7 Draconis
{{Short description|Star in the constellation Draco}}
{{Starbox begin
| name = 7 Draconis
}}
{{Starbox observe
| epoch = J2000.0
| constell = Draco
| dec = {{DEC|+66|47|25.0977}}
}}
{{Starbox character
| u-b =
| r-i =
| variable =
}}
{{Starbox astrometry
| parallax = 4.1601
| p_error = 0.1056
}}
{{Starbox detail
| source =
| mass =
| gravity =
| metal_fe =
| rotational_velocity =
| age_myr =
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{{Starbox catalog
| names = {{odlist | name=Tianyi | F=7 Dra | BD=+67°764 | FK5=3020 | HD=111335 | HIP=62423 | HR=4863 | SAO=15902 }}
}}
{{Starbox reference
| Simbad = 7+Dra
}}
{{Starbox end}}
7 Draconis, also named Tianyi {{IPAc-en|t|i|æ|n|ˈ|j|iː}}, is a single star in the northern circumpolar constellation of Draco. It is visible to the naked eye as a faint orange-hued star with a stellar classification of 5.43. Based upon an annual parallax shift of {{Val|4.16|ul=mas}} as seen from the Earth, the star is located approximately 780 light-years from the Sun.
This is an evolved giant star with a stellar classification of K5 III. The measured angular diameter of this star, after correction for limb darkening, is {{val|2.61|0.03|ul=mas}}. At its estimated distance, this yields a physical size of about 67 times the radius of the Sun. It is radiating about 1,024 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,945 K.
Nomenclature
7 Draconis is the star's Flamsteed designation.
The star bore the traditional Chinese name of Tianyi,{{cite web | url=https://exopla.net/wp-content/uploads/2025/04/2018_WGSN-triennial-report-2015-2018.pdf | page=7 | title=WG Triennial Report (2015-2018) - Star Names |access-date=2018-07-14}} from 天乙 (Tiān Yǐ) or 天一 (Tiān Yī, the Celestial Great One), a deity in Taoism. Alternatively, Tianyi may refer to 10 Draconis{{cn|date=May 2025|reason=Poorly sourced identification appearing elsewhere on English and Chinese Wikipedias}} or κ Draconis, with 7 and 8 Draconis forming Neichu, representing a private kitchen. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Tianyi for this star on 30 June 2017 and it is now so entered in the IAU Catalog of Star Names.
References
{{reflist|refs=
{{cite simbad | title=6 Dra | access-date=2019-01-23 }}
{{Cite Gaia DR2|1683112784684915456}}
| title=XHIP: An extended hipparcos compilation
| last1=Anderson | first1=E. | last2=Francis | first2=Ch.
| journal=Astronomy Letters
| volume=38 | issue=5 | pages=331 | year=2012
| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015
| arxiv=1108.4971 | s2cid=119257644 | postscript=. }}
| last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A.
| title=A catalogue of multiplicity among bright stellar systems
| journal=Monthly Notices of the Royal Astronomical Society
| volume=389 | issue=2 | pages=869–879 | year=2008
| arxiv=0806.2878 | bibcode=2008MNRAS.389..869E
| doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | s2cid=14878976 | postscript=. }}
| url=https://www.iau.org/public/themes/naming_stars/
| title=Naming Stars
|publisher=IAU.org
|access-date=16 December 2017
|archive-url=https://web.archive.org/web/20250224122744/https://www.iau.org/public/themes/naming_stars/
|archive-date=24 February 2025
|url-status=dead}}
|url=https://www.iau.org/science/scientific_bodies/working_groups/280/
|title=International Astronomical Union {{!}} IAU
|website=www.iau.org
|access-date=2018-01-16}}
| last1=Richichi | first1=A. | last2=Percheron | first2=I.
| last3=Khristoforova | first3=M.
| title=CHARM2: An updated Catalog of High Angular Resolution Measurements
| journal=Astronomy and Astrophysics | postscript=.
| volume=431 | issue=2 | pages=773–777 | date=February 2005
| doi=10.1051/0004-6361:20042039 | bibcode=2005A&A...431..773R | doi-access=free }}
| first1=Kenneth R. | last1=Lang
| title=Astrophysical formulae | volume=1 | series=Astronomy and astrophysics library
| edition=3rd | publisher=Birkhäuser
| date=2006 | isbn=3-540-29692-1 | postscript=.
| url=https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41 }} The radius (R*) is given by:
:
& = \frac{(240\cdot 2.61\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\
& \approx 134.7\cdot R_{\bigodot}
\end{align}
| display-authors=1 | last1=McDonald | first1=I.
| last2=Zijlstra | first2=A. A. | last3=Boyer | first3=M. L.
| title=Fundamental parameters and infrared excesses of Hipparcos stars
| journal=Monthly Notices of the Royal Astronomical Society
| volume=427 | pages=343–357 | year=2012 | issue=1 | postscript=.
| doi=10.1111/j.1365-2966.2012.21873.x
| doi-access=free | bibcode=2012MNRAS.427..343M | arxiv=1208.2037 | s2cid=118665352 }}
{{cite journal |last1=Bonnet-Bidaud |first1=Jean-Marc |last2=Praderie |first2=Françoise |last3=Whitfield |first3=Susan |date=March 2009 |title=The Dunhuang Chinese sky: A comprehensive study of the oldest known star atlas |journal=Journal of Astronomical History and Heritage |volume=12 |issue=1 |pages=39–59 |doi= 10.3724/SP.J.1440-2807.2009.01.04|arxiv=0906.3034 |bibcode=2009JAHH...12...39B}}
{{cite journal |last1=Yang |first1=Bo-Shun |last2=Hoffmann |first2=Susanne M. |date=December 2024 |title=Identification of Z Cam's Historical Counterpart: The Quest for an Ancient Nova |journal=Research in Astronomy and Astrophysics |volume=24 |issue=12 |pages=125004 |doi=10.1088/1674-4527/ad89aa |arxiv=2410.19010 |bibcode=2024RAA....24l5004Y}}
}}
{{Stars of Draco|state=collapsed}}
{{Authority control}}
{{DEFAULTSORT:7 Draconis}}