What is HD 137010b and why is it significant?

HD 137010b is an Earth-sized rocky planet candidate orbiting a Sun-like star approximately 150 light-years from Earth, discovered using data from NASA's Kepler Space Telescope. It's significant because it's the first planet candidate with Earth-like size orbiting in the habitable zone of a Sun-like star bright enough for substantial follow-up observations—marking a historic achievement in the 30-year quest for Earth analogs.

How was HD 137010b discovered and what role did citizen scientists play?

HD 137010b was discovered by analyzing archival Kepler K2 mission data from 2017. Citizen scientists participating in the Planet Hunters crowdsourced project initially flagged the faint transit signal. Professional astronomers then conducted rigorous validation and analysis, confirming the planetary interpretation. This collaboration between amateur and professional astronomy demonstrates the continuing value of citizen science.

Why is HD 137010b considered "potentially habitable" despite its cold surface temperature?

HD 137010b orbits in the habitable zone—the region where liquid water could exist on a planetary surface. While its surface is estimated to be -70°C (colder than Mars), it could still potentially host subsurface liquid water oceans maintained by internal heat, much like some moons in our solar system. The planet's 50% habitability probability reflects uncertainty in atmospheric composition and internal structure.

What observations are needed to confirm HD 137010b as a true exoplanet?

HD 137010b currently requires additional transit observations for full confirmation—the "gold standard" is three transits. At least one more transit is expected in late 2026 or early 2027. Once confirmed, future telescopes like NASA's planned Habitable Worlds Observatory could characterize the planet's atmosphere, revealing whether it contains water vapor, oxygen, or other molecules indicating biological activity.

HD 137010b Earth-Like Exoplanet Habitable Zone Discovery

On January 27, 2026, an international team of astronomers announced a discovery that represents the culmination of three decades of exoplanet science: HD 137010b, an Earth-sized rocky planet orbiting a Sun-like star in the habitable zone, located just 150 light-years from Earth. The discovery, published in The Astrophysical Journal Letters and led by researchers at the University of Southern Queensland in collaboration with institutions across the United States and United Kingdom, marks a profound milestone in humanity's search for potentially habitable worlds beyond our solar system. Unlike many previous exoplanet discoveries that resulted from theoretical predictions or systematic surveys, HD 137010b emerged from an unexpected source: citizen scientists participating in the Planet Hunters crowdsourced project, who spotted subtle signals in archival data from NASA's Kepler Space Telescope collected in 2017. The planet is only 6% larger than Earth, orbits its host star in approximately 355 days—nearly identical to Earth's 365-day year—and occupies a position near the outer edge of the habitable zone, the region where liquid water could theoretically exist on a planetary surface. While its surface temperature is estimated to be extremely cold, potentially colder than Mars at around -70 degrees Celsius, the discovery represents precisely what researchers have sought: a rocky, Earth-sized world in the habitable zone of a Sun-like star. The implications are profound. For the first time, humanity has identified a planet that could potentially harbor liquid water, essential for life as we understand it, around a star similar to our Sun and within a distance accessible to future powerful telescopes. If confirmed through additional observations—a crucial next step requiring at least one more transit detection—HD 137010b would stand alone as the only confirmed rocky world in the habitable zone of a Sun-like star, a distinction that would transform how we understand the frequency of potentially habitable planets in the galaxy and inspire a new generation of astronomers to search for life beyond Earth.

Three Decades of Discovery: The Quest for Earth Analogs

In October 1995, Swiss astronomers Michel Mayor and Didier Queloz announced the discovery of 51 Pegasi b, the first exoplanet ever found orbiting a Sun-like star. Their discovery fundamentally changed astronomy. Before 1995, every known planet existed within our solar system. After 1995, it became clear that planets were ubiquitous, likely present around the vast majority of stars. For the first time, the question "Are there other Earths?" became scientifically tractable rather than purely philosophical. In the three decades since that landmark discovery, exoplanet science has experienced exponential growth. Astronomers have confirmed the existence of over 6,000 exoplanets, with thousands more candidate discoveries awaiting confirmation. Sophisticated statistical analyses estimate that billions of planets populate the Milky Way alone. Yet despite this explosive growth in exoplanet discoveries, one category has remained elusive: Earth-analog planets—rocky worlds roughly the size of Earth, orbiting in the habitable zones of Sun-like stars. The habitable zone, also called the Goldilocks zone, represents the region around a star where planetary temperatures permit liquid water to exist on a surface. Too close to the star, and temperatures soar above boiling; too far, and the planet freezes into an ice ball. Finding planets in this narrow zone has proven technically challenging. Rocky planets are harder to detect than gas giants because they produce weaker signals in the primary detection methods. Earth-analogs are even more challenging because their small size and low mass make them nearly invisible to most detection techniques. The discovery of HD 137010b represents the first time astronomers have confirmed the detection of an Earth-sized rocky planet in the habitable zone of a Sun-like star bright enough for substantial follow-up observations, marking a watershed moment in the search for potentially habitable worlds.

From Archive to Discovery: The Role of Citizen Science and Kepler Data

The Kepler Legacy: A Decommissioned Telescope with Endless Data

The NASA Kepler Space Telescope, launched in 2009, revolutionized exoplanet science through its ability to detect transits—the subtle dimming of a star's light when a planet passes in front of it. Kepler monitored roughly 150,000 stars continuously, searching for these tiny brightness dips. Over its operational lifetime, Kepler discovered more than 2,600 confirmed exoplanets, more than doubling the total exoplanet count at the time of its decommissioning in 2018. Yet Kepler's contribution to exoplanet science extends far beyond its primary mission. After its main mission concluded, Kepler was repurposed as K2, a mission collecting data on different fields across the sky. The K2 mission generated enormous datasets containing photometric light curves—precise measurements of stellar brightness over time. These archives remain a treasure trove for exoplanet researchers, who analyze the data using sophisticated algorithms and human intuition. Much of HD 137010b's historical data came from K2 observations collected in 2017, nearly a decade before the discovery announcement. The light curve containing the planet's signal sat in NASA's public archives, awaiting analysis by researchers with the tools, expertise, and insight to extract its secrets.
Citizen Science Breakthrough: Planet Hunters and Human Pattern Recognition

In 2010, the Zooniverse project launched Planet Hunters, a citizen science initiative inviting members of the public to analyze Kepler light curves and search for transit signals that automated algorithms might miss. The rationale was sound: human visual pattern recognition can sometimes identify subtle signals that computer algorithms overlook, especially when those signals are faint or exhibit unusual characteristics. Thousands of volunteers worldwide participated in Planet Hunters, meticulously examining light curves for the characteristic dips indicating planetary transits. The crowdsourced effort proved remarkably successful, with citizen scientists contributing to the discovery of dozens of exoplanets. One of these volunteers was Alexander Venner, the lead author of the HD 137010b discovery paper, who participated in Planet Hunters while still in secondary school. Venner's early exposure to exoplanet research through citizen science sparked his passion for astronomy, eventually leading him to pursue a research career at the University of Southern Queensland. The faint signal indicating HD 137010b was initially flagged by Planet Hunters participants who recognized a subtle transit signature in the star's light curve. This flagging by citizen scientists, combined with rigorous follow-up analysis by professional astronomers, led directly to the discovery announcement. The breakthrough thus represents a beautiful collaboration between professional and amateur astronomy, demonstrating the continuing value of citizen science in an era of automated surveys and machine learning.
Detection Challenges and Signal Validation

Confirming an exoplanet discovery requires more than identifying a transit signal in archival data. Rigorous validation is necessary to rule out false positives. A transit signal could arise from various sources: a genuine planetary transit (what astronomers hope for); background stars in the telescope's field of view; instrumental artifacts or noise; or other stellar phenomena. The research team employed multiple validation techniques to confirm that the signal originated from an actual planet rather than a false positive. They analyzed the light curve characteristics, including the transit depth (how much the star's brightness decreased), duration, and shape. These properties must be consistent with a planet of the inferred size and orbital period orbiting a star of the observed properties. The researchers also examined the host star's properties in detail, using spectroscopic observations to measure the star's temperature, composition, and size. The star proved to be a K-dwarf—a relatively cool star about 70% the Sun's size and roughly 1,000 Kelvin cooler than our Sun. With the star's properties confirmed, the transit signal's characteristics could be interpreted to infer the planet's properties: approximately Earth-sized and rocky, with an orbital period of about 355 days. The validation process, though rigorous, ultimately provided strong evidence supporting the planetary interpretation, though not absolutely certain confirmation—hence the designation "planet candidate" rather than a confirmed exoplanet. That designation will change if additional transit observations are detected.

Analysis I: Habitability Assessment and the Ice-Cold Dilemma

Habitable Zone Definition: Where Water Can Remain Liquid

The habitable zone—also called the circumstellar habitable zone (CHZ) or Goldilocks zone—represents a region around a star where planetary surface temperatures could allow liquid water to exist. Liquid water is essential for all known forms of life and serves as the foundation for the definition of habitability used in exoplanet science. The habitable zone's extent depends on the star's luminosity (total energy output). A more luminous star requires planets to orbit farther away to receive a comparable amount of radiation. A dimmer star requires planets to orbit closer. The Sun's habitable zone extends from roughly 0.95 AU (the orbit of Venus) to approximately 1.37 AU (beyond Earth's orbit), though estimates vary depending on atmospheric assumptions and other factors. HD 137010's star, a K-dwarf with about 30% of the Sun's luminosity, has its habitable zone shifted inward. A planet receiving the same radiation as Earth would orbit closer to an M-dwarf than to the Sun. HD 137010b orbits at 0.88 AU from its host star, comparable to Earth's 1 AU distance from the Sun. However, because the K-dwarf is significantly dimmer, the planet receives considerably less solar energy than Earth—roughly one-third of Earth's radiation. This places the planet near the outer edge of the habitable zone, where temperatures would be cold but where water could theoretically remain liquid, particularly if the planet possesses a greenhouse atmosphere capable of retaining heat.
Surface Temperature and Mars-Like Conditions

Current models suggest HD 137010b's surface temperature would be approximately -70 degrees Celsius (about -94 degrees Fahrenheit), making it potentially colder than Mars, which averages about -65 degrees Celsius. This bone-chilling temperature reflects the planet's position at the outer edge of the habitable zone, receiving insufficient solar radiation to warm the surface substantially. For liquid water to exist on such a cold world, the planet would require either a particularly robust greenhouse atmosphere—with carbon dioxide, methane, or other heat-trapping gases—or a different heat source. One intriguing possibility involves subsurface liquid water. Even if the surface is frozen, subsurface oceans could potentially exist if the planet possesses sufficient internal heat from radioactive decay or tidal heating. Earth's moon lacks significant internal heating, but some planetary moons in our solar system—particularly those orbiting gas giants—show evidence of subsurface liquid water maintained by tidal friction. If HD 137010b possesses similar subsurface hydrology, microbial life could potentially survive in these hidden oceans, even if the surface remains frozen. The researchers acknowledge these challenges explicitly. Lead author Alexander Venner described the planet as being "at the limits of what we think might be possible in terms of potential habitability," emphasizing that the habitability assessment is tentative and dependent on poorly understood factors like atmospheric composition and internal structure.
50% Habitability Probability: Quantifying Uncertainty

The research team's assessment that HD 137010b has approximately a 50% probability of residing in the habitable zone reflects the substantial uncertainties inherent in planetary habitability determinations. This probability arises from multiple sources of uncertainty: the planet's orbital eccentricity (how elliptical its orbit is), the planet's atmospheric composition (completely unknown for an exoplanet at such distance), the planet's internal thermal structure, and other factors. The team notes that there is approximately a 40% chance the planet orbits somewhat closer to its star than currently estimated, placing it more firmly within the habitable zone and ensuring higher surface temperatures. Conversely, there's a similar probability that the planet orbits somewhat farther away, placing it outside the traditional habitable zone boundaries. These uncertainties highlight a crucial point: estimating a distant planet's habitability from limited data is inherently uncertain. Conclusions drawn about HD 137010b's habitability must be regarded as preliminary and subject to revision as more observational data accumulates. Nevertheless, the 50% probability of habitability makes HD 137010b a compelling target for future observations and detailed characterization.

Analysis II: Comparative Context and Future Observations

HD 137010b in the Exoplanet Landscape: A Unique Discovery

The exoplanet census includes thousands of worlds, yet HD 137010b occupies a unique position. Many known habitable zone planets orbit M-dwarfs (red dwarf stars considerably dimmer than our Sun). The next best rocky planet candidate in the habitable zone of a Sun-like star—Kepler-186f, discovered in 2014—orbits a star nearly 200 light-years away, making it 4 times more distant than HD 137010b's star. Additionally, Kepler-186f is roughly 20 times fainter in visible light, making detailed follow-up observations far more challenging. Another candidate, Proxima Centauri b, orbits in the habitable zone of the closest star to Earth but around an M-dwarf significantly different from our Sun. HD 137010b's distinction is that it is (1) Earth-sized, (2) in a habitable zone, (3) around a Sun-like star, and (4) at a relatively nearby distance permitting substantial follow-up observations. This unique combination of properties explains the excitement surrounding the discovery and why Dr. Jessie Christiansen, chief scientist at NASA's Exoplanet Science Institute, called the discovery "incredibly tantalizing." The research team emphasizes this point: "This is the first planet candidate with Earth-like radius and orbital properties that transits a Sun-like star bright enough for substantial follow-up observations."
Confirmation Pathway and Future Telescopes

HD 137010b's current designation as a "planet candidate" rather than a confirmed exoplanet reflects the need for additional observational confirmation. The gold standard for exoplanet confirmation involves detecting multiple transits—NASA's Exoplanet Science Institute requires at least three independent transit observations to classify a world as a confirmed exoplanet rather than a candidate. HD 137010b has been observed in transit once (the single detection in 2017). Astronomers now await at least one, ideally two or three, additional transit observations to achieve confirmation status. These future transits will occur periodically, based on the planet's 355-day orbital period. The most imminent transit opportunity occurs in late 2026 or early 2027. Given the star's moderate brightness (10th apparent magnitude), ground-based telescopes with sufficient aperture and precision photometry capabilities should be able to detect the transit. The James Webb Space Telescope, with its extraordinary infrared sensitivity, could confirm a transit, though dedicated observations of a relatively faint source would consume valuable telescope time. Future dedicated exoplanet-imaging missions, like NASA's planned Habitable Worlds Observatory (successor to JWST), could not only confirm HD 137010b through transit detection but also potentially characterize its atmosphere through spectroscopy, revealing whether it possesses water vapor, oxygen, or other biosignatures.
Implications for Planet Frequency and the Drake Equation

If HD 137010b's confirmation (and several other recent candidate discoveries) represents an emerging population of Earth-sized planets in habitable zones of Sun-like stars, it carries profound implications for estimates of potentially habitable planet frequencies. Astronomers use the Drake Equation—a framework for estimating the number of communicative civilizations in our galaxy—to organize thinking about exoplanet populations and habitability. The equation's terms include the fraction of stars with planets, the fraction of planets in habitable zones, and the fraction of habitable planets that develop intelligent life. Pre-HD 137010b estimates suggested that Earth-analogs around Sun-like stars might be relatively rare, perhaps comprising only a few percent of planetary systems. If HD 137010b joins a growing population of similar worlds, it would suggest that Earth-analogs are far more common than previously thought, potentially orders of magnitude more abundant. Such a revision would dramatically increase estimates of potentially habitable worlds in the galaxy, with profound implications for the likelihood of life elsewhere in the cosmos.

Discussion: The Future of Earth-Analog Searches

Mining Archival Data: Untapped Resources for Discovery

The discovery of HD 137010b from archival Kepler data collected nearly a decade earlier underscores an important point: massive datasets from past missions contain discoveries awaiting analysis. As computational techniques improve and researchers apply machine learning and crowdsourced analysis to existing data, additional Earth-analog candidates will likely emerge from archives. The ongoing analysis of TESS (Transiting Exoplanet Survey Satellite) data, which is systematically surveying the entire sky for transiting planets, will accelerate this process. TESS has already discovered thousands of exoplanet candidates, many awaiting confirmation. Future missions will generate even larger datasets. The trend toward discovery through archival analysis suggests that Earth-analogs may be more common than realized, and systematic exploitation of existing data could yield dozens of additional candidates in coming years.
Atmospheric Characterization: Biosignatures and Technosignatures

Once confirmed, HD 137010b will become a priority target for atmospheric spectroscopy—observations designed to determine the planet's atmospheric composition. This characterization will reveal whether the planet possesses water vapor, oxygen, methane, or other molecules. Some combinations (like oxygen with methane) could represent biosignatures—signatures indicative of biological processes. Detecting biosignatures on an exoplanet would provide the strongest evidence to date for extraterrestrial life, a discovery that would revolutionize our understanding of the cosmos. The technical challenges are immense; characterizing the thin exoplanet atmosphere against the glare of its host star requires extraordinary instrumental sensitivity. Yet the next generation of ground-based telescopes (extremely large telescopes with mirrors exceeding 20-30 meters) and space-based missions (Habitable Worlds Observatory) are designed specifically to achieve this capability. HD 137010b, at 150 light-years distance around a relatively bright Sun-like star, represents an ideal target for this quest.
A Turning Point in the Search for Life Beyond Earth

The discovery of HD 137010b may represent a turning point in humanity's quest to answer the ancient question: "Are we alone in the universe?" For the first time, astronomers have identified a rocky planet that is Earth-sized, orbiting in the habitable zone of a Sun-like star, at a distance accessible for detailed future observations. The planet is not yet confirmed, its surface is likely frigid, and whether it actually harbors life remains an open question. Yet it represents concrete progress toward identifying potentially habitable worlds and the possibility of eventually detecting biosignatures from a genuinely Earth-like exoplanet. As additional Earth-analogs are discovered, as future observatories improve atmospheric characterization capabilities, and as our understanding of habitability deepens, the quest to find life beyond Earth will shift from speculation to evidence-based investigation. HD 137010b symbolizes this transition—a discovery that transforms the question "Could there be life on other worlds?" into the more specific "Is there life on that specific world?"

Conclusion: Earth's Twin—And the Future of Habitability Science

HD 137010b is not, in the most literal sense, Earth's twin. Its surface is far colder, its host star is dimmer, and its orbital environment differs from Earth's in numerous ways. Yet in the most profound sense—as a potentially habitable rocky world orbiting a Sun-like star—it represents the closest analog to Earth that astronomers have confirmed in the habitable zone. The discovery emerged not from any single brilliant insight but from the convergence of multiple advances: three decades of exoplanet discoveries providing context; sophisticated instrumentation like Kepler detecting subtle planetary signals; archival data preserving observations for future analysis; citizen scientists applying human pattern recognition to light curves; and professional astronomers employing rigorous validation and characterization techniques. The combination of these elements yields a discovery that stands alone in exoplanet science: an Earth-sized rocky world in the habitable zone of a Sun-like star, close enough for detailed future observations, representing humanity's best shot at discovering whether life exists beyond Earth. As the community awaits confirmation through additional transit observations and undertakes detailed atmospheric characterization with next-generation telescopes, HD 137010b will occupy a unique place in astronomy—a symbol of how far we have come in understanding our cosmic context and how much further we can go in the century ahead.