# HD 176693

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/HD_176693
> Markdown URL: https://mediated.wiki/source/HD_176693.md
> Source: https://en.wikipedia.org/wiki/HD_176693
> Source revision: 1324297747
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Star in the constellation Draco

HD 176693 Observation data Epoch J2000 Equinox J2000 Constellation Draco[1] Right ascension 18h 59m 08.684s[2] Declination 48° 25′ 23.60″[2] Apparent magnitude (V) 8.83[3] Characteristics Evolutionary stage Main sequence Spectral type F8V[4] B−V color index 0.51[5] Astrometry Radial velocity (Rv) −54.76±0.18[6] km/s Proper motion (μ) RA: 4.704±0.013 mas/yr[2] Dec.: 9.263±0.016 mas/yr[2] Parallax (π) 11.2176±0.0126 mas[2] Distance 290.8 ± 0.3 ly (89.1 ± 0.1 pc) Details[7] Mass 1.05±0.04 M☉ Radius 1.253±0.051 R☉ Luminosity 1.864[8] L☉ Surface gravity (log g) 4.318+0.08 −0.089 cgs Temperature 6,080±65 K Metallicity [Fe/H] −0.138+0.043 −0.042 dex Rotation 12.89±0.19 d Rotational velocity (v sin i) 2.8±1.0 km/s Age 7.15±1.61[5] Gyr Other designations BD+48 2806, HD 176693, Kepler-408, KOI-1612, KIC 10963065, TYC 3545-1227-1, GSC 03545-01227, 2MASS J18590868+4825236, Gaia EDR3 2131593785132997632[9] Database references SIMBAD data

**HD 176693**, also known as **Kepler-408**, is a [star](/source/Star) with a close orbiting [exoplanet](/source/Exoplanet) in the northern [constellation](/source/Constellation) of [Draco](/source/Draco_(constellation)). It is located at a distance of 291 [light years](/source/Light_year) from the Sun based on [parallax](/source/Stellar_parallax) measurements, but it is drifting closer with a [radial velocity](/source/Radial_velocity) of −55 km/s.[6] The star is predicted to come as close as 23.1 light-years in 1.6 million years.[10] It has an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 8.83,[3] which is too faint to be viewed with the naked eye.

The [spectrum](/source/Stellar_spectrum) of HD 176693 matches an [F-type main-sequence star](/source/F-type_main-sequence_star) with a [stellar classification](/source/Stellar_classification) of F8V.[4] The star is older than the Sun, at 7.15 billion years. It is slightly and uniformly[11] depleted in heavy elements compared to the Sun, having about 75% of the solar abundance of iron and other heavy elements.[7] HD 176693 is a [chromospherically](/source/Chromosphere) [inactive](/source/Magnetic_activity) star,[5] although there is weak evidence for [tidal spin-up](/source/Tidal_acceleration) due to star-planet interaction.[12]

HD 176693 is 5% more massive than the Sun and has a 25% larger radius.[7] It is radiating 1.9[8] times the luminosity of the Sun from its [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 6,080 K. The star is spinning with a [rotation period](/source/Rotation_period) of 12.89 days.[7] As of 2016, multiplicity surveys have not detect any stellar companions to HD 176693.[13]

## Planetary system

In 2014, a [transiting](/source/Transit_(astronomy)) [Sub-Earth](/source/Sub-Earth) planet [b](/source/Kepler-408b) was detected on a tight 2.5 day orbit. Initially reported with a relatively low confidence of 97.9%,[14] it was confirmed in 2016.[15]

The planetary orbit is inclined to the equatorial plane of the star by 41.7+5.1 −3.5°. Such strong spin-orbit misalignment is unique for a sub-Earth transiting planet, and needs either additional giant planets in the system or a history of close stellar encounters to explain it.[7] The planet may also be a captured body originating from elsewhere.[16]

The Kepler-408 planetary system[7] Companion (in order from star) Mass Semimajor axis (AU) Orbital period (days) Eccentricity Inclination (°) Radius b ≥ 0.02[14] MJ — 2.465024±0.000005 — 81.85±0.10 0.86±0.04 R🜨

## References

1. **[^](#cite_ref-Roman1987_1-0)** [Roman, Nancy G.](/source/Nancy_Roman) (1987). ["Identification of a constellation from a position"](https://doi.org/10.1086%2F132034). *[Publications of the Astronomical Society of the Pacific](/source/Publications_of_the_Astronomical_Society_of_the_Pacific)*. **99** (617): 695. [Bibcode](/source/Bibcode_(identifier)):[1987PASP...99..695R](https://ui.adsabs.harvard.edu/abs/1987PASP...99..695R). [doi](/source/Doi_(identifier)):[10.1086/132034](https://doi.org/10.1086%2F132034). [Constellation record for this object](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?source=VI%2F42%2Fout&%2F%2Ftables=VI%2F42%2Fout&-c=Kepler-408&-c.eq=J2000&-c.r=++2&-c.u=arcmin&-c.geom=r&-source=&-source=VI%2F42%2Fout&-out=RA1875&-out=DE1875&-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) 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%3D2131593785132997632%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Høg_et_al_2000_3-0) [***b***](#cite_ref-Høg_et_al_2000_3-1) Høg, E.; et al. (March 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), [doi](/source/Doi_(identifier)):[10.1888/0333750888/2862](https://doi.org/10.1888%2F0333750888%2F2862).

1. ^ [***a***](#cite_ref-Molenda-Żakowicz_et_al_2013_4-0) [***b***](#cite_ref-Molenda-Żakowicz_et_al_2013_4-1) Molenda-Żakowicz, J.; et al. (2013), "Atmospheric parameters of 169 F-, G-, K- and M-type stars in the Kepler field", *Monthly Notices of the Royal Astronomical Society*, **434** (2): 1422, [arXiv](/source/ArXiv_(identifier)):[1306.6011](https://arxiv.org/abs/1306.6011), [Bibcode](/source/Bibcode_(identifier)):[2013MNRAS.434.1422M](https://ui.adsabs.harvard.edu/abs/2013MNRAS.434.1422M), [doi](/source/Doi_(identifier)):[10.1093/mnras/stt1095](https://doi.org/10.1093%2Fmnras%2Fstt1095), [S2CID](/source/S2CID_(identifier)) [59269553](https://api.semanticscholar.org/CorpusID:59269553).

1. ^ [***a***](#cite_ref-Booth2019_5-0) [***b***](#cite_ref-Booth2019_5-1) [***c***](#cite_ref-Booth2019_5-2) Booth, R. S.; et al. (2020), "Chromospheric emission of solar-type stars with asteroseismic ages", *Monthly Notices of the Royal Astronomical Society*, **491** (1): 455–467, [arXiv](/source/ArXiv_(identifier)):[1910.12557](https://arxiv.org/abs/1910.12557), [Bibcode](/source/Bibcode_(identifier)):[2020MNRAS.491..455B](https://ui.adsabs.harvard.edu/abs/2020MNRAS.491..455B), [doi](/source/Doi_(identifier)):[10.1093/mnras/stz3039](https://doi.org/10.1093%2Fmnras%2Fstz3039).

1. ^ [***a***](#cite_ref-Gaia_2022_6-0) [***b***](#cite_ref-Gaia_2022_6-1) Gaia Collaboration (May 2022), "Gaia DR3 Part 1. Main source", *VizieR Online Data Catalog*, [Bibcode](/source/Bibcode_(identifier)):[2022yCat.1355....0G](https://ui.adsabs.harvard.edu/abs/2022yCat.1355....0G), [doi](/source/Doi_(identifier)):[10.26093/cds/vizier.1355](https://doi.org/10.26093%2Fcds%2Fvizier.1355).

1. ^ [***a***](#cite_ref-Kamiaka2019_7-0) [***b***](#cite_ref-Kamiaka2019_7-1) [***c***](#cite_ref-Kamiaka2019_7-2) [***d***](#cite_ref-Kamiaka2019_7-3) [***e***](#cite_ref-Kamiaka2019_7-4) [***f***](#cite_ref-Kamiaka2019_7-5) Kamiaka, Shoya; et al. (2019), "The Misaligned Orbit of the Earth-sized Planet Kepler-408b", *The Astronomical Journal*, **157** (4): 137, [arXiv](/source/ArXiv_(identifier)):[1902.02057](https://arxiv.org/abs/1902.02057), [Bibcode](/source/Bibcode_(identifier)):[2019AJ....157..137K](https://ui.adsabs.harvard.edu/abs/2019AJ....157..137K), [doi](/source/Doi_(identifier)):[10.3847/1538-3881/ab04a9](https://doi.org/10.3847%2F1538-3881%2Fab04a9), [S2CID](/source/S2CID_(identifier)) [118909208](https://api.semanticscholar.org/CorpusID:118909208).

1. ^ [***a***](#cite_ref-Brito_Lopes_2019_8-0) [***b***](#cite_ref-Brito_Lopes_2019_8-1) Brito, Ana; Lopes, Ilídio (2019), "The partial ionization zone of heavy elements in F-stars: A study on how it correlates with rotation", *Monthly Notices of the Royal Astronomical Society*, **488** (2): 1558–1571, [arXiv](/source/ArXiv_(identifier)):[1906.12308](https://arxiv.org/abs/1906.12308), [Bibcode](/source/Bibcode_(identifier)):[2019MNRAS.488.1558B](https://ui.adsabs.harvard.edu/abs/2019MNRAS.488.1558B), [doi](/source/Doi_(identifier)):[10.1093/mnras/stz1804](https://doi.org/10.1093%2Fmnras%2Fstz1804).

1. **[^](#cite_ref-SIMBAD_9-0)** ["Kepler-408"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Kepler-408), *[SIMBAD](/source/SIMBAD)*, [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg), retrieved 1 July 2021

1. **[^](#cite_ref-Bailer-Jones_et_al_2018_10-0)** Bailer-Jones, C.A.L.; et al. (2018), "New stellar encounters discovered in the second Gaia data release", *Astronomy & Astrophysics*, **616**: A37, [arXiv](/source/ArXiv_(identifier)):[1805.07581](https://arxiv.org/abs/1805.07581), [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A..37B](https://ui.adsabs.harvard.edu/abs/2018A&A...616A..37B), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833456](https://doi.org/10.1051%2F0004-6361%2F201833456), [S2CID](/source/S2CID_(identifier)) [56269929](https://api.semanticscholar.org/CorpusID:56269929).

1. **[^](#cite_ref-Ramírez_et_al_2020_11-0)** Ramírez, I.; et al. (2020), "Detailed chemical compositions of planet-hosting stars – I. Exploration of possible planet signatures", *Monthly Notices of the Royal Astronomical Society*, **495** (4): 3961–3973, [arXiv](/source/ArXiv_(identifier)):[2005.09846](https://arxiv.org/abs/2005.09846), [Bibcode](/source/Bibcode_(identifier)):[2020MNRAS.495.3961L](https://ui.adsabs.harvard.edu/abs/2020MNRAS.495.3961L), [doi](/source/Doi_(identifier)):[10.1093/mnras/staa1420](https://doi.org/10.1093%2Fmnras%2Fstaa1420).

1. **[^](#cite_ref-Metcalfe_Egeland_2019_12-0)** Metcalfe, Travis S.; Egeland, Ricky (2019), "Understanding the Limitations of Gyrochronology for Old Field Stars", *The Astrophysical Journal*, **871** (1): 39, [arXiv](/source/ArXiv_(identifier)):[1811.11905](https://arxiv.org/abs/1811.11905), [Bibcode](/source/Bibcode_(identifier)):[2019ApJ...871...39M](https://ui.adsabs.harvard.edu/abs/2019ApJ...871...39M), [doi](/source/Doi_(identifier)):[10.3847/1538-4357/aaf575](https://doi.org/10.3847%2F1538-4357%2Faaf575), [S2CID](/source/S2CID_(identifier)) [119405127](https://api.semanticscholar.org/CorpusID:119405127).

1. **[^](#cite_ref-Kraus_et_al_2016_13-0)** Kraus, Adam L.; et al. (2016), "The Impact of Stellar Multiplicity on Planetary Systems. I. The Ruinous Influence of Close Binary Companions", *The Astronomical Journal*, **152** (1): 8, [arXiv](/source/ArXiv_(identifier)):[1604.05744](https://arxiv.org/abs/1604.05744), [Bibcode](/source/Bibcode_(identifier)):[2016AJ....152....8K](https://ui.adsabs.harvard.edu/abs/2016AJ....152....8K), [doi](/source/Doi_(identifier)):[10.3847/0004-6256/152/1/8](https://doi.org/10.3847%2F0004-6256%2F152%2F1%2F8), [S2CID](/source/S2CID_(identifier)) [119110229](https://api.semanticscholar.org/CorpusID:119110229).

1. ^ [***a***](#cite_ref-Marcy_et_al_2014_14-0) [***b***](#cite_ref-Marcy_et_al_2014_14-1) Marcy, Geoffrey W.; et al. (2014), "Masses, Radii, and Orbits of Small Kepler Planets: The Transition from Gaseous to Rocky Planets", *The Astrophysical Journal Supplement Series*, **210** (2): 20, [arXiv](/source/ArXiv_(identifier)):[1401.4195](https://arxiv.org/abs/1401.4195), [Bibcode](/source/Bibcode_(identifier)):[2014ApJS..210...20M](https://ui.adsabs.harvard.edu/abs/2014ApJS..210...20M), [doi](/source/Doi_(identifier)):[10.1088/0067-0049/210/2/20](https://doi.org/10.1088%2F0067-0049%2F210%2F2%2F20), [S2CID](/source/S2CID_(identifier)) [10760418](https://api.semanticscholar.org/CorpusID:10760418).

1. **[^](#cite_ref-Campante_et_al_2016_15-0)** Campante, T. L.; et al. (2016), "Spin–Orbit Alignment of Exoplanet Systems: Ensemble Analysis Using Asteroseismology", *The Astrophysical Journal*, **819** (1): 85, [arXiv](/source/ArXiv_(identifier)):[1601.06052](https://arxiv.org/abs/1601.06052), [Bibcode](/source/Bibcode_(identifier)):[2016ApJ...819...85C](https://ui.adsabs.harvard.edu/abs/2016ApJ...819...85C), [doi](/source/Doi_(identifier)):[10.3847/0004-637X/819/1/85](https://doi.org/10.3847%2F0004-637X%2F819%2F1%2F85), [S2CID](/source/S2CID_(identifier)) [56307453](https://api.semanticscholar.org/CorpusID:56307453).

1. **[^](#cite_ref-Petrovich_et_al_2020_16-0)** Petrovich, Cristobal; et al. (2020), "A Disk-driven Resonance as the Origin of High Inclinations of Close-in Planets", *The Astrophysical Journal Letters*, **902** (1): L5, [arXiv](/source/ArXiv_(identifier)):[2008.08587](https://arxiv.org/abs/2008.08587), [Bibcode](/source/Bibcode_(identifier)):[2020ApJ...902L...5P](https://ui.adsabs.harvard.edu/abs/2020ApJ...902L...5P), [doi](/source/Doi_(identifier)):[10.3847/2041-8213/abb952](https://doi.org/10.3847%2F2041-8213%2Fabb952), [S2CID](/source/S2CID_(identifier)) [221186597](https://api.semanticscholar.org/CorpusID:221186597).

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

[Portals](https://en.wikipedia.org/wiki/Wikipedia:Contents/Portals):
- [Astronomy](https://en.wikipedia.org/wiki/Portal:Astronomy)
- [Stars](https://en.wikipedia.org/wiki/Portal:Stars)
- [Outer space](https://en.wikipedia.org/wiki/Portal:Outer_space)

---
Adapted from the Wikipedia article [HD 176693](https://en.wikipedia.org/wiki/HD_176693) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/HD_176693?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.