HD 137010

{{Short description|High proper-motion star in the constellation Libra}} {{Starbox begin}} {{Starbox image | image = [[Image:HD_137010_Star.png|300px]] | caption = [[2MASS]] image of HD 137010 }} {{Starbox observe | epoch = J2000 | constell = [[Libra (constellation)|Libra]]<ref name=xhip>{{cite XHIP|75398}}</ref> | ra = {{RA|15|24|21.25106}}<ref name=dr3/> | dec = {{DEC|-19|44|21.6785}}<ref name=dr3/> | appmag_v = 10.14<ref name="SIMBAD"></ref> }} {{Starbox character | type = [[Main sequence]]<ref name="Alexander Venner et al (2026)" /> | class = K3.5 V<ref name="SIMBAD"></ref> }} {{Starbox astrometry | radial_v = +27.866<ref name="SIMBAD"></ref> | prop_mo_ra = +228.536<ref name=dr3/> | prop_mo_dec = −248.158<ref name=dr3/> | parallax = 22.2922 | p_error = 0.0174 | parallax_footnote = <ref name=dr3>{{cite Gaia DR3|6254679341809369088}}</ref> | absmag_v = +7.2<ref name=xhip/> }} {{Starbox detail | source = <ref name="Alexander Venner et al (2026)" /> | mass = {{Val|0.726|0.017}} | radius = {{Val|0.707|0.023}} | luminosity = {{Val|0.232|0.023|0.021}} | temperature = {{Val|4770|90|fmt=commas}} | metal_fe = -0.22 | gravity = {{val|4.60|0.03}} | age_gyr = 4.8-10 }} {{Starbox catalog | names = {{odlist | HD=137010 | HIP=75398 | PPM=230195 | EPIC=249661074 | BD=-19 4097 | TIC=428919267 }}<ref name="SIMBAD" /> }} {{Starbox reference |Simbad=HD%20137010 }} {{Starbox end}}

'''HD 137010''' is a [[K-type main-sequence star]] located approximately 146 light-years (44.86 parsecs) away in the [[zodiac]] constellation of [[Libra (constellation)|Libra]].<ref name="SIMBAD">{{cite simbad |title=HD 137010 |access-date=2026-01-27}}</ref><ref name="Alexander Venner et al (2026)">{{cite journal |arxiv=2601.19870 |last1=Venner |first1=Alexander |last2=Vanderburg |first2=Andrew |last3=X. Huang |first3=Chelsea |last4=Dholakia |first4=Shishir |last5=Schwengeler |first5=Hans Martin |last6=Howell |first6=Steve B. |last7=Wittenmyer |first7=Robert A. |last8=Kristiansen |first8=Martti H. |last9=Omohundro |first9=Mark |last10=Terentev |first10=Ivan A. |title=A Cool Earth-sized Planet Candidate Transiting a Tenth Magnitude K-dwarf From K2 |journal=The Astrophysical Journal |date=2026 |volume=997 |issue=2 |pages=L38 |doi=10.3847/2041-8213/adf06f |doi-access=free |bibcode=2026ApJ...997L..38V }}</ref> It is a [[solar analog]], though cooler, dimmer, and smaller than the [[Sun]], with an apparent visual magnitude of 10.14, making it invisible to the naked eye but readily observable with a telescope.<ref name=":EPA">{{Cite web |title=HD 137010 {{!}} NASA Exoplanet Archive |url=https://exoplanetarchive.ipac.caltech.edu/overview/HD%20137010 |access-date=2026-03-29 |website=exoplanetarchive.ipac.caltech.edu}}</ref> The star is notable for hosting the exoplanet candidate [[HD 137010 b]],<ref name="Martin-2026">{{Cite web |last=Martin |first=Pierre-Yves |date=2026|title=Planet HD 137010 b |url=https://exoplanet.eu/catalog/hd_137010_b--11844/ |access-date=2026-01-28 |website=exoplanet.eu |language=en}}</ref><ref name="Discovery-Alert-2026">{{Cite web |date=2026-01-27 |title=Discovery Alert: An Ice-Cold Earth? - NASA Science |url=https://science.nasa.gov/universe/exoplanets/discovery-alert-an-ice-cold-earth/ |access-date=2026-01-27 |language=en-US}}</ref> a potential Earth-sized exoplanet detected via a single transit in archival data from [[NASA]]'s [[Kepler space telescope|Kepler]] K2 mission.<ref name="Alexander Venner et al (2026)" />

==Characteristics== HD 137010 has a spectral type of K3.5 V,<ref>{{Cite journal |last1=Gray |first1=R. O. |last2=Corbally |first2=C. J. |last3=Garrison |first3=R. F. |last4=McFadden |first4=M. T. |last5=Bubar |first5=E. J. |last6=McGahee |first6=C. E. |last7=O'Donoghue |first7=A. A. |last8=Knox |first8=E. R. |date=July 2006 |title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc--The Southern Sample |url=https://iopscience.iop.org/article/10.1086/504637 |journal=The Astronomical Journal |language=en |volume=132 |issue=1 |pages=161–170 |doi=10.1086/504637 |issn=0004-6256|arxiv=astro-ph/0603770 }}</ref> indicating that it is a [[main-sequence]] star generating energy through the [[thermonuclear fusion]] of hydrogen in its core. Its [[effective temperature]] is 4,770 ± 90 K, giving the star an orange hue.<ref name="Alexander Venner et al (2026)" /><ref name=":EPA" /> The star's mass is 0.726 ± 0.017 {{solar mass}}, its radius is 0.707 ± 0.023 {{solar radii}}, and its luminosity is {{Val|0.232|0.023|0.021}} {{solar luminosity}}.<ref name="Alexander Venner et al (2026)" /> Its metallicity is slightly subsolar at [Fe/H] = −0.22 ± 0.07 dex.<ref name=":EPA" />

The star's age is estimated between 4.8 and 10 billion years (one analysis gives 7.4 ± 2.6 Gyr), consistent with its low magnetic activity.<ref name="Alexander Venner et al (2026)" /> Its surface gravity is log g = 4.60 ± 0.03 (cgs), and its density is {{Val|2.90|0.29|0.26}} g/cm³.<ref name=":EPA" />

HD 137010 was observed by the Kepler space telescope for 88 days during K2 Campaign 15 (23 August to 19 November 2017).<ref name="Alexander Venner et al (2026)" /> Photometry revealed a single, shallow 10-hour transit event with a depth of 225 ± 10 parts per million (ppm) and a duration of {{Val|9.76|0.21|0.18}} hours.<ref name=":EPA" /> The transit was identified through visual inspection of the light curve.<ref name="Alexander Venner et al (2026)" /> Analysis of the K2 photometry, high-resolution imaging (including new speckle observations), archival radial velocities, and Gaia/Hipparcos astrometry ruled out all conventional false-positive scenarios, such as background [[eclipsing binaries]], hierarchical triples, or instrumental artifacts. The event is best explained by a transiting planet candidate, designated HD 137010 b.<ref name="Alexander Venner et al (2026)" /><ref name="Discovery-Alert-2026" />

The candidate has a radius of {{Val|1.06|0.06|0.05}} {{Earth radius}}, consistent with a rocky [[Super-Earth]] or [[Earth analog]]. Assuming negligible orbital eccentricity, the orbital period is estimated at {{Val|355|200|59}} days, with a semi-major axis of {{Val|0.88|0.32|0.10}} AU.<ref name=":EPA" /> The planet receives an incident stellar flux of {{Val|0.29|0.11|0.13}} times that of Earth, placing it near the outer edge of the [[habitable zone]].<ref name="Alexander Venner et al (2026)" />

[[File:HD 137010_Earth_and_Mars.png|thumb|Size comparison of HD 137010 b with Earth and Mars]]

Its equilibrium temperature is approximately {{Val|205|17|28}} K (for a albedo of 0), potentially as low as 173 K for a higher albedo, this is colder than the average surface temperature of [[Mars]].<ref name="Alexander Venner et al (2026)" /> Models suggest a 40% probability of lying in the conservative habitable zone and 51% in the optimistic habitable zone, a thick CO₂-rich atmosphere could potentially allow liquid water despite the low insolation.<ref name="Alexander Venner et al (2026)" />

As of early 2026, HD 137010 b remains a planet candidate because only one transit has been observed, confirmation requires a second transit or supporting radial-velocity data.<ref name="Alexander Venner et al (2026)" /> The host star's brightness (V = 10.14) makes it an excellent target for future follow-up observations.<ref name="Alexander Venner et al (2026)" />

{{OrbitboxPlanet begin | table_ref =<ref name="Martin-2026" /><ref name="Alexander Venner et al (2026)" /> }} {{OrbitboxPlanet hypothetical | exoplanet = [[HD 137010 b|b]] | radius_earth = {{Val|1.06|0.06|0.05}} | period = {{val|355.0|200.0|59.0}} | eccentricity = 0 | semimajor = {{val|0.88|0.3|0.1}} | inclination = {{val|89.82|0.05|0.03|p=>}} | status = unconfirmed }} {{Orbitbox end}} {{clear left}}

==References== {{Reflist}}

[[Category:Libra (constellation)]] [[Category:K-type main-sequence stars]] [[Category:Hypothetical planetary systems]] [[Category:Henry Draper Catalogue objects|137010]] [[Category:Hipparcos objects|075398]]