Nearby 'super-Earth' is our best chance yet of finding extraterrestrial life

Astronomers have spotted a likely rocky “super-Earth” just under 20 light-years away – one that could potentially support life. The planet, GJ 251 c, appears to be almost four times Earth’s mass.

What has scientists excited is that it orbits in the habitable zone around its star – the region where liquid water could persist if conditions are right.

After two decades of observations, the signal stands out as one of the most promising nearby targets for probing the atmospheres of small worlds.

The discovery comes from an international collaboration that includes researchers from Penn State University.

Their work weaves together long-baseline measurements from multiple observatories with new, ultra-precise spectra.

The result reveals a second planet in the GJ 251 system – one that sits in the coveted “Goldilocks” band around its star.

Looking for life on super-Earth GJ 251 c

“We look for these types of planets because they are our best chance at finding life elsewhere,” said Suvrath Mahadevan, a professor of astronomy at Penn State and co-author of the paper.

“The exoplanet is in the habitable or the Goldilocks zone, the right distance from its star that liquid water could exist on its surface, if it has the right atmosphere.”

That context is crucial. A rocky planet close by, circling in temperate light from a small, quiet star, gives future telescopes a fair shot at reading atmospheric fingerprints.

These include gases like oxygen, methane, or carbon dioxide that can hint at surface conditions – and even biological processes.

Finding GJ 251 c with wobbles

For years, astronomers tracked subtle tugs on GJ 251 – the tiny stellar wobble caused by an orbiting planet. These Doppler shifts are minuscule, easily masked by the star’s own magnetic changes.

The team first refined the signal of an inner world, GJ 251 b, which loops around the star every 14 days.

With that baseline nailed down, they folded in fresh, high-precision data. This revealed a second, slower rhythm – a 54-day signal pointing to a more massive planet farther out, GJ 251 c.

The detection rests on patient accumulation of measurements across instruments and years, followed by sophisticated modeling to separate planets from stellar static.

The result was a coherent, periodic signature that fits the criteria for a super-Earth in the habitable zone.

Instruments built for this moment

The breakthrough leaned on the Habitable-Zone Planet Finder (HPF). It’s a near-infrared spectrograph mounted to the Hobby-Eberly Telescope in Texas. It was designed to detect small planets orbiting cool, nearby stars.

“We call it the Habitable Zone Planet Finder, because we are looking for worlds that are at the right distance from their star that liquid water could exist on their surface. This has been the central goal of that survey,” Mahadevan said.

“This discovery represents one of the best candidates in the search for atmospheric signatures of life elsewhere in the next five to ten years.”

To lock down the case, the team also tapped NEID, another ultra-stable spectrometer, to independently confirm the 54-day rhythm.

Multiple instruments and multiple sites led to one consistent story: GJ 251 c is definitely a temperate super-Earth that stands out from the noise with the potential for life.

Beating the star at its own game

One of the biggest challenges is that stars are noisy. Starspots rotate in and out of view. Magnetic fields flare, and convective cells churn. Each effect can mimic a planet’s pull.

The team attacked that problem by comparing how the star’s spectrum changes across different wavelengths. They also trained custom models on the combined dataset.

“This is a hard game in terms of trying to beat down stellar activity as well as measuring its subtle signals, teasing out slight signals from what is essentially this frothing, magnetospheric cauldron of a star surface,” Mahadevan said.

“This discovery is a great example of the power of multi-disciplinary research at Penn State,” said Eric Ford, the director of research for Penn State’s Institute of Computational & Data Sciences (ICDS).

“Mitigating stellar activity noise required not just cutting-edge instrumentation and telescope access, but also customizing the data science methods for the specific needs of this star and combination of instruments,” Ford concluded.

Lining up the next leap

Directly photographing a small, dim planet next to a bright star remains out of reach for today’s instruments, but not for long.

“We are at the cutting edge of technology and analysis methods with this system,” said Corey Beard, corresponding author on the paper. “We need the next generation of telescopes to directly image this candidate, but what we also need is community investment.”

Engineers are building 30-meter-class observatories equipped with advanced coronagraphs and high-dispersion spectrographs. These instruments will detect atmospheres on nearby rocky worlds.

One of the most promising targets is GJ 251 c. If the planet hosts air, its gases could betray surface conditions and potential habitability.

Lessons from GJ 251 c

The discovery showcases how sustained, global efforts add up. It took decades of observing time, coordinated hardware built expressly to chase tiny Doppler shifts, and custom analytics to make sense of a stubbornly faint signal.

“We are always focused on the future,” Beard said. “Whether that’s making sure the next generation of students can engage in cutting-edge research or designing and building new technology to detect potentially habitable planets.”

“While we can’t yet confirm the presence of an atmosphere or life on GJ 251 c, the planet represents a promising target for future exploration,” said Mahadevan. “We made an exciting discovery, but there’s still much more to learn about this planet.”

GJ 251 c checks the right boxes: nearby, likely rocky, and sitting in its star’s temperate zone. It’s not a world we can clearly observe today, but it’s ideally placed for the telescopes coming online soon.

As those facilities switch on, this super-Earth will be high on the target list for potential life. It’s a reminder that patient measurements and purpose-built tools can turn faint stellar jitters into the next big step in the search for life.

The full study is published in the The Astronomical Journal.

Featured image: An international team of scientists, including researchers at Penn State, dubbed the exoplanet, named GJ 251 c, a “super-Earth” as data suggest it has a rocky composition similar to Earth and is almost four times as massive. Credit: Illustration by University of California Irvine

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–