlike any planets in our own solar system. Super-Venuses would be a fascinating addition to the exoplanet family. And this might be our first glimpse of one. Murphy said:
Although we’re not setting foot on another planet and walking around, we’re really pioneers. We’re the first humans to see what’s happening on this other planet. It’s amazing what you can do when you have a team from all over the globe.
Bottom line: Astronomers thought that exoplanet GJ 1214 b was either a watery super-Earth or a mini-Neptune. But a new study says it is more like a super-Venus exoplanet.
Source: Possible Carbon Dioxide above the Thick Aerosols of GJ 1214 b
Source: A Possible Metal-dominated Atmosphere below the Thick Aerosols of GJ 1214 b Suggested by Its JWST Panchromatic Transmission Spectrum
Via National Astronomical Observatory of Japan
Via The University of Arizona
Read more: Super-Earth may have water as steam or high clouds
Read more: Super-Earth, mini-Neptune or sub-Neptune?