- GJ 3378b is a super-Earth exoplanet about 25 light-years away. It is about twice the size of Earth.
- The planet is in the habitable zone of its red dwarf star, where liquid water could exist. But does it have an atmosphere?
- We don’t know yet if GJ 3378b has an atmosphere. If it does, it could possibly be rather Earth-like and habitable.
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Nearby super-Earth planet could be habitable
Astronomers have discovered a new Earth-like planet that might be a good candidate for habitability. The exoplanet, GJ 3378b, is about twice the size of Earth and 25 light-years away. The team of researchers, led by the University of California, Irvine, said on June 30, 2026, that the planet is in the habitable zone of its red dwarf star. That means it could have liquid water on its surface, if it has an atmosphere. So this planet could be habitable. But we don’t have enough data to know that yet.
The size of the planet makes it a super-Earth. Those are rocky planets that are larger than Earth but smaller than Neptune.
The team used the Habitable-zone Planet Finder instrument on the Hobby-Eberly Telescope at the McDonald Observatory in Texas to observe the planet’s host star. Astronomers first identified GJ 3378b as a candidate planet in 2024. And now, it is a confirmed planet.
The new observations also refined the planet’s orbit from 25 days to 21. That’s a lot less than Earth’s at 365 days, but the planet also orbits much closer to its red dwarf star, which is smaller and cooler than our sun.
The researchers published the peer-reviewed details of the new discovery in The Astrophysical Journal on June 30, 2026.
In the habitable zone
GJ 3378b is in the habitable zone of its star, a good location for potential habitability. That’s the region where temperatures could allow liquid water to exist on a planet’s surface, though whether it actually does also depends on its own atmosphere and composition. The planet does receive a suitable amount of radiation from its star, as lead author Paul Robertson at UC Irvine stated:
This super-Earth gets about 90% of the radiation from its host star as Earth gets from its sun, so it’s right in the sweet spot.
This one’s exciting. It’s one of our closest cosmic neighbors. 25 light-years sounds like a long way, but the Milky Way is about 100,000 light-years across, so in that respect it’s our next-door neighbor.
He added:
Our mantra is ‘follow the water.’ It’s the one thing every known living thing on Earth needs, so that’s the first thing we look for when trying to find environments that could sustain life.
Does GJ 3378b have an atmosphere?
What we know so far about GJ 3378b sounds promising in terms of habitability. But there’s still one big question: does the planet have an atmosphere? We don’t know yet. It’s in the habitable zone, but it’s also at the edge of what scientists call the cosmic shoreline. If a planet is outside of that boundary, closer to the star, then radiation from the star could strip away the planet’s atmosphere. This is common with planets close to red dwarf stars.
But GJ 3378b is right at the edge of this boundary. And we don’t know yet if it still has an atmosphere or if it had one and lost it. Ideally, the planet would have a thin, evolved atmosphere like Earth’s — nitrogen-based, not the thick, hydrogen-dominated “primordial” atmosphere a planet is born with. A more Earth-like atmosphere could maintain liquid water, as Robertson explained:
If you scale the Earth down to the size of an apple, its atmosphere would be about as thick as the skin of the apple. That’s just enough to maintain the kinds of surface pressures where you can have liquid water. It’s enough that there’ll be breathable air, and it provides maybe a little bit of protection from the harsh radiation environment of space.
Searching for signs of life on GJ 3378b
Right now, we don’t know if GJ 3378b is even habitable, let alone has life of any kind. But scientists want to take a closer look. NASA’s planned Habitable Worlds Observatory, for example, scheduled to launch sometime in the 2040s, would be able to take direct images of the planet. That, or perhaps other telescopic observations before then, will help determine whether GJ 3378b could actually support life. And then scientists could search for biosignatures, chemical or other signs of life in the planet’s atmosphere.
Gogod James, a UC Irvine student, said:
If a planet in the habitable zone has a proper atmosphere, we can justify further research looking for biosignatures, liquid water or other signs of life that require both an atmosphere and the right amount of heating from the host star.
The search for biosignatures continues
As Michael Endl, an astronomer at UT Austin, noted:
The ultimate goal is biosignatures. We really want to know, ‘Are we alone in the universe?’ We are still in the reconnaissance phase of our solar neighborhood, trying to find the planets around the nearest stars because those will be the easiest ones to detect a biosignature on. This planet brings us one step closer to knowing all of our neighbors and, ultimately, which might be hospitable for life.
For Robertson, the prospect of searching for life on GJ 3378b is something to savor:
I think that’s just too much fun.
Bottom line: Astronomers have gotten a closer look at the nearby super-Earth GJ 3378b. It could be habitable, if it has an atmosphere.
Source: A Revised Mass and Period for the Habitable Zone super-Earth GJ 3378 b: A Planet Straddling the Cosmic Shoreline
Via UC Irvine
Via McDonald Observatory
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