BY:SpaceEyeNews.
Astronomers may have found one of the most intriguing rocky worlds in recent years. The planet candidate is called HD 137010 b, and it stands out for a simple reason: it looks unusually Earth-like in both size and orbital timing. Early analysis suggests it is only slightly larger than Earth and circles its star in about 355 days, which is very close to our own year. That combination is rare. It becomes even more interesting because the host star is relatively bright and sits about 146 light-years away, close enough for meaningful follow-up work.
This does not mean scientists have found another Earth. Not yet. HD 137010 b is still a planet candidate, not a fully confirmed planet. The reason is straightforward. Researchers have only seen one transit, meaning one single event where the object appeared to cross in front of its star and dim the starlight for about 10 hours. That one signal is compelling, but astronomy usually needs repeat evidence before a discovery becomes secure.
Even with that caution, HD 137010 b already matters. It offers a rare case where an Earth-size candidate with a near-Earth-length orbit circles a star bright enough for future atmospheric and orbital studies. That is exactly the kind of target astronomers hope to find when searching for potentially temperate rocky worlds beyond our solar system.
HD 137010 b emerged from one missed signal
The story behind HD 137010 b is part of what makes it so compelling. The signal did not come from a brand-new telescope campaign. It came from archived K2 data collected in 2017, when NASA’s repurposed Kepler mission was still watching stars for tiny brightness dips caused by transiting planets. Researchers later identified a very shallow event in the light curve of the star HD 137010. The dip measured about 225 parts per million and lasted around 10 hours. That faint dimming matched what astronomers would expect from a small rocky world crossing the face of the star.
The reason this signal stayed hidden for so long is important. Automated planet searches work best when they can find repeating transits. A planet with a short orbit crosses its star many times, so the pattern becomes easier for software to catch. HD 137010 b appears to orbit once every 355 days, so K2 only caught one crossing during the observing window. A single transit can be easy to overlook if your system is tuned for repetition.
That is why human review still matters. The signal was first flagged by volunteers in Planet Hunters, the citizen-science project that lets people inspect telescope light curves by eye. Lead author Alexander Venner and collaborators then studied the event in depth and concluded that a transiting planet candidate was the best explanation. NASA later highlighted the case as a discovery alert, emphasizing both the unusual detection and the need for additional confirmation.
Why HD 137010 b looks so Earth-like
Many exoplanets grab attention because they are giant, hot, or extreme. HD 137010 b stands out for the opposite reason. It seems modest. The candidate has an estimated radius of about 1.06 Earth radii, making it very close to Earth in size. Its estimated orbital period of 355 days, though still uncertain, puts it in a very familiar rhythm around its star. In broad terms, it is the kind of geometry astronomers have long hoped to find: a small rocky world moving on a long orbit around a stable star.
Its host star also helps. HD 137010 is a K-dwarf, meaning it is somewhat smaller and cooler than the Sun. The paper describes it as a tenth-magnitude K-dwarf, bright enough for stronger follow-up than many Earth-size candidates found around fainter stars. That brightness matters because astronomers need a healthy stream of photons to refine a planet’s orbit, search for additional worlds in the system, and eventually probe atmospheric properties if technology and geometry allow.
This is one reason researchers see HD 137010 b as unusually valuable. Plenty of small exoplanets exist, and some sit in interesting temperature zones, but many orbit stars that are too faint for detailed characterization. In contrast, this target combines a small estimated size, a long orbital period, and a relatively bright nearby star. In the search for Earth-like systems, that is a rare mix.
HD 137010 b may be cold, not comfortable
The phrase “Earth-like” can mislead people, so this is where the science gets more nuanced. HD 137010 b may resemble Earth in size and orbital timescale, but it likely does not receive Earth-like levels of energy. Because the host star is dimmer than the Sun, the planet gets only about 29% of the incoming stellar flux that Earth receives. The study places it near the outer edge of the habitable zone, not in an obvious temperate sweet spot.
That opens two very different climate possibilities. One version is a cold, icy world. If the surface reflects much of the incoming light and the atmosphere is thin, the planet could stay frozen over. NASA’s own discovery alert leaned into this uncertainty by calling the object an “ice-cold Earth?” with a question mark, which captures the scientific mood well.
The second version is more hopeful. A thicker atmosphere rich in carbon dioxide could trap heat through a greenhouse effect and keep surface temperatures high enough for liquid water under the right conditions. The paper estimates that HD 137010 b has roughly a 40% chance of falling within the conservative habitable zone, with somewhat better odds under a broader optimistic definition. That does not prove habitability, but it does keep the door open.
This tension is exactly why the system matters. HD 137010 b is not exciting because it is already confirmed as a living world. It is exciting because it sits in a scientifically useful gray zone. It is small. It is nearby. It gets limited starlight. And it may show how atmosphere, orbital placement, and host-star type work together to shape rocky planet climates.
Scientists tested whether HD 137010 b could be a false alarm
A single-transit discovery always raises a hard question: what if the signal is not a planet at all? Researchers took that problem seriously. According to the study, they checked historical and new imaging observations, archival radial velocity data, and astrometry to test other explanations. They aimed to rule out common false positives such as background stellar blends, eclipsing binaries, or an off-target source creating the dip.
The result was encouraging. The team concluded that the event appeared astrophysical, occurred on-target, and was best explained by a transiting planet candidate. NASA’s Exoplanet Archive also notes that HD 137010 b remains unconfirmed, which is consistent with the paper’s cautious wording. The candidate is notable enough to be discussed publicly, but it has not yet entered the confirmed-planet tables.
That distinction matters for good science communication. It keeps the story exciting without overstating the result. Right now, the cleanest description is this: HD 137010 b is a strong and unusually interesting Earth-size planet candidate that still needs a second transit or another independent line of confirmation.
Why HD 137010 b matters for future exoplanet missions
The long-term value of HD 137010 b lies in follow-up. If astronomers can catch another transit, they can tighten the orbit, improve size estimates, and study whether more planets share the system. That next transit is hard to schedule because the period is long and the current timing carries uncertainty. Researchers may only get narrow windows to watch, and missing one window can mean waiting many more months.
Another route is the radial velocity method, which looks for a tiny wobble in the star caused by the planet’s gravity. The challenge is scale. If HD 137010 b has a mass close to Earth’s, the stellar wobble would be extremely small and difficult for current instruments to detect cleanly. That makes confirmation possible in principle but demanding in practice.
This is where future observatories become important. The study and NASA both frame HD 137010 b as the kind of target that benefits from long-baseline monitoring and improved sensitivity. ESA’s upcoming PLATO mission is designed to find and study Earth-size planets around bright nearby stars, especially those on wider orbits. Even though PLATO did not discover this candidate, the system fits the broader scientific goal that missions like PLATO are built to serve.
There may also be more going on in the system. The paper notes hints that an additional outer object, perhaps a larger planet or even a brown dwarf, may be tugging on the star. That possible companion does not explain away the transit signal, but it could help researchers understand how the full system formed and evolved. In other words, HD 137010 b may matter not only as an isolated candidate, but as part of a more complex planetary architecture.
HD 137010 b gives astronomers a rare target
The search for an Earth analog is full of almosts. Some planets are the right size but orbit dim stars. Others orbit bright stars but are too large, too hot, or too close in. HD 137010 b earns attention because it lands in a much rarer overlap. It appears to be small, its orbit is long, its star is bright enough to matter, and the system is near enough for serious observation. That does not make it a second Earth. It makes it a rare opportunity.
For SpaceEyeNews readers, that is the real story. HD 137010 b shows that some of the most important exoplanet discoveries do not arrive with fireworks. Sometimes they begin as a quiet dip in old data, a missed signal, and a careful second look. If future observations confirm this world, it may become one of the best small-planet targets for studying rocky climates around nearby stars. If it turns out to be frozen, that still teaches us something valuable about the limits of habitability. Either way, HD 137010 b has already become one of the most interesting exoplanet candidates to watch.
Conclusion: HD 137010 b is worth watching
HD 137010 b deserves the attention it is getting. The candidate combines an Earth-size radius, a 355-day orbit, and a bright nearby K-dwarf host star in a way astronomers rarely get to study. It still needs confirmation, so caution remains essential. But as a target for future follow-up, HD 137010 b already stands out. Whether it proves icy, marginally temperate, or something in between, it gives astronomers a concrete world to investigate instead of a vague theoretical possibility. For now, that is enough to make HD 137010 b one of the most promising exoplanet stories of the year.
Main sources
- NASA Science — Discovery Alert: An Ice-Cold Earth?
https://science.nasa.gov/universe/exoplanets/discovery-alert-an-ice-cold-earth/ - arXiv / study preprint — A Cool Earth-sized Planet Candidate Transiting a Tenth Magnitude K-dwarf From K2
https://arxiv.org/abs/2601.19870 - NASA Exoplanet Archive — Exoplanet Archive News / candidate status note
https://exoplanetarchive.ipac.caltech.edu/docs/exonews_archive.html - Earth.com article shared in your prompt
https://www.earth.com/news/earth-size-planet-hd-137010-b-life-candidate-orbits-nearby-star-every-355-days/