A potentially habitable world. Rocky. Sitting just 25 light-years out.
It sounds far away. It’s not, really.
Paul Robertson at UC Irvine calls it “our next-door neighbor.” In the context of a Milky Way stretching 100,00 light-years across, that is practically the house down the street. The planet is named GJ 3378. It orbits a dim red dwarf in the Giraffe constellation.
French astronomers found it in 2024. They used the Canada–France–Hawai‘i Telescope. Then American researchers took another look. They corrected the record.
“This one’s exciting.”
The first draft said it was heavy. Five times Earth’s mass. A mini-Neptune, mostly gas, not much rock. Not really Earth-like.
New data changes that. Robertson’s team checked it again with different telescopes. The real mass? Only 2.3 times Earth’s.
That moves it out of gas giant territory. It puts it firmly in super-Earth range. Rocky surface. Maybe land. Maybe sea.
The orbit changed too. Originally thought to be 25 days. Actually 21. Closer to its star.
This puts GJ 337b squarely in the habitable zone.
Robertson notes the planet receives about 90% of the solar energy Earth does from our sun. A “sweet spot” for liquid water, provided the surface doesn’t boil or freeze.
So is it Earth?
We don’t know. It could be blue and green with clouds and cities. Or it could be a dead, airless cratered rock. We haven’t seen it pass in front of its star yet. No transit. That makes atmospheric study nearly impossible today.
We detected it because of gravity. The planet tugs on its star. The star wobbles. Spectra show the Doppler shift. We know it’s there. We don’t know what’s around it.
Here is the rub: Red dwarfs are angry stars. They spit radiation. Stellar winds blast outward in fierce gusts. They can strip a planet bare.
Does GJ 36b have an atmosphere left?
Right now? Impossible to tell.
The James Webb Space Telescope can look for atmospheres on transiting planets in systems like TRAPPIST-1. Light filters through the gas, leaving dark fingerprints in the spectrum.
GJ 36 doesn’t transit. Webb can’t see the atmosphere, even if it exists.
We have to wait. The Habitable Worlds Observatory won’t launch until the 204s. That’s two decades of patience.
There is hope, though. GJ 6 sits on the very edge of the radiation-blasted zone. It might have dodged the worst of the stellar wind. It might hold on to some air.
Michael Endl at the University of Texas sees the bigger picture. The goal is biosignatures. Signs of life. We are still just doing reconnaissance in our solar neighborhood.
“This planet brings us one step closer.”
To what? To knowing our neighbors. To seeing which ones are hospitable.
Will they answer when we call in twenty years? Maybe.
