Astrónomos identifican una supertierra potencialmente habitable a solo 25 años luz

A team of astronomers at the University of California, Irvine has fundamentally redrawn what we know about GJ 3378b, a rocky world orbiting a red dwarf star just 25 light-years away. The findings, published on July 1st in The Astrophysical Journal, transform what was once thought to be a small gas giant into something far more intriguing: a superearth—a rocky planet that sits squarely within the habitable zone of its host star, where liquid water could theoretically exist.

The planet itself was first detected in 2024, but those initial observations painted a different picture. Early estimates suggested GJ 3378b was roughly 5.3 times Earth's mass and completed an orbit every 24.73 days, characteristics that pointed toward a mini-Neptune wrapped in a thick gaseous envelope. That classification mattered enormously, because gas giants, no matter how small, are not the kind of worlds where life as we understand it takes root. But the new research, which combined data from multiple high-precision spectrographs, arrived at a strikingly different conclusion. The planet's mass dropped to 2.3 times Earth's, its orbital period shortened to 21.45 days, and its distance from its star settled at approximately 0.097 astronomical units. That reduction in mass tips the scales decisively: GJ 3378b is almost certainly rocky, not gaseous.

What makes the discovery genuinely significant is where this planet sits in relation to its star. GJ 3378b receives roughly 90 percent of the solar energy that Earth receives from the Sun—enough to place it within what astronomers call the habitable zone, or the "Goldilocks region," where conditions might allow water to remain liquid on a planet's surface, provided that planet has an atmosphere to trap heat. The cosmic proximity adds a layer of wonder to the finding. Paul Robertson, the study's lead author, captured this sense of scale: from our vantage point, 25 light-years sounds impossibly distant, yet the Milky Way itself stretches across 100,000 light-years. In that context, GJ 3378b orbits one of our nearest cosmic neighbors.

Yet the discovery also exposes the limits of current knowledge. The central unanswered question is whether GJ 3378b possesses an atmosphere—or ever did. The planet sits right at the edge of what researchers call the "cosmic shoreline," the orbital zone where a star's radiation can gradually strip away a planet's gaseous envelope. Mars offers a cautionary tale from within our own solar system. Billions of years ago, the red planet likely had an atmosphere much like Earth's, but solar radiation eventually destroyed it, leaving behind the barren world we observe today. GJ 3378b may have suffered the same fate, or it may still be losing its atmosphere now.

For now, existing technology cannot answer that question. Astronomers will have to wait for the next generation of observatories to come online before they can determine whether GJ 3378b actually retains an atmosphere. That confirmation will be crucial. As Gogod James, another researcher on the team, explained, if a planet in the habitable zone has the right atmospheric composition, it becomes worth investigating further for biosignatures—evidence of water, chemical markers of life, or other signs that something living might exist there. Without an atmosphere, even a planet perfectly positioned in the habitable zone remains a dead rock. With one, it becomes a genuine candidate for life. The answer, for now, remains locked away in the darkness 25 light-years distant.