# HD 128717

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F-type star in the constellation Draco

HD 128717 Observation data Epoch J2000 Equinox J2000 Constellation Draco[1] Right ascension 14h 36m 21.3187s[2] Declination +57° 33′ 38.382″[2] Apparent magnitude (V) 8.29±0.01[3] Characteristics Evolutionary stage main sequence[2] Spectral type F8[4] Astrometry Radial velocity (Rv) −4.851±0.004[5] km/s Proper motion (μ) RA: −82.125 mas/yr[2] Dec.: +67.259 mas/yr[2] Parallax (π) 13.5609±0.0216 mas[2] Distance 240.5 ± 0.4 ly (73.7 ± 0.1 pc) Absolute magnitude (MV) 4.16[6] Orbit[7] Period (P) 9.37+0.06 −0.05 years Semi-major axis (a) 4.85+0.02 −0.01 au Eccentricity (e) 0.850±0.002 Inclination (i) 130.3+1.6 −1.9° Longitude of the node (Ω) 131.7+3.3 −3.4° Periastron epoch (T) 2023.6716±0.0009 Argument of periastron (ω) (secondary) −105.7+0.4 −0.3° Details[7] A Mass 1.212+0.058 −0.068 M☉ Radius 1.248±0.024 R☉ Luminosity 2.10±0.07 L☉ Surface gravity (log g) 4.329+0.025 −0.030 cgs Temperature 6,210±40 K Metallicity [Fe/H] +0.16±0.08 dex Rotation 7.8±0.6 days Rotational velocity (v sin i) 6.1±0.5 km/s Age 1.4±0.3 Gyr B Mass 19.8±0.5 MJup Other designations BD+58°1514, HD 128717, HIP 71425, TYC 3866-1234-1[8] Database references SIMBAD data

**HD 128717** is a star in the constellation of [Draco](/source/Draco_(constellation)). With an [apparent magnitude](/source/Apparent_magnitude) of +8.29, it is too faint to be seen with the [naked eye](/source/Naked_eye). [Parallax](/source/Parallax) measurements by the *[Gaia](/source/Gaia_spacecraft)* spacecraft imply a distance of 240 [light-years](/source/Light-year) (73.7 [parsecs](/source/Parsec)). It is moving towards the Solar System at a velocity of 4.851 km/s.

## Characteristics

With a [spectral class](/source/Spectral_class) of F8,[4] HD 128717 is a [late-type](/source/Late-type_star) [F-type star](/source/F-type_star). It is estimated to be 1.4 billion years old, has 1.21 times the [mass of the Sun](/source/Mass_of_the_Sun) and 1.25 times the [radius](/source/Solar_radius). It radiates 2.1 times the [Sun's luminosity](/source/Sun's_luminosity) from its [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 6,210 [K](/source/Kelvin),[7] giving it the typical yellowish-white hue of a late-type F-type star.[9]

The [space velocity](/source/Space_velocity_(astronomy)) components of HD 128717 are U =−30, V=−10 and W=−4km/s. It is orbiting the [Milky Way](/source/Milky_Way) galaxy with an [orbital eccentricity](/source/Orbital_eccentricity) of 0.06. Its distance from the [Galactic Center](/source/Galactic_Center) varies between 7.40 kiloparsecs (24.1 kilolight-years) and 8.38 kpc (27.3 kly). This orbit lies close to the [galactic plane](/source/Galactic_plane), and the star travels no more than 70 parsecs (230 light-years) above or below this plane.[10]

## Companion

[Astrometric](/source/Astrometry) data collected by the *[Gaia](/source/Gaia_spacecraft)* spacecraft on its [third data release](/source/Gaia_DR3) revealed that HD 128717 appears to wobble around an empty space, indicating that it has an object in orbit whose gravitational force is pulling it. The object was first noted by the Gaia team in 2022,[11] and the paper by Sahlmann et al in 2024 identified HD 128717 "as a strong candidate for hosting a super-Jupiter".[12] In the same year, Alessandro Sozzetti reported, in a conference, the confirmation of the object using [radial velocity](/source/Radial_velocity) observations.[13] The companion was independently confirmed by Pinamonti *et al.* (2025), which named it as **Gaia-6b** since it was the sixth planetary candidate detected by Gaia that has been later confirmed.[7]

HD 128717 b is a [brown dwarf](/source/Brown_dwarf) with 19.8 times the [mass of Jupiter](/source/Mass_of_Jupiter). It has an orbital period of 9.37 years and a highly-[eccentric orbit](/source/Eccentric_orbit): At [apoastron](/source/Apoastron), its orbital separation is 9.0 [astronomical units](/source/Astronomical_unit), while at [periastron](/source/Periastron) it is 0.73 au.[a] The reasons for such a high eccentricity remain unclear.[7]

## Notes

1. **[^](#cite_ref-14)** Calculating using the equations *a*(1 + *e*) and *a*(1 − e) for [apoastron](/source/Apoastron) and [periastron](/source/Periastron), respectively, where *a* is the semi-major axis and *e* is the eccentricity.

## References

1. **[^](#cite_ref-XHIP_1-0)** Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". *[Astronomy Letters](/source/Astronomy_Letters)*. **38** (5): 331. [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971). [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A). [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015). [XHIP record for this object](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-ref=VIZ681510a8389ecb&-out.src=V%2F137D%2FXHIP&-nav=cat%3AV%2F137D%26tab%3A{V%2F137D%2FXHIP}%26key%3Asource%3DV%2F137D%2FXHIP%26HTTPPRM%3A&-source=V%2F137D%2FXHIP&-out=HIP&HIP=71425&-out=Comp&-out=Gr&-out=RAJ2000&-out=DEJ2000&-out=Dist&-out=X&-out=Y&-out=Z&-out=SpType&-out=Simbad&-out=Hpmag&-out=Lum&-out=Cst) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-GaiaDR3_2-0) [***b***](#cite_ref-GaiaDR3_2-1) [***c***](#cite_ref-GaiaDR3_2-2) [***d***](#cite_ref-GaiaDR3_2-3) [***e***](#cite_ref-GaiaDR3_2-4) Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D1610837178107032192%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. **[^](#cite_ref-Hog2000_3-0)** Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". *Astronomy and Astrophysics*. **355**: L27–L30. [Bibcode](/source/Bibcode_(identifier)):[2000A&A...355L..27H](https://ui.adsabs.harvard.edu/abs/2000A&A...355L..27H). [ISSN](/source/ISSN_(identifier)) [0004-6361](https://search.worldcat.org/issn/0004-6361).

1. ^ [***a***](#cite_ref-Cannon1993_4-0) [***b***](#cite_ref-Cannon1993_4-1) Cannon, A. J.; Pickering, E. C. (1993). "VizieR Online Data Catalog: Henry Draper Catalogue and Extension (Cannon+ 1918-1924; ADC 1989)". *VizieR Online Data Catalog*. **3135**: III/135A. [Bibcode](/source/Bibcode_(identifier)):[1993yCat.3135....0C](https://ui.adsabs.harvard.edu/abs/1993yCat.3135....0C).

1. **[^](#cite_ref-Jönsson2020_5-0)** Jönsson, Henrik; Holtzman, Jon A.; Prieto, Carlos Allende; Cunha, Katia; García-Hernández, D. A.; Hasselquist, Sten; Masseron, Thomas; Osorio, Yeisson; Shetrone, Matthew; Smith, Verne; Stringfellow, Guy S.; Bizyaev, Dmitry; Edvardsson, Bengt; Majewski, Steven R.; Mészáros, Szabolcs (2020-08-17). ["APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South"](https://doi.org/10.3847%2F1538-3881%2Faba592). *The Astronomical Journal*. **160** (3): 120. [arXiv](/source/ArXiv_(identifier)):[2007.05537](https://arxiv.org/abs/2007.05537). [Bibcode](/source/Bibcode_(identifier)):[2020AJ....160..120J](https://ui.adsabs.harvard.edu/abs/2020AJ....160..120J). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/aba592](https://doi.org/10.3847%2F1538-3881%2Faba592). [ISSN](/source/ISSN_(identifier)) [0004-6256](https://search.worldcat.org/issn/0004-6256).

1. **[^](#cite_ref-Holmberg2009_6-0)** Holmberg, J.; Nordström, B.; Andersen, J. (July 2009). "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics". *Astronomy and Astrophysics*. **501** (3): 941–947. [arXiv](/source/ArXiv_(identifier)):[0811.3982](https://arxiv.org/abs/0811.3982). [Bibcode](/source/Bibcode_(identifier)):[2009A&A...501..941H](https://ui.adsabs.harvard.edu/abs/2009A&A...501..941H). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/200811191](https://doi.org/10.1051%2F0004-6361%2F200811191). [ISSN](/source/ISSN_(identifier)) [0004-6361](https://search.worldcat.org/issn/0004-6361).

1. ^ [***a***](#cite_ref-Pinamonti2025_7-0) [***b***](#cite_ref-Pinamonti2025_7-1) [***c***](#cite_ref-Pinamonti2025_7-2) [***d***](#cite_ref-Pinamonti2025_7-3) [***e***](#cite_ref-Pinamonti2025_7-4) Pinamonti, M.; Sozzetti, A.; Barbato, D.; Desidera, S.; Biazzo, K.; Bonomo, A. S.; Lanza, A. F.; Naponiello, L.; Affer, L. (2025-12-04). "The GAPS programme at TNG LXXI. HD 128717 B/Gaia-6 B: a long-period eccentric low-mass brown dwarf from astrometry and radial velocities". *Astronomy and Astrophysics*. [arXiv](/source/ArXiv_(identifier)):[2512.04606](https://arxiv.org/abs/2512.04606).

1. **[^](#cite_ref-SIMBAD_8-0)** ["HD 128717"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+128717). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg).

1. **[^](#cite_ref-csiro_9-0)** ["The Colour of Stars"](https://web.archive.org/web/20131203222826/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html). *Australia Telescope, Outreach and Education*. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. Archived from [the original](http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html) on 2013-12-03. Retrieved 2012-01-16.

1. **[^](#cite_ref-Nordstrom2004_10-0)** Nordström, B.; Mayor, M.; Andersen, J.; Holmberg, J.; Pont, F.; Jørgensen, B. R.; Olsen, E. H.; Udry, S.; Mowlavi, N. (May 2004). "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ∼14 000 F and G dwarfs". *Astronomy and Astrophysics*. **418**: 989–1019. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0405198](https://arxiv.org/abs/astro-ph/0405198). [Bibcode](/source/Bibcode_(identifier)):[2004A&A...418..989N](https://ui.adsabs.harvard.edu/abs/2004A&A...418..989N). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20035959](https://doi.org/10.1051%2F0004-6361%3A20035959). [ISSN](/source/ISSN_(identifier)) [0004-6361](https://search.worldcat.org/issn/0004-6361).

1. **[^](#cite_ref-Gaia2022_11-0)** Collaboration, Gaia; Arenou, F.; Babusiaux, C.; Barstow, M. A.; Faigler, S.; Jorissen, A.; Kervella, P.; Mazeh, T.; Mowlavi, N.; Panuzzo, P.; Sahlmann, J.; Shahaf, S.; Sozzetti, A.; Bauchet, N.; Damerdji, Y. (2022-06-11). "Gaia Data Release 3. Stellar multiplicity, a teaser for the hidden treasure". *Astronomy and Astrophysics*. **674**: A34. [arXiv](/source/ArXiv_(identifier)):[2206.05595](https://arxiv.org/abs/2206.05595). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A..34G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A..34G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243782](https://doi.org/10.1051%2F0004-6361%2F202243782). [ISSN](/source/ISSN_(identifier)) [0004-6361](https://search.worldcat.org/issn/0004-6361).

1. **[^](#cite_ref-Sahlmann2024_12-0)** Sahlmann, Johannes; Gómez, Pablo (2024-04-14). ["Machine learning-based identification of Gaia astrometric exoplanet orbits"](https://doi.org/10.1093%2Fmnras%2Fstaf018). *Monthly Notices of the Royal Astronomical Society*. **537** (2): 1130–1145. [arXiv](/source/ArXiv_(identifier)):[2404.09350](https://arxiv.org/abs/2404.09350). [doi](/source/Doi_(identifier)):[10.1093/mnras/staf018](https://doi.org/10.1093%2Fmnras%2Fstaf018). [ISSN](/source/ISSN_(identifier)) [0035-8711](https://search.worldcat.org/issn/0035-8711).

1. **[^](#cite_ref-Sozzetti2024_13-0)** Sozzetti, Alessandro (July 2024). "Ground-based RV follow-up of Gaia DR3 astrometric exoplanet candidates around bright stars". *EAS2024, European Astronomical Society Annual Meeting*: 1626. [Bibcode](/source/Bibcode_(identifier)):[2024eas..conf.1626S](https://ui.adsabs.harvard.edu/abs/2024eas..conf.1626S).

v t e Constellation of Draco List of stars in Draco Draco in Chinese astronomy Stars Bayer α (Thuban) β (Rastaban) γ (Eltanin) δ (Altais) ε (Tyl) ζ (Aldhibah) η (Athebyne) θ ι (Edasich) κ λ (Giausar) μ (Alrakis) ν (Kuma) ξ (Grumium) ο π ρ σ (Alsafi) τ υ φ χ ψ1 (Dziban) ψ2 ω Flamsteed 4 6 7 (Tianyi) 8 (Taiyi) 10 (i) 15 (A) 18 (g) 19 (h) 26 36 39 (b) 42 (Fafnir) 45 (d) 50 59 64 (e) 68 Variable TW YY AG BY CL CM CX DO EK HP V581 HR 3751 4126 4934 5811 6237 6518 6618 (Alruba) 6817 7137 7783 HD 109246 (Funi) 101364 128717 147379 156279 158259 176693 191939 Other 2MASS 1237+6526 2MASS J17554042+6551277 G 240-72 GD 356 Gliese 420 Gliese 625 Gliese 687 GRW +70 8247 Kepler-4 Kepler-10 Kepler-12 Kepler-90 Kepler-296 KOI-256 LP 71-82 Qatar-1 SDSS J1240+6710 Struve 2398 TOI-1136 WD 1856+534 WISE 1647+5632 WISE 1841+7000 Exoplanets HD 139357 b HD 167042 b ι Dra b (Hypatia) Kepler-4b Kepler-10b c Kepler-12b Kepler-90e f g h i Kepler-296b c d e f TOI-1452 b TrES-2b Star clusters LAMOST 1 Nebulae Cat's Eye Nebula NGC 6742 Galaxies NGC 3147 3197 3735 4121 4125 4221 4236 4319 4331 4332 4363 4441 4513 4545 4589 5678 5777 5866 5866B 5879 5905 5907 5949 5963 5965 5982 5985 6090 6248 6285 6286 6338 6340 6365 6373 6394 6412 6503 6505 6566 6621 6622 6670 6676 6786 6789 Other 1ES 1927+654 1ES 1959+650 3C 249.1 3C 305 3C 319 3C 343 3C 343.1 3C 351 3C 356 3C 371 3C 380 3C 390.3 3C 401 4C +72.26 4C 73.08 8C 1241+735 Abell 2218 BCG Bean galaxy Beaver galaxy BZQ J1727+5510 Draco Dwarf Draco II GB 1508+5714 Goldfish galaxy H1821+643 HFLS3 IERS B1946+708 IRAS F17179+5444 IRAS 18580+6527 J120011.1+680924.8 KKR 25 Markarian 817 Markarian 876 Original TRG PGC 39058 Porphyrion QSO B1823+568 RGZ J172749.5+534647 S5 1803+784 S5 2007+777 SDSS J1715+6008 Tadpole Galaxy UGC 9391 UGC 9405 UGC 11241 UGC 11411 WISEA J145223.62+611707.5 WN B1851+5707 Galaxy clusters Abell 2218 CL1358+62 Draco Supercluster NGC 5866 Group Astronomical events SN 2003jb SN 2005B SN 2016aps Swift J1644+57 Category

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Adapted from the Wikipedia article [HD 128717](https://en.wikipedia.org/wiki/HD_128717) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/HD_128717?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.