{{Short description|F-type star in the constellation Draco}} {{Starbox begin}} <!--{{Starbox image | image= }}--> {{Starbox observe | epoch = J2000 | constell = [[Draco (constellation)|Draco]]<ref name=XHIP/> | ra = {{RA|14|36|21.3187}}<ref name=GaiaDR3/> | dec = {{DEC|+57|33|38.382}}<ref name=GaiaDR3/> | appmag_v = {{Val|8.29|0.01}}<ref name=Hog2000/> }} {{Starbox character | type = [[main sequence]]<ref name=GaiaDR3/> | class = F8<ref name=Cannon1993/> | u-b = | b-v = }} {{Starbox astrometry | radial_v = {{val|-4.851|0.004}}<ref name=Jönsson2020/> | prop_mo_ra = {{val|-82.125}} | prop_mo_dec = +67.259 | pm_footnote = <ref name=GaiaDR3/> | parallax = 13.5609 | p_error = 0.0216 | parallax_footnote = <ref name=GaiaDR3/> | absmag_v = 4.16<ref name=Holmberg2009/> }} {{Starbox orbit | reference = <ref name=Pinamonti2025/> | period_unitless = {{val|9.37|0.06|0.05}} years | axis_unitless = {{Val|4.85|0.02|0.01|ul=au}} | eccentricity = {{Val|0.850|0.002}} | inclination = {{Val|130.3|1.6|1.9}} | node = {{Val|131.7|3.3|3.4}} | periarg = {{Val|−105.7|0.4|0.3}} | periastron = {{val|2023.6716|0.0009|fmt=none}} }} {{Starbox detail | source = <ref name=Pinamonti2025/> | component1 = A | mass = {{val|1.212|0.058|0.068}} | radius = {{Val|1.248|0.024}} | luminosity = {{Val|2.10|0.07}} | temperature = {{Val|6210|40|fmt=commas}} | gravity = {{Val|4.329|0.025|0.030}} | rotation = {{Val|7.8|0.6}} days | rotational_velocity = {{val|6.1|0.5}} | metal_fe = {{val|+0.16|0.08}} | age_gyr = {{Val|1.4|0.3}} | component2 = B | mass_mj2 = {{Val|19.8|0.5}} }} {{Starbox catalog | names = {{odlist |HD=128717 | HIP=71425 | BD=+58°1514 | TYC=3866-1234-1 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad=HD+128717 }} {{Starbox end}} '''HD 128717''' is a star in the constellation of [[Draco (constellation)|Draco]]. With an [[apparent magnitude]] of +8.29, it is too faint to be seen with the [[naked eye]]. [[Parallax]] measurements by the ''[[Gaia spacecraft|Gaia]]'' spacecraft imply a distance of {{convert|73.7|pc|ly|abbr=off|lk=on|order=flip}}. It is moving towards the Solar System at a velocity of 4.851 km/s.
==Characteristics== With a [[spectral class]] of F8,<ref name=Cannon1993/> HD 128717 is a [[late-type star|late-type]] [[F-type star]]. It is estimated to be 1.4 billion years old, has 1.21 times the [[mass of the Sun]] and 1.25 times the [[solar radius|radius]]. It radiates 2.1 times the [[Sun's luminosity]] from its [[photosphere]] at an [[effective temperature]] of {{val|6210|fmt=commas|ul=K}},<ref name=Pinamonti2025/> giving it the typical yellowish-white hue of a late-type F-type star.<ref name=csiro/>
The [[Space velocity (astronomy)|space velocity]] components of HD 128717 are {{Val|p=U =|-30}}, {{Val|p=V=|-10}} and {{Val|p=W=|-4}}km/s. It is orbiting the [[Milky Way]] galaxy with an [[orbital eccentricity]] of 0.06. Its distance from the [[Galactic Center]] varies between {{convert|7.40|kpc|kly|abbr=off}} and {{convert|8.38|kpc|kly|abbr=on}}. This orbit lies close to the [[galactic plane]], and the star travels no more than {{convert|70|pc|ly|abbr=off}} above or below this plane.<ref name=Nordstrom2004/>
==Companion== [[Astrometry|Astrometric]] data collected by the ''[[Gaia spacecraft|Gaia]]'' spacecraft on its [[Gaia DR3|third data release]] 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,<ref name=Gaia2022/> and the paper by Sahlmann et al in 2024 identified HD 128717 "as a strong candidate for hosting a super-Jupiter".<ref name=Sahlmann2024/> In the same year, Alessandro Sozzetti reported, in a conference, the confirmation of the object using [[radial velocity]] observations.<ref name=Sozzetti2024/> 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.<ref name=Pinamonti2025/>
HD 128717 b is a [[brown dwarf]] with 19.8 times the [[mass of Jupiter]]. It has an orbital period of 9.37 years and a highly-[[eccentric orbit]]: At [[apoastron]], its orbital separation is 9.0 [[astronomical unit]]s, while at [[periastron]] it is 0.73 au.{{Efn|Calculating using the equations ''a''(1 + ''e'') and ''a''(1 − e) for [[apoastron]] and [[periastron]], respectively, where ''a'' is the semi-major axis and ''e'' is the eccentricity.}} The reasons for such a high eccentricity remain unclear.<ref name=Pinamonti2025/>
==Notes== {{notelist}}
==References== <references>
<ref name=XHIP>{{Cite XHIP|71425}}</ref>
<ref name=SIMBAD>{{Cite SIMBAD|title=HD 128717}}</ref>
<ref name=GaiaDR3>{{Cite DR3|1610837178107032192}}</ref>
<ref name=Hog2000>{{Cite journal |last1=Høg |first1=E. |last2=Fabricius |first2=C. |last3=Makarov |first3=V. V. |last4=Urban |first4=S. |last5=Corbin |first5=T. |last6=Wycoff |first6=G. |last7=Bastian |first7=U. |last8=Schwekendiek |first8=P. |last9=Wicenec |first9=A. |year=2000 |title=The Tycho-2 catalogue of the 2.5 million brightest stars |bibcode=2000A&A...355L..27H |journal=Astronomy and Astrophysics |language=en |volume=355 |pages=L27–L30 |issn=0004-6361}}</ref>
<ref name=Cannon1993>{{Cite journal |last1=Cannon |first1=A. J. |last2=Pickering |first2=E. C. |year=1993 |title=VizieR Online Data Catalog: Henry Draper Catalogue and Extension (Cannon+ 1918-1924; ADC 1989) |journal=VizieR Online Data Catalog |bibcode=1993yCat.3135....0C |language=en |volume=3135 |pages=III/135A}}</ref>
<ref name=Gaia2022>{{Cite journal |last1=Collaboration |first1=Gaia |last2=Arenou |first2=F. |last3=Babusiaux |first3=C. |last4=Barstow |first4=M. A. |last5=Faigler |first5=S. |last6=Jorissen |first6=A. |last7=Kervella |first7=P. |last8=Mazeh |first8=T. |last9=Mowlavi |first9=N. |last10=Panuzzo |first10=P. |last11=Sahlmann |first11=J. |last12=Shahaf |first12=S. |last13=Sozzetti |first13=A. |last14=Bauchet |first14=N. |last15=Damerdji |first15=Y. |date=2022-06-11 |title=Gaia Data Release 3. Stellar multiplicity, a teaser for the hidden treasure |journal=Astronomy and Astrophysics |language=en |volume=674 |pages=A34 |doi=10.1051/0004-6361/202243782 |arxiv=2206.05595 |bibcode=2023A&A...674A..34G |issn=0004-6361}}</ref>
<ref name=Pinamonti2025>{{cite journal |last1=Pinamonti |first1=M. |last2=Sozzetti |first2=A. |last3=Barbato |first3=D. |last4=Desidera |first4=S. |last5=Biazzo |first5=K. |last6=Bonomo |first6=A. S. |last7=Lanza |first7=A. F. |last8=Naponiello |first8=L. |last9=Affer |first9=L. |title=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 |date=2025-12-04 |arxiv=2512.04606 |journal=Astronomy and Astrophysics}}</ref>
<ref name=Sahlmann2024>{{Cite journal |last1=Sahlmann |first1=Johannes |last2=Gómez |first2=Pablo |date=2024-04-14 |title=Machine learning-based identification of Gaia astrometric exoplanet orbits |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=537 |issue=2 |pages=1130–1145 |doi=10.1093/mnras/staf018 |doi-access=free |issn=0035-8711 |arxiv=2404.09350}}</ref>
<ref name=Sozzetti2024>{{Cite journal |last=Sozzetti |first=Alessandro |date=July 2024 |title=Ground-based RV follow-up of Gaia DR3 astrometric exoplanet candidates around bright stars |journal=EAS2024, European Astronomical Society Annual Meeting |language=en |pages=1626 |bibcode=2024eas..conf.1626S }}</ref>
<ref name=Jönsson2020>{{Cite journal |last1=Jönsson |first1=Henrik |last2=Holtzman |first2=Jon A. |last3=Prieto |first3=Carlos Allende |last4=Cunha |first4=Katia |last5=García-Hernández |first5=D. A. |last6=Hasselquist |first6=Sten |last7=Masseron |first7=Thomas |last8=Osorio |first8=Yeisson |last9=Shetrone |first9=Matthew |last10=Smith |first10=Verne |last11=Stringfellow |first11=Guy S. |last12=Bizyaev |first12=Dmitry |last13=Edvardsson |first13=Bengt |last14=Majewski |first14=Steven R. |last15=Mészáros |first15=Szabolcs |date=2020-08-17 |title=APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South |journal=The Astronomical Journal |volume=160 |issue=3 |pages=120 |doi=10.3847/1538-3881/aba592 |arxiv=2007.05537 |bibcode=2020AJ....160..120J |doi-access=free |issn=0004-6256}}</ref>
<ref name=Nordstrom2004>{{Cite journal |last1=Nordström |first1=B. |last2=Mayor |first2=M. |last3=Andersen |first3=J. |last4=Holmberg |first4=J. |last5=Pont |first5=F. |last6=Jørgensen |first6=B. R. |last7=Olsen |first7=E. H. |last8=Udry |first8=S. |last9=Mowlavi |first9=N. |date=May 2004 |title=The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ∼14 000 F and G dwarfs |journal=Astronomy and Astrophysics |language=en |volume=418 |pages=989–1019 |doi=10.1051/0004-6361:20035959 |arxiv=astro-ph/0405198 |bibcode=2004A&A...418..989N |issn=0004-6361}}</ref>
<ref name=Holmberg2009>{{Cite journal |last1=Holmberg |first1=J. |last2=Nordström |first2=B. |last3=Andersen |first3=J. |date=July 2009 |title=The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics |journal=Astronomy and Astrophysics |language=en |volume=501 |issue=3 |pages=941–947 |doi=10.1051/0004-6361/200811191 |arxiv=0811.3982 |bibcode=2009A&A...501..941H |issn=0004-6361}}</ref>
<ref name=csiro>{{cite web | title=The Colour of Stars | date=December 21, 2004 | work=Australia Telescope, Outreach and Education | publisher=Commonwealth Scientific and Industrial Research Organisation | url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | accessdate=2012-01-16 | archive-date=2013-12-03 | archive-url=https://web.archive.org/web/20131203222826/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | url-status=dead }}</ref>
</references> {{Stars of Draco}} [[Category:Henry Draper Catalogue objects|128717]] [[Category:Hipparcos objects|071425]] [[Category:Draco (constellation)]] [[Category:F-type main-sequence stars]] [[Category:Brown dwarfs]] [[Category:Durchmusterung objects|+58 1514]]